Losing Tin in the Dross - Truth or Myth?

[Andy_P]

It seems nonsense that tin will come out of your wheelweight solution if you don't flux, or you skim off the dross with too much vigor. Is the tin not bound with the antimony and lead in solution? How then can it just float to the surface?

Isn't the "shiny stuff" that's attached to the metal parts that are skimmed off lead/tin/antimony, and not just tin?

[Glen]

Convince yourself -- Melt a pot of WW and let it just sit. Watch the dross under good light as it sits there and bakes -- it will turn a golden color. That gold is the tin coming out of solution. Tin is the only component of that alloy that is golden colored, both the lead and antimony are silver.

[Lloyd Smale]

the tin i have is silver not gold colared. the only thing ive seen gold colared in a melt is traces of copper.

[Bass Ackward]

Andy,

Oxygen and heat are the catalyst.

If you are using a bottom pour set-up, cover the top of the melt with like kitty litter and tin oxidation drops to a virtual zero.

Where that really is a problem is when constantly agitating the melt with a dipper. Or when running your mix too hot, you can burn off tin. The rate of burn off increases significantly over 800 degrees.

Simply use a good carbon flux and you will recapture the vast majority of your tin.

[Lee W]

If you search patent 2235423 from here:

http://patft.uspto.gov/netahtml/PTO/srchnum.htm

He states tin is best removed by adding lead chloride and vigorous stirring to oxidize the tin . The molten bath should be between 1050 and 1200 F. The tin is removed as dross skimmed from the bath.

There is much more info there. Since we are trying not to remove tin, we should do nothing this guy suggests.
If you cannot open TIFF files, I can email you JPGs but they are over 1 meg each.

[leftiye]

Andy,

But it DO come out as an oxide, and if you skim it off and throw it away, it's gone. Chances are that it's still combined with oxides of lead, and antimony (just a guess).

Rosin will reduce it (take the oxygen out of it), and recombine it with the melt. You can actually see this happen, as it will disappear, leaving only the shiny metal, and the rosin that hasn't yet burned off. Rosin is a special case of organic flux that can do this, most others can't quite make the grade and actually reduce the oxides. I use rosin in conjunction with sawdust to flux with. when done, I leave it there to act as an oxygen barrier.

[3sixbits]

Here we go again. I think I have figured a way to settle this debate. Take a clean cast iron pot. Weight and record a quanity of tin (pure tin only please). bring the tin to what ever your pet casting temp is and hold that temp for however long it takes you to cast your normal pot of metal. Cool, and weight the contents of the pot. Record any loss. Please keep in mind that 900 digs and above if you are casting lead is not good for your health, so I would assume you will hold the temp below 900 degs.

[Ohio Rusty]

I keep wondering the same thing, that if the alloys can come out of your lead. When I melt lead for muzzleloading bullets (700-725 degrees) I also skim off the dross continually during the casting session. It's not a dross like dirt, more like a skin, not unlike a thin skin on chocolate pudding. When it is pulled off to the side to get skimmed off, the skin is wrinkled, obviously different than the molten silver metal that is below it. I usually end up with quite a bit discarded into a tuna can set aside to catch the 'skins'. I've examined this left over metal in the can and it seems definitely harder than the muzzleloading round ball that fall from the moulds. I've heard and read on other lists that it is impossible to take out any alloys at the fairly low temperatures we cast at. Yet it seems (lacking scientific proof) that we can actually do this. I have always been curious as to what I'm skimming off isn't some form of oxide that has combined with a harder alloy. I know I end up with lead ball extremely soft by doing the above. I'd like to test the 'skins' I skim off to see if they are actually harder than the ball I cast. Maybe the skimmings just appear harder doing the thumbnail scratch test since it is not in an organized solid like a musket ball.
Ohio Rusty

[montana_charlie]

Cool, and weight the contents of the pot. Record any loss.
You forgot to mention skimming off the 'scum' as it forms. Do you believe that there won't be any?

If you skim it off, and the contents still weigh the same...what was it?

If you skim it off and the contents weigh less...does that prove that it was oxidized tin?
CM

[leftiye]

3sixbits, I'll tell you the same thing you told me. Go get a book or two, and read them yourself, If it isn't too degrading to one of your stature.

[leftiye]

Ohio rusty,

In my humble opinion, what you are skimming off is mostly lead oxide. Seeing as you mention muzzle loader boolits, I figure you start with pure lead. Not exactly to be saying it can't be anything else, but except for any impurities it would have to be lead oxide. So, we have here a way of proving that it is not just the tin that oxidizes off. Oxides are probably harder than the parent metal as they interfere with the malleability of the metal, I'd guess.

Try fluxing it with sawdust, and rosin, and see if that works. Alternatively take a torch to it. Most of these kinds of dross will recombine with a hot enough flame. I use a mapp gas torch.

[Buckshot]

.............It is true that the constituents of a true solution, just like a lead-tin-antimony alloy can be, will NOT weight segregate in the pot while molten.

However, you WILL loose metal through oxidation if you skim off the surface and do not flux. If you have good clean ingots and melt them, what are you skimming off? Where does this 'skin' come from and what is it made up of? It's metal oxide, and since tin has the lowest melting point, it is the first to oxidize in the presence of oxygen.

Lots of chemical reactions take place at an elevated rate when heated. Take water for example. A container of it set out will slowly loose volumn due to evaporation, which you can't see. Raise the temp to 212* and you'll see it happening at a violent rate.

Lead kept outside will form a white powdery crust over time and this is lead oxide. Oxygen is a fantastic reducer and is very energetic. Very simply, heat excites the atoms of whatever is heated, and makes it much easier for oxygen to do what it does to various objects.

................Buckshot

[Andy_P]

Well said. Another reason to flux, and also to keep the melt temp to "just high enough" - keeps the zinc "turds" (as someone just coined them :) ) in the dross and minimizes the amount of tin that can oxidized and lost.

This is good to know, but might be moot to me. It seems like the proportion lost would be very small since I have a pot that holds over 75 lbs of molten metal and I ladle out about 40 lbs into ingots between fluxings and dross removal. I flux again in my 20 lb bottom pour, and add 2% tin anyways.

Thanks guys. :-D

[Ricochet]

Lead oxide at lead melting temperatures can be yellow colored, too.

I don't believe metallic tin can separate out of the melt, but it may well oxidize more readily and separate out that way. I doubt our pots are hot enough for much, if any, reduction of oxides to occur with our usual fluxes.

[montana_charlie]

However, you WILL loose metal through oxidation if you skim off the surface and do not flux.
This describes my belief. 3sixbits, what is yours?

I don't believe metallic tin can separate out of the melt, but it may well oxidize more readily and separate out that way.
Since tin's melting temperature is lower that lead's, I assume it will oxidise a bit faster than lead will...when the alloy is up at casting temperature.

If they oxidized at the same rate (and got skimmed off), you would lose some alloy, but the ratio would not change. But, I don't think that is the case.

I doubt our pots are hot enough for much, if any, reduction of oxides to occur with our usual fluxes.
Here we are...back at the scientific crux of our varying 'religions' about fluxing.

My 'faith' says, "If the 'scum' is oxidized metal, and if adding carbon makes it disappear back into the pot...without skimming it out...everything that was in my pot to start with is back in there, again."
If that doesn't qualify as 'reduction of oxides' (in the scientific sense) then maybe it must remain something like 'returning sinners to the flock' through prayer and FLUXING.
CM

[Ricochet]

Well, what I think the flux mainly does is make the oxide separate from the melt so it skims off more easily, with less bulk due to included metal. I've never seen the dross just "disappear" with fluxing, Rather, it turns to a light dry powder on top of the melt. I've also just skimmed the dross without fluxing. A lot of lead ends up in that skim.

[montana_charlie]

I've never seen the dross just "disappear" with fluxing, Rather, it turns to a light dry powder on top of the melt.
Aha! Now we're getting somewhere!
Perhaps a chemical analysis of the 'powder' is the only way to know for sure, but...

I use the stick method. As the wood is stirred around, it 'burns' slowly.
I mean that it chars, and very gradually disappears. After stirring (fluxing) many times, the stick becomes too short to use.

After scrubbing the pot walls and bottom, the 'scum' is still floating on top. I use the stick's end to rake it all into a little glob against the side of the pot.
Using the stick like a spatula, I scrub that glob down into the alloy, mashing it against the pot side.

(I picture this as forcefully introducing carbon (the charred surface of the stick) to the oxides...down in a hot zone, devoid of oxygen...and the smearing pressure makes certain the carbon is available to all of the glob's molecules.)

It takes two or three tries to make the whole glob disappear, after which there is a tiny bit of black-colored powder that returns to the surface to be dipped off.
I believe the powder is just 'char' which has been dislodged from the stick...and the amount is so small I would have to flux a dozen times to accumulate a quarter teaspoon of it. It's absolutely black, dry, and loose, and has no discernable weight...very different from the 'pounds of slag' I used to throw away.
CM

[Ricochet]

Pretty much what I see if I flux with wax or oil. The "pounds of slag" is lead clinging to those little oxide particles, I think.

[whisler]

I would have to agree with MontanaCharlie. As I understand the chemistry of the situation, when you introduce carbon in the form of sawdust etc, you will be putting in much more highly active carbon than is needed to combine with the oxides of lead/tin/antimony to reduce them. After the organic material burns off you are left with carbon black, which is a very light black powder.
If all you had to begin with was oxidized metals, then you will likely end up with carbon black. If the metal was not completely clean when you started, you end up with carbon black + ????
Anyway that's how I see it.

[leftiye]

Ricochet,

One source states that pitch/ rosin (and probably fluxing paste) will reduce tin oxide starting at - believe it or not- about 450 degrees fahrenheit. FWIW

There are two uses of the word fluxing one separates and removes impurities. This is the correct definition. The other involves removing the oxides from the dross, and thereby letting it return to the melt as pure metal. This is more correctly called reduction or refining.

Montana C, I really like your logic, It's just like mine!

[montana_charlie]

There are two uses of the word fluxing one separates and removes impurities. This is the correct definition. The other involves removing the oxides from the dross, and thereby letting it return to the melt as pure metal. This is more correctly called reduction or refining.
You left out one use...probably the most important one.

"To condition the metal, this is the primary reason for fluxing in the foundry and every where else for that matter."

Still waiting for the definition of 'condition'...
CM

[Lee]

Facts: Both carbon and hydrogen are excellent reducing agents. Either or both can remove the oxygen from a metal oxide, leaving pure metal and either carbon dioxide or hydrogen oxide(water).
Oxygen is an excellent oxidizing agent. That is why the "dross" or scum forms on the top of your melting pot. Your metal(s) are oxidizing.

Opinions: Just looking at reactivity charts, both tin and lead are very close together. I would surmise that their oxidation rates in air would be about the same. And thus, I would expect to find both lead oxide and tin oxide floating on top of the molten pot. And with similar oxidation rates, I would suspect about the same ratio of metals, as is in the melt.

Now from Wikipedia(everyone's source of "instant" knowledge!!) there are 2 definitions of flux;
1. flux seperates and removes the oxides and impurities from a molten metal.
2. flux reduces oxides of metals and introduces them back into the metal solution.

Then, since tin and lead are both easily reduced metals, and not too easily oxidized metals(both can be easily won from their ores, thats why the ancients knew of and used them) the next step in cleaning your pot is to introduce carbon and/or hydrogen. And that's where wood(cellulose) or organic fluxes come in. Both provide a ready source of carbon and/or hydrogen which combine with the oxygen from the oxides and reduce the compound to a metallic form. Hopefully, the stirring action exposes these small metal particles to the molten melt, and they dissolve back in the pot.

Kitty litter(various clays or clay like compounds) keeps your pot clean by forming a barrier from the oxygen in the air. No oxygen, no oxidation. Note that unless the kitty litter contains a readily available reducing agent, (carbon or hydrogen, for instance) it will be unable to convert(reduce) any metal oxides back into their parent metals.

BTW, a pot full of any molten metal, at a temperature such that it can oxidize, and possessing an oxide with a low vapor pressure(so the oxide doesn't boil off) will always GAIN weight as it oxidizes. You're starting with a given weight of metal, and you're adding something to it(oxygen). It will gain weight. (Its' density may decrease, which is why the dross floats to the top)

Personal opinion: I believe a combination of the above to be the most efficient way to go. Commercial organic fluxing compounds are designed to reduce the oxides back to metal efficiently, wooden sticks combining carbon with the means of intimately mixing with the dross, assist and enhance the process. Hopefully I'll run out of steam before I run out of my bottle of flux. And Kitty Litter? I just don't care for the mess. Besides the cat turds really stink up the room............Lee:wink:

[3sixbits]

You forgot to mention skimming off the 'scum' as it forms. Do you believe that there won't be any?

If you skim it off, and the contents still weigh the same...what was it?

If you skim it off and the contents weigh less...does that prove that it was oxidized tin?
CM

I have what was left of a trade from 1974 (a year before I got married) one little SAECO ingot of pure tin. I've used for a holder of pages to keep books open. It has no white powder on it. I must have worn it off with frequent handling. It does not mark the pages of my books (why I've kept it I guess.) The rest of the trade was old powder cans, Frankford arsenal primers etc. Some of this stuff was used for cover art for HANDLOADER magazine years ago. I have melted large quantities of tin to recast into more easily handled weights and sizes and have not found any dross to skim off. Some of the sticks I've melted that were two feet long had a polished look to them and when you bend them double they make a crinkling popping sound, but show no signs of any oxides. When ever I buy metal I always weight it when I'm ready to recast it it to the sizes I use to alloy from, and have never found any reduction in weight from tin. I find no residue from tin or scum of any kind. I'm not saying the metal does not oxidize, I'm saying I can not see any. This may be because it is invisible in the air????

[Buckshot]

...........3sixbits, "I'm not saying the metal does not oxidize, I'm saying I can not see any. This may be because it is invisible in the air????"

For our purposes here, since most of our casting IS done with alloys (unless for ML'ers using pure lead) our main concern is the loss of tin. As the most expensive part of the alloy as a constituent, and also very valuable as it encapsulates antimony structures at cooling, we really don't want to loose any.

At the temps we're casting at there won't be any metalics in the air to see. However you CAN see the oxides formed on the surface as a dull skin. Since tin is normally a small proportion of the metal in the part, it will also be a smaller proportion of the crud on the surface.

Not being a metalurgist I don't know for sure that tin may oxidize at a more rapid rate then either lead or antimony. But the fact does remain that it can be removed from the alloy by simply skimming the crud off without fluxing. In the days of the hot type or linotype machines, they had enrichment alloy that was higher in tin then the regular linotype alloy.

Obviously the tin is removed enough over time to have an effect on it's ability to cast type well. Over the years, so far as buying scrap linotype goes it was mentioned often to be wary of buying scrap where all the tin had been 'burned out'. I'm sure the tin had not been burned out but rather skimmed off, with burned out just being a term that became common in use.

..............Buckshot

[yodar]

Convince yourself -- Melt a pot of WW and let it just sit. Watch the dross under good light as it sits there and bakes -- it will turn a golden color. That gold is the tin coming out of solution. Tin is the only component of that alloy that is golden colored, both the lead and antimony are silver.

Make some Sweet-tea. How will you get SUGAR to come out of solution

In a solution the only way you can get a component to come out (precipitate it) it to change the solubility.

1.Reduce the amount of solvent the tin is dissolved in. You cant do that, tin is dispersed throughout the solution and travels with the lead. Lead, the solvent, has a vapor pressure far in excess of the heating capacity of your pot. Did you see the Lead BOIL? NO!

2 Reduce the solubility by lowering the temperature. We do that with copper by lowering the temperature below 700 d F but you cant do that with Tin. When tin's solubility curve is reached, the alloy has solidified.

3. Lower the atmospheric pressure. (SURE!)

You are not seeing TIN! You are seeing Refractive particles that may or may not be complexed with your flux. Tin cannot come out of solution. You are violating some laws of physics.

OH! Its Stannous OXIDE that's coming out of solution and floating to the top. SURE if you are running the pot at >1000 d F which is the oxidizing point of Tin. The Linotype-PRINTERS need to repopulate their pots with Tin-augmented metal 'cause they run their pots at that temperature to assure type-mold fill-lout and they do lose tin oxide in their slag..

Get real. The most likely basis for these particles filming on top of you alloy are flux-complexed contaminants.

I used to serve the quality control labs of Cerro Copper, St. Joe Lead and their successors.We talked about this meyht frequently. I am the son of a metallurgist who taught me casting who while I was a child he was at work making the mercury battery for the gummint at PR Mallory.

Investigating that issue years ago he took samples to the company GC and proved it was DIRT, flux, and not Tin.

Its DIRT face it! We all can produce an alloy with a little DIRT in it, especially if we start with wheel weights. Oxams' Razor

I have been casting with <1% tin augmented wheelweight alloys for years and NEVER had fill-out problems suggesting loss of tin.,

Stop trying to convert this ART to sorcery.

yodar

[45r]

I think your right yodar,when my pot gets low and before I put sprues,rejects,ingots,etc. in I turn the heat up all the way up to get it back to 750 to 800 before my molds cool off to much while I'm getting the sprues,rejects,etc on big spoons to place back in pot.sometimes the lead in pot turned a gold color from getting real hot and had a lot of dirty fuzzy crud piling up on top of it before I got ready to refill.I skim it off and put it on slag pile and it sure looks like dirt to me.I know it wasn;t tin because I don't put much tin in my pot.I flux my WW alot when melting down to ingots with wax and marvelux and get what looks to be clean ingots but I think there must still be more dirt and crud in there than I want,but to keeps things moving and skimming as soon as possible to get possible zinc out before it melts I accept the slight amount that might be in the ingots.I flux with sawdust,wax, and stir with wood sticks and scrape sides bottom and all that in my bottom pour and get nice shiney bullets but WW alloy still isn't as clean as hardball alloy I've tried from midway.I've fluxed and fluxed tring to get WW that clean but I think maybe WW might have to much dirt from miles of going down the road to get completely off.I learn a lot from these posts and do get fairly clean and shiney bullets but always looking for improvement if possible.I can tell that most of the casters here know a lot more than I do and I'm glad to able to learn from them.Sure beats learning the hard way and very interesting.

[w30wcf]

A number of years ago, using a 90/5/5 alloy I ran a short test to see if there was any loss of the components during casting. I started with a 10# pot full of alloy and started making bullets until I ran the pot dry (not a good practice unless you want to burn out your heating element prematurely) with no stiring / fluxing in between.

Result: The bullets weighed the same from start to finish. Had there been any loss of tin, the bullets made as the alloy was depleted would have weighed less. They didn't. :-D

w30wcf

[Ricochet]

One source states that pitch/ rosin (and probably fluxing paste) will reduce tin oxide starting at - believe it or not- about 450 degrees fahrenheit. FWIW
OK, thanks!

[LAH]

Stop trying to convert this ART to sorcery.

It's not art. It's uh.........uh...........uh..............well it's not art.

[leftiye]

FWIW

Oxides can form on metals BEFORE they melt. Blueing on steel is an oxide. I'm not talking about chemical blues, though they too are the same oxides, I'm referring to temperature blueing. Scale on steel is layers of oxide that have formed on hot (not melted steel). It sounds real probable that oxides of all the constituents of boolit alloy will form at any tempetature above molten.

What doesn't sound possible is that you can flux a metal which comes straight from the refiner/ manufacturer (and is as clean as it can be refined, and can be proven by analysis), and that the scum will disappear (which dirt doesn't do), and that the same scum will start forming again immediately. And that you can repeat the process ad infinitum, and that it will keep disappearing, and reforming immediately after fluxing. If it were dirt, as stated, it would not recombine. Nor would dirt continue to come out of wherever it might be hiding (dirt doesn't go into solution) indefinitely as that scum keeps re-appearing. There's no way THAT MUCH dirt could be in any of our metals.

Alternatively, skim it off, save the dross, until all of the melt is gone. Then flux the dross and see what happens ( bet you can't guess)!

[Bass Ackward]

Ain't it strange how we again get different results. Here are two examples.

I just tried to take a picture of bullets molded two months ago and it's too dark to show the difference clearly with my photography skills.

What I have is two batches of bullets. One batch was 35s molded from a bottom pour RCBS pot loaded with the only rifle mix I have, WW +2% tin. This was loaded fresh after my 20-1 pistol mix was emptied completely. These were molded at a measured 750 degrees until the pot was @ 90% empty.

At this point, I wanted to lay in some 311440 bullets before I sold the mold to a board member here, so the sprues and rejects were dropped back into the pot, the pot was then increased to 850 measured degrees, fluxed with no dross removed, and the bullets molded without adding any fresh to the melt or any more tin.

The temp was increased because this was a 6 cavity aluminum mold that needed to be filled out. And since I was selling the mold, I didn't want to smoke it for the next fella.

The result was an immediate and noticeable difference in the appearance of the two batches of bullets when laid them side by side. The first batch appeared as expected to have high tin content and shines like a mirror. The second batch appeared as expected, slightly grey with a dull shine as I would expect from lost tin. Same mix.

Today, the 35s still appear to shine have that high tin look with only slight dulling that immediately polishes up with one swipe of a paper towel. They measure 14 BHN.

But the 30s are dull and some even have some oxidation on the nose. They have a dull shine that won't polish up with even some effort with a cotton towel. And they are just a shade over 13 BHN.

Next, I have a 45 caliber, steel mold that when I mold at 750 degrees that I can produce shrunken band syndrome from tin and only tin mixes. The tin leaves the mix right in the short second or two of time it takes before solidification. Increase the percentage of tin and the shrinkage gets worse until it becomes a deformity. This effect can be minimized by cooling the mold, but my point is that without tin you will never see it.

I apparently am not the only one to observe this as Dan at Mountain Molds says his customers cry and complain about this effect often.

These are two different examples of separation or loss or what ever anyone wants to call it at casting situations. Bottom line, it's going to be hard to convince me that you can't separate or burn off tin at casting temperatures when I have experienced it all my life. So if I can get a brighter day, I will attempt another picture. You'll have to live with the 1000 words today.

[Lee]

Read this;

http://rds.yahoo.com/_ylt=A0geu8j46xpG5QQBtylXNyoA;_ylu=X3oDMTE4bnZvb3Z yBGNvbG8DZQRsA1dTMQRwb3MDMzkEc2VjA3NyBHZ0aWQDRjY1N F8xMTA-/SIG=13hbheggi/EXP=1176255864/**http://www.airproducts.com/NR/rdonlyres/7687522B-F373-4B12-8177-2BA1272DE890/0/tr_atmscmp.pdf

There's some very interesting statements in there. Written by some people who had better know what they are doin. Of course, that's just MHO, and what do I know??.........Lee:wink:

[3sixbits]

Make some Sweet-tea. How will you get SUGAR to come out of solution

In a solution the only way you can get a component to come out (precipitate it) it to change the solubility.

1.Reduce the amount of solvent the tin is dissolved in. You cant do that, tin is dispersed throughout the solution and travels with the lead. Lead, the solvent, has a vapor pressure far in excess of the heating capacity of your pot. Did you see the Lead BOIL? NO!

2 Reduce the solubility by lowering the temperature. We do that with copper by lowering the temperature below 700 d F but you cant do that with Tin. When tin's solubility curve is reached, the alloy has solidified.

3. Lower the atmospheric pressure. (SURE!)

You are not seeing TIN! You are seeing Refractive particles that may or may not be complexed with your flux. Tin cannot come out of solution. You are violating some laws of physics.

OH! Its Stannous OXIDE that's coming out of solution and floating to the top. SURE if you are running the pot at >1000 d F which is the oxidizing point of Tin. The Linotype-PRINTERS need to repopulate their pots with Tin-augmented metal 'cause they run their pots at that temperature to assure type-mold fill-lout and they do lose tin oxide in their slag..

Get real. The most likely basis for these particles filming on top of you alloy are flux-complexed contaminants.

I used to serve the quality control labs of Cerro Copper, St. Joe Lead and their successors.We talked about this myth frequently. I am the son of a metallurgist who taught me casting who while I was a child he was at work making the mercury battery for the gummint at PR Mallory.

Investigating that issue years ago he took samples to the company GC and proved it was DIRT, flux, and not Tin.

Its DIRT face it! We all can produce an alloy with a little DIRT in it, especially if we start with wheel weights. Occam's' Razor

I have been casting with <1% tin augmented wheelwright alloys for years and NEVER had fill-out problems suggesting loss of tin.,

Stop trying to convert this ART to sorcery.

yodar

This is the same information that I have found from textbooks on this subject. In the next few weeks (when things dry out around here) I will be reducing nearly 850 pounds of Linotype to ingots. four 22 gal drums of WW. Along with several thousand pounds of sheet lead. I will take three samples to Oxford Assaying and Refining Inc. in Anchorage to see what I've got to deal with. I will post the reports here for all to see. I figure I might get all the mileage I can for my money. I can take digital pictures of the reports and think this might be the easiest way to report.

[leftiye]

Both of you guys know what you know, and are studiously ignoring anything that doesn't support your pet theory, to include phenomena that everyone (yourselves included) sees anytime they're looking at a lead pot.

Tin (lead) oxides don't form below1100 degrees fahrenheit. Baloney, they form any time there is tin (Lead) and oxygen present. They accelerate in formation as temperature rises. Tin/ lead oxide vapors start to form according to this model, and there can't be vapors of anything that isn't present. I.E. if vapors are present so is the material (chemically identical) that the vapor was in before it became gaseous. At least according to the department of Chemistry at my local University. Any of us can and have read reference materials on Chemistry all of our lives whenever we needed information. How is it possible that metallurgy can supposedly supercede chemistry when metallurgy has at it's basis chemistry.

Oxides aren't present, AND oxides can't be reduced. Neither of you has gone beyond asserting these statements. You've made your assertions, and expect them to stand because you said them. WRONG. Especially when the least of us fools can see different.

Take your lead pot and enclose it in a glass box or other enclosure where you can see the melt. Fill the enclosure with Nitrogen, Carbon dioxide or other basically inert gas that will exclude oxygen. Have it so that you can flux the melt without losing the shielding gas if it is necessary to clean the surface after the metal becomes molten (this is when most oxides are formed). Fluxing shouldn't be necessary. Then tell me if "dirt" continues to form on the surface. Then tell me why oxygen is necessary before "dirt" will form.

[Dan308]

Check the cooled dross with a magnet. If it's tin the magnet will stick. Tin is highly magnetic.

[R.M.]

Dan
Tin is not magnetic. The only material that is is iron, and it's many alloys.

R.M.

[grumpy one]

R.M. - as a pedantic and useless intercession here, don't forget cobalt and various rare earths.

[13Echo]

Well, all this is very interesting so I went to the Lyman Cast Bullet Handbook. On page 48 under High Temperature Casting it states "at temperatures not exceeding 750deg F the oxidation of a small amount of tin in solution leads to the formation of a protective oxide barrier across the melt which retards further oxidation. ----- It is at its best when left undisturbed as when using a bottom pour pot." It goes on to state, "at higher temperatures, the protective mechanisim begins to break down by an as yet undefined mechanisim and drossing increases. Laboratory experiments have shown that perceptible drossing (what you can weigh, not just see) of undisturbed linotype melt begins at 842 deg F, while for Pb - 5% Sn melts the majority of tin is drossed off in as little as 30 minutes at 1050deg F. Translated into practical terms , this means composition control can be a real problem when casting hot for an hour or more."

So it seems tin is lost at high temperatures especially if the top is disturbed as by ladle casting or is not protected as with kitty litter. Lyman recommends sprinkling boric acid on the surface of the melt. This will form a glass like coating that is airtight. This would work well with a bottom pour pot but isn't much help for a ladle caster like me, so I cast at as low a temperature as I can (about 850deg F for the big 540gr projos for my Sharps) and flux frequently.

By the way, tin is not magnetic.

Jerry Liles

[Andy_P]

All the smilies we have and no "Eating Popcorn" and watching the show one! :) Knowledge is good, and I have seen some good theories and strong evidence.

I have made my decision and embraced the "Gospel of Oxides", or as some would say I "Drank the Oxide Koolaid", but the essential question is: "So what?". At the temperatures we smelt at, how much tin, lead and antimony is lost? Seems the answer is: "a bit, a bit less, and almost none". Since I add tin anyways, I am much more concerned about losing antimony, so I am careful to cull the pure lead stick-on weights, so as to not dilute the mix.

[leftiye]

Andy, For me, right now, the question is to try to get the oxides out of my melt so that they don't affect my boolit quality. And the stratagegy is to keep them from forming, and not put any into my pot. I think that actualy loss of tin (oxides are of all three metals) isn't to be really worried about at lower temps (I do all of my casting below 700 degrees).

[floodgate]

RM:

Another metal that shows ferromagnetism, though not so strongly as iron, is nickel. Not wholly off-topic, as Belding & Mull made moulds out of "pure" nickel for a couple of years back in the early 1920's. They cast very well, and do not rust or corrode, but were tough to machine and ended up costing twice what their iron moulds did to make.

The blocks are marked "NICKEL" (and the contemporary ones "IRON", as they were hard to tell apart by heft, color or feel); if anyone runs across one of these and is willing to part with it, let me know. It would be worth the price of a Group Buy - or maybe even two - to me, to compare with my iron B & M's.

And yes, they ARE moderately magnetic.

floodgate

[R.M.]

Now see, you're never too old to learn something new. :drinks:

[Buckshot]

............I did try some very high temp casting once using a recommended layer of molten Boric Acid as a barrier over the melt. It melts as a somewhat clear and thick (ie: syrupy) layer but does become less so as the temp raises. However it was a major PITA and I could see no benefit in my castings, other then it took a LONG time for the sprues to set up. One thing though was that there was no dross formed, but the mess made by the melted Boric Acid was such that I will just continue to flux as before and be done with it :-)

...............Buckshot

[montana_charlie]

I'm not saying the metal does not oxidize, I'm saying I can not see any. This may be because it is invisible in the air????
The man seems to have 'oxides' confused with 'vapors'.

Tin/ lead oxide vapors start to form according to this model, and there can't be vapors of anything that isn't present. I.E. if vapors are present so is the material (chemically identical) that the vapor was in before it became gaseous.
And, anyone looking at rust on cold iron knows he sees 'oxides', not vapors.

Its DIRT face it! We all can produce an alloy with a little DIRT in it, especially if we start with wheel weights. Oxams' Razor

I have been casting with <1% tin augmented wheelweight alloys for years and NEVER had fill-out problems suggesting loss of tin.,
We don't all start with wheelweights, and multiple melts of the same batch will eliminate any dirt that may be present. But the 'scum' will always return.

An observation...
If your tin percentage is less than 1%, I doubt would you ever know if some had been lost?

Andy, For me, right now, the question is to try to get the oxides out of my melt so that they don't affect my boolit quality.
I'd say your options are scoop 'em out, or stir 'em in.
If you bottom pour, you should just be able to let 'em lay on top till you're done.
CM

[leftiye]

Montana,
There seem to me to be impurities or oxides that get down to the bottom of a bottom pour and then into your boolits. I'm working on avoiding these by using a two pot system where all new melted material (including sprues and rejects) is fluxed previous to adding to the casting pot. The main pot is then fluxed, and covered (lid and floating oxygen seal layer of charcoal), and the process is repeated when the pot runs down. The melting pot is also partially covered leaving only a hole to add the various pieces in through. It's kept smoking with sawdust to exclude oxygen. Not quite good enough yet, but I'm working on it.

[montana_charlie]

Montana,
There seem to me to be impurities or oxides that get down to the bottom of a bottom pour and then into your boolits.
I kinda had you pegged as a bottom pour type...now it's proven.

I've never had any luck with that method, so I gave up on it.
I guess the advantage of the dipper is...you get to 'see your alloy' before you pick it up...so you can know that it's clean when it goes in the mould.
CM

[Sundogg1911]

just stir and remove the dross, you'll be fine. you're not going to scoop all of the tin off the top. I have noticed less variation in weight with fluxing, (but not very much at all) it could be metals slightly seperating, but I really think it's just from impuritys that i'm not fluxing to dross and scooping off the top.

[leftiye]

Monkey wrench. I just read lee's second article. Interesting thing, when two alloyed metals are heated, the most active one does most if not all of the oxidizing. When you think about it this becomes obvious. The most active metal grabs any oxygen that the other metal does fix away from it again (by virtue of being more active). So, what is the scum on top of the pot? BTW, this research on tin oxides was conducted at about the same temps we cast at.

[wiljen]

The most reactive metals are those that are the least electronegative.

This means as you go down and to the left on the periodic table you find the more reactive metals.

Sn and Sb are electopositive metals and are good reducing agents, that is they oxidize.
Pb is an electonegative metal and will actually oxidize more active metals.
Arsenic is electopositive but not nearly as strongly as Sn or Sb.

So in order of decreasing activity you should have Sn then Sb then As. That would suggest that Sn would oxidize preferentially.

In double checking my info, I also read that Oxides of the electronegative metals are very weak and can be decomposed by heat which would suggest that the process of smelting would reduce lead oxide without fluxing. The flux is needed for the electropositives that tend to oxidize.

[leftiye]

Wiljen

Wow! good stuff! So tin is just hanging in the wind in bullet alloy, so to speak? The tin must break the weak electrical bond with lead to become free to combine with oxygen and becomes relatively active at that point (as compared to the other metals present). And lead oxide is relatively fragile? And therefore it is almost only tin that will oxidize in this alloy, as it will steal oxygen from antimony and arsenical oxides, and lead is actually quite inactive, by comparison. Did I get it right?

[Lee]

Bingo! Bango! Bongo! You guys are getting it right! Now just don't lose sight of what you want to do;
Prevent, Eliminate oxidation in the 1st place.
Reduce and reintroduce these metal oxides as metals in the 2nd place.
Keep on casting the silver stream in the 3rd place.

Errrr....maybe I've got my priorities reversed!!:-D ........................Lee:wink:

[Lee]

BTW, for the ferromagnetics, and ferrimagnetics among us;

Get out the old microwave oven magnet and test some iron, steel, lead, tin, nickel, cobalt and others as you see fit. I believe you'll find the only one that sticks to a magnet w/o some "alchemy" is iron or steel. All others require some rather severe processing to attain their magnetic qualities. Period. 'Nuff said...
Definitions of ferromagnetic and ferrimagnetic, if this tired old mind remembers correctly, is whether the material can experience an attraction into or out of a particular magnetic field. Ah, heck, it's been too long. But w/o super glue, tin don't stick to a magnet...................Lee:wink:

[wiljen]

I wouldn't say "almost only Tin". I would say that Tin(Sn) being the most active will preferentially oxidize first, followed by any antimony(Sb) present, followed by what little Arsenic(As) is in the pot. One must consider that we have a limited supply of tin in the pot and an unlimited supply of Oxygen in the atmosphere (comparatively speaking). This means that if we allow the process of oxidation to continue unabated, it will eventually oxidize all the Tin and move on to the next metal in order of decreasing activity. You could, if done exactly wrong, end up with damn near pure lead by oxidizing all the active metals and removing them in the dross. The good news here is that Tin is the easiest to replace in an alloy (most readily purchased) and the fact that it and Antimony oxidize first helps us keep from loosing the Arsenic which is the most difficult element to obtain. This also confirms that my practice of adding a spool of 95%Sn / 5%Sb solder to each 100 lbs or so of WW I smelt is on target as it enriches the two things we are most likely to lose and in roughly the percentages of the two alloys that are being oxidized under normal smelting conditions.

[13Echo]

So solders used by plumbers today are leadless but contain antimony (Sb)? From what I've read antimony is about as toxic as arsenic. Is it just not bioavailable when used as a solder?

By the way, when I was a youngster there was enough nickel in a Canadian Nickel that it would be attracted to a magnet. The US Nickel had less and was not attracted. No alchemy was required, at least for nickel. I can't speak for cobalt or the rare earths.

Jerry Liles

[wiljen]

So solders used by plumbers today are leadless but contain antimony (Sb)? From what I've read antimony is about as toxic as arsenic. Is it just not bioavailable when used as a solder?

By the way, when I was a youngster there was enough nickel in a Canadian Nickel that it would be attracted to a magnet. The US Nickel had less and was not attracted. No alchemy was required, at least for nickel. I can't speak for cobalt or the rare earths.

Jerry Liles


Not all lead free solders contain antimony, I found a brand that does and stocked up.

[montana_charlie]

The good news here is that Tin is the easiest to replace in an alloy (most readily purchased).
Sorry, but I don't see that as good news.
Those of us buying (or carefully blending) a good old 20/1 or 30/1 alloy sees that tin as the most valuable...therefore the least readily replaced...metal.

A guy looking at 20 lbs. of WW alloy might have little or nothing invested, while a similar potful of 20/1 is worth (around) $47. And, $9 of that is the tin alone!
Add the fact that the tin is the only thing modifying the hardness of the alloy and you find it is 'irreplaceable' for two reasons...cost and alloy temper.

So, if you scoop out a couple of tablespoonsful of 'scum', you have changed the alloy composition by some unmeasurable amount. Meaning, what you so carefully blended (in the beginning) has been haphazardly modified by the time you're done. I find that as 'uncomfortable' to think about as a persistant oil leak.

Oil costs much more than gasoline, and your car carries a smaller amount of it than fuel. If there is a constant drip from your oilpan, your most valuable petroleum product is continually leaking out. You can shell out the money to keep replacing it...or find a way to prevent the loss.

That is the value of a fluxing method that blends (reduces) oxides back into the melt...and according to the most recent posts (above) it might be safe to assume that all of the oxides visible (in that 20/1 mix) are from tin.

If true, the question asked in the title of this thread can be answered by saying, "Losing tin in the dross is not a myth."
CM

[nighthunter]

My father, who taught me a lot about casting, learned a lot of his knowledge as a cable splicer for the telephone company years ago when they used lead for cable sheathing. He still laughs today about lead exposure and blood tests. This is a different story though. My father taught me to work the dross against the side of the meling pot with my dipper. This was before the development of bottom pour electric pots.Eventually the dross would dissapear and all that was left was the dirt that was contained in the dross. I believe that you can work these metals back into the melt. I am not a chemist. I don't know a whole hell of a lot about metalurgy. I just know that if you work the dross against the side of your melting pot the metal goes back into the melt. If I am wrong let me know. But I definately think that is better than skimming it off the surface and discarding it.
Nighthunter

[wiljen]

Sorry, but I don't see that as good news.
Those of us buying (or carefully blending) a good old 20/1 or 30/1 alloy sees that tin as the most valuable...therefore the least readily replaced...metal.


I meant it as good news only in the sense that elemental antimony is very difficult to add to alloy, and elemental arsenic is difficult to obtain and work with.

I certainly am not suggesting that you shouldn't flux and reclaim all the tin that you can.

The next question becomes would the shooter know the difference in 20:1 and 19.75:1? 19.85:1 ? I think we do lose some small amount in the dross regardless of our best fluxes. At what point does that become noticeable?

Wiljen

[Bass Ackward]

The next question becomes would the shooter know the difference in 20:1 and 19.75:1? 19.85:1 ? I think we do lose some small amount in the dross regardless of our best fluxes. At what point does that become noticeable? Wiljen


Wiljen,

You can be casting at 750 degrees with 20-1 using a large caliber, steel mold that is holding the heat and pour a bullet have and have what is known as SBS or shrunken band syndrom. The appearance will begin as a localized frosty look and move to looking like grains of sand. That is where the bands fail to fill out completely at that point because you lost tin right in the mold. This doesn't happen with non tin mixes.

That's how fast you can notice.

[hivoltfl]

Very interesting thread and looks like lots of research has gone into most of the replies, The man that got me started in the silver stream taught me to watch the top of the alloy, shiney and looks like quick silver its right, off color or looks wrinkled or tan on top, dont skim it off, thats the sign that you are gonna have to flux soon.
That was 42 years ago and I still follow that practice.

Rick

[sundog]

Ya know, whatever is in the dross doesn't make much difference. Anything I skim goes into a recycle can and that gets thrown in the next big rendering batch. Whatever floats out then gets trashed.

I weigh my match boolits to cull the light weights. I don't see much variation. A true light weight, for what ever reason, is indication of a flyer. I don't pay too much attention to how much of this, and how much of that makes the alloy. What I want is a long run of the samest stuff. Now, if it's for a very specific application, then yes, watch what you got. BUT, here at home, beyond a hardness tester (which I have not) and a scale, there's not much else to really tell.

[wiljen]

Wiljen,

You can be casting at 750 degrees with 20-1 using a large caliber, steel mold that is holding the heat and pour a bullet have and have what is known as SBS or shrunken band syndrom. The appearance will begin as a localized frosty look and move to looking like grains of sand. That is where the bands fail to fill out completely at that point because you lost tin right in the mold. This doesn't happen with non tin mixes.

That's how fast you can notice.

Ok, I'm lost. If it happens with 20:1 is the implication that the particular bullet was poured from a non-homogeneous mix of materials that has less tin and thus suffers SBS? I don't see how this shows that you can tell the difference between 20:1 and 20:0.95.

[yodar]

TIN AND LEAD don't separate out of our melts. Components of a solution remain in solution

TIN has a vapor pressure requiring 1100 dF or so to EVAPORATE. TIN oxidizes at a temperature far higher than our pots can supply unless you leave the alloy under heat for a long time.. Linotype machines are the only casting operations that require augmentation of their alloys with tin rich metals,and that takes days and days of contant heat before that augmentation is needed..

You gold film seers are merely seeing a change in the refractive index of the surface of the metal along with stuff complexed with your flux. I am the son of a chemist who taught ME casting and he took a sample of golden film to the analytical chem lab when I was a kid and did a WET CHEM-ANAL on it. They didnt HAVE G.C.'s then. It wasnt tin, OR LEAD.

IT WAS LEAD/TIN/ANTIMONY ALLOY AND DIRT

You can NOT return STANNOUS OXIDE (or lead oxide) to the reduced state unless to have some exotic chemicals and high heats. In my duty in supplying the met labs in my territory, which included Taracorp, St. Joe Lead (Fluor) I discussed these issues as they received my metallurgical microscopes for service. The explained it to me, and even tho I took Biochem, and not general Inorganic, I understaood from the guys that know that this hoo haw about tin being lost is a way to sell flux and sorcery. You have to heat the SNOT out of your pot for an extended time to oxidize the components.

Fluxing DOES NOT remove oxides from dross. It is a SURFACTANT to accelerate the
dissociation of UNDISSOLVED substances from the mix, as a surfactant promotes particle aggregation to the surface for removal.

Like I said, Lead Oxide and Stannous Oxide are VERY resistant to chemical reaction. OXIDES are some of nature's most stable compounds. Why do they make paint pigments out of them? Is it LIKEly a sprinkling of Marvelux would convert Tin Oxide to elemental tin ? IMPOSSIBLE. The guys at St. Joe lead explained they preferred to smelt sulfides of lead rather than OXIDES. To reduce oxides of lead (or tin) requires a reducing atmosphere, FREE of ANY oxygen, too sexy and expensive reagents, and some temperatures we cant achieve.

A metallurgist on another list explained the refractive index thing based on localized cooling and crystallization of the surface melt having a different refractive index, thats why it is gold.

Stop fightin the laws of physics , stop the witchcraft, and get down to some serious disciplined casting

yodar

[3sixbits]

yodar: Sir I feel at this point it is useless to bring in logic to these discussions, about the time you think it's getting across, up jumps the soothsayers and you go back to square one. Is it any wonder people still follow mirages across the desert? Once again you have not posted anything but the truth. That the turth you posted will be denied, you can take to the bank!

[Bass Ackward]

Ok, I'm lost. If it happens with 20:1 is the implication that the particular bullet was poured from a non-homogeneous mix of materials that has less tin and thus suffers SBS? I don't see how this shows that you can tell the difference between 20:1 and 20:0.95.


wiljen,

You are not lost. The answer to your question was that you can't tell minute change. The point it becomes noticeable is when you drop hardness. Since lead tin mixes can be measured immediately after casting, you don't have the disadvantage of antimony mixes where you have to wait two weeks for the result. 20-1 is 10 BHN on my tester and I just keep it there.

I wanted to show that there was another question to be asking about tin burn off. Nobody seems to ever ask why I frosty bullet got frosty. And why a frosty bullet can get undersized and on and on.

[wiljen]

wiljen,

You are not lost. The answer to your question was that you can't tell minute change. The point it becomes noticeable is when you drop hardness. Since lead tin mixes can be measured immediately after casting, you don't have the disadvantage of antimony mixes where you have to wait two weeks for the result. 20-1 is 10 BHN on my tester and I just keep it there.

I wanted to show that there was another question to be asking about tin burn off. Nobody seems to ever ask why I frosty bullet got frosty. And why a frosty bullet can get undersized and on and on.

Thanks for the clarification, I was trying to make the leap and couldn't make it fit. Now I see what you were suggesting. If the same pot of alloy does produce some bullets with SBS and others without, assuming yodar is correct, we must assume it is caused by temperature variation of either the melt or the mold. I say this as a true solution is homogeneous and as he suggested the elemental composition can't be changing under the conditions we produce. That leaves the only thing within our control/sphere of influence being Temp of the melt, the mold, or both.

[montana_charlie]

yodar and 3sixbits,
Do either of you guys use flux? If so, for what purpose?
CM

[3sixbits]

Yes, I flux to condition the alloy. I use sawdust and or sodium hydroxide. When the alloy metal is brought to the correct temp to clean and remove what may be copper in the mix, I stir in sawdust first, and I do mean stir for several minutes, this brings all the dross and hopefully any cooper that maybe in the alloy, will be in the dross. The dross by the way (and not to belabor the point) is a hazmat material and must be disposed of properly. The best way to get rid of the dross is to sell it to a scrap metal dealer or refinery. Why would they want it? Because they can recover these oxides back to the parent metal. It has value! Not much, unless you have tonnage. THIS DROSS CAN NOT BE RECOVERED BY FLUXING, IT CAN ONLY BE REMOVED BY FLUXING!!!

[montana_charlie]

Yes, I flux to condition the alloy.
There is that term you would define for us, before.
What is the source of your alloy, and what elements do you believe to be in it to start with?
Are those elements changed in any way by 'conditioning', or does the removal of dross constitute bringing the entire alloy to a new 'condition'?

When the alloy metal is brought to the correct temp to clean and remove what may be copper in the mix,
What is the 'correct' temperature for copper removal?

I stir in sawdust first, and I do mean stir for several minutes, this brings all the dross and hopefully any cooper that maybe in the alloy, will be in the dross.
After you have finished this procedure, or perhaps have done it more than once to the same quantity of alloy, do you feel there is no more dross in the pot?

THIS DROSS CAN NOT BE RECOVERED BY FLUXING, IT CAN ONLY BE REMOVED BY FLUXING!!!
After you have removed it, does no layer of grainy grey matter ever accumulate on top of your alloy...increasing in thickness as time goes by?

If it does...what do you call it?
CM

[Lloyd Smale]

Im no scientist and have no scientific terms to quote but i do have some real world testing results. About 3 years ago i did a test over a one month period casting 10 differnt molds. I was casting with a 10 lb lyman pot. Each day i would start with a full pot and cast two molds until the pot was empty. First pot of the day id flux every 15 minutes second pot id not flux at all not even at the start. Id then weight sort the bullets in groups from the heaviest to the lightest and figured extreem spread and average spread. Over that month i came up with this my extream spread averaged 4 percent more with the fluxed lead and my average spread was 3 percent more with fluxed lead. In all actuallity not enough with either to loose sleep over but if im loosing tin while i cast (which i doubt) it sure didnt show up in the results. Needless to say i dont flux anymore except when smelting. Alloy was #2 and the flux was a comecial blue wax like flux i got from a lineotype printer.

[felix]

Flux might or might not cause air bubbles. Depends on the stir quantity and quality. Different air bubbles might be in the alloy from one stir to the next. So, is it the flux? Or is it the stir? ... felix

[Lloyd Smale]

no clue felix i never took it any farther. I guess i just figured that it didnt do much for me and why waste the time. If it effected my bullets id flux every 2 minutes if it would help. Im sure it would take alot more scientific and controled test then what I did as results would probably vary with every alloy and every different type of flux a guy used and how it was used. But there surely is no big giant benifit to doing it either way and in my opinion for what its worth, in normal casting if a guy is loosing tin and antimony it sure isnt enough to loose sleep over. But in my case you have to keep in mind that my casting is for handguns not precision long range rifles.
Flux might or might not cause air bubbles. Depends on the stir quantity and quality. Different air bubbles might be in the alloy from one stir to the next. So, is it the flux? Or is it the stir? ... felix

[Lloyd Smale]

ps-- It was after this test and using the bullets i casted taking matched weights and the widest spread weights and shooting them that I also came to the conclusion that at least for handguns bullet weighting and sorting is also a waste of time as i couldnt measure any appreciable differnce in the way any of them shot.

[LAH]

ps-- It was after this test and using the bullets i casted taking matched weights and the widest spread weights and shooting them that I also came to the conclusion that at least for handguns bullet weighting and sorting is also a waste of time as i couldnt measure any appreciable differnce in the way any of them shot.


Creeker says: AMEN

[yodar]

It seems nonsense that tin will come out of your wheelweight solution if you don't flux, or you skim off the dross with too much vigor. Is the tin not bound with the antimony and lead in solution? How then can it just float to the surface?

Isn't the "shiny stuff" that's attached to the metal parts that are skimmed off lead/tin/antimony, and not just tin?

Antimonial-tin zinc complexing occurs ONLY at crystallization and the intermetallic complex formation takes time to develop

Nontheless, if tin is dissolved, or anything ELSE dissolved, it will rtain it's solute percentage relationship as long as the solution exists. It is taught in physical properties of matter class that it takes a lot of WORK to seperate elements of a solution

[3sixbits]

There is that term you would define for us, before.
What is the source of your alloy, and what elements do you believe to be in it to start with?
Are those elements changed in any way by 'conditioning', or does the removal of dross constitute bringing the entire alloy to a new 'condition'?

What is the 'correct' temperature for copper removal?

After you have finished this procedure, or perhaps have done it more than once to the same quantity of alloy, do you feel there is no more dross in the pot?

After you have removed it, does no layer of grainy grey matter ever accumulate on top of your alloy...increasing in thickness as time goes by?

If it does...what do you call it?
CM
I have unlimited access to sheet lead, once this material is removed from buildings it is considered a hazmat and is given to me by various contractors. I'm running out of room for it. There are four types of sheet lead. Chemical @ 99.945 Pb, 0.05 Cu. 4% sheet is composed of 4.00 Sb, 0.05 As, 0.04 Cu, 95.91. 6% sheet contains 6.25 Sb, 0.10 As, 0.04 Cu and 93.607 Pb. And last (and pray you never get any of this) Strontium, which contains 0.90 Sn, 0.15 Sr, 0.02 Al, 98.927 Pb. If you think zinc is bad, just wait till you run into this crap. The Al and the Sr just does everything you can imagine to resist casting.

Next I use WW, just like most of us. I have not had any problems finding them in large quantities yet and always for free.
Linotype: the vast majority of what is called Linotype is the eutectic varity (not all) which is 12.00 Sb, 4.00 Sb, 0.08 As, 0.08Cu, 83.84 Pb. There are many other types that I buy in this category but refuse to talk about, as they are not considered by bullet casters to be any good. I do not think that they understand the problems with these other type, is they all contain a lot of Cu. Just like babbitt metal.
Conditioning: means to make the alloy usable for the intended purpose. Remember, we bullet casters are not the only ones that have a use for these alloys, So conditioning can only be defined as above. There is various way to condition the alloy for the many different purposes that the alloy will be used in. But for our purpose we want metal that will first of all be easy to cast. Second, not contain any tramp metal, Cu, Al, Zn and the oxides of any other metal . I do not feel it is necessary to get into what happens when we have the presence of these elements in our melt.
The best way to remove tramp (for us) is by keeping the temp of the melt to liquidus and stir in sawdust and I mean stir the heck out of the melt. Then to bring the temp up and remove the dross and the tramp Cu. Now is the time to make the decision on whether you need to go on with the fluxing or not.

[Lee]

Ummmmm, just asking, but if you've got "lead" sheet out the wazoo, running out of space to store it, got any for sale?? "Vintage" lead on e-bay??? Lots of us would (might??) be willing to take it offn your hands, unless the shipping cost is worse than gold???.
Even as a free auction, pay only postage, profits go to benefit the site??,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Lee

[3sixbits]

I wish it was that easy to recover the lead from the sheets. It still has to be processed from the sheet. It always has paper and glue stuck to the surface. It has to be smelted, cleaned and cast into ingots. The shipping would cost the flat rate to your postal addy or who ever won the auction. If it is 6% sheet this means the addition of only 2% Sn to have prime bullet metal(6-2-92). Talk about cheap per hundred weight. It would not get any better for that kind of cost. Price of two pounds of Sn into 98 pounds of 6% sheet lead. But like you say the cost of shipping, However I do know that it cost the same to ship a pound gold as it costs to ship a pound of "sh_t".

[montana_charlie]

Well, 3sixbits, I asked you four questions and you answered two. This statement...
The best way to remove tramp (for us) is by keeping the temp of the melt to liquidus and stir in sawdust and I mean stir the heck out of the melt. Then to bring the temp up and remove the dross and the tramp Cu. ...came close to answering the third, but didn't quite get there.

The fourth is still dangling, and now I have another...
If you 'stirred the heck out of it' without using sawdust...how would things be different?

Your answer to this one will give us an idea of what you believe the sawdust is actually doing...
CM

[3sixbits]

Sorry about not giving you all you needed, my time was limited. I would have no way of knowing if any more dross has formed as soon as the cleaning is complete, I start casting ingots. I then start a melt of a trial alloy to see how it casts, what the target weight and as cast size of the alloy. I do this in a small pot I have for this purpose. No I never see any further dross after cleaning or alloying. The reason is that I can't see the surface of the metal, It's covered in powdered charcoal. When I do my bulk alloying after I'm sure of no problems and I have a pretty good idea of what I've got, I go to my big pot (about 7 and a half gallons) and alloy and cast into ingots. The pot I cast bullets from is a 40 pounder and gets the charcoal cover. The saw dust is cleaning the metal and frees up dirt and oxides. This lets us remove the problem that would interfere with are bullet making. Sorry I don't have more time.

[montana_charlie]

Ok, 3sixbits, if I understand correctly...this is a summary of your beliefs.

1. Sawdust is a suitable flux for 'conditioning' the alloy, meaning that it cleans the metal, allowing the dirt and oxides to separate.

2. Dirt and oxides rise to the surface of the alloy where the (visible) dirt is scraped off and the (invisible) oxides are ignored.

3. You don't believe that any more dross forms in your alloy, no matter how many times you might re-melt it for various purposes. But, even if dross does form, you will never see it because your alloy is always covered with powdered charcoal when remelted subsequent to the initial smelting operation.

Applying your beliefs to my casting bench...

- You have no experience with (and nothing to say about) the 'scum' that I see on my alloy...perhaps because yours (if present) is hidden by charcoal.
- No matter how many times I might have cleaned the alloy, you still feel that my 'scum' is primarily dirt.
- My 'scum', no matter how thickly it might accumulate, cannot be oxidized lead or tin because oxidization can only occur at extreme temperatures...and they are invisible, anyway.

Has this humble student listened correctly and now knows the truth?

Answer when convenient, but only if it's not an imposition...
CM

[leftiye]

yodar: Sir I feel at this point it is useless to bring in logic to these discussions, about the time you think it's getting across, up jumps the soothsayers and you go back to square one. Is it any wonder people still follow mirages across the desert? Once again you have not posted anything but the truth. That the turth you posted will be denied, you can take to the bank!

From one "sooth sayer" to one who is totally blind then, You may be right as to useless. I'm not so sure that you percieve even in any small degree where the problem lies though. Montana_charlie has been more patient with you than I am able to be. I've argued with you, cited scientific theory, and proof and you've totally ignored the obvious all through this thread. Beyond that the two of you haven't answered more than a question or two of all of those asked of you, nor have you cited any source, nor principle, nor anything else in support of your theories. FWIW, from my position your assertions violate numerous principles that I and others have put before you. AND you just ignore what is said and reiterate your "revelations." Yep, not only useless but also a waste of time! OH! Excuse me - just what logic was that? To involve logic you have to do more than just make the initial statement.

[montana_charlie]

TIN oxidizes at a temperature far higher than our pots can supply
You seem to prefer 'science' to 'experience', yodar. I'm not a scientific guy, but I can spell Google.
I invite you to chew on these...

Although these excerpts from published papers do not describe the tested alloys in a way that a bullet caster would recognize, it still seems they contain nothing but lead and tin.
BTW, 90(C) equals 194(F)...which is easily reached by MY pot.

Author(s):
R. A. Konetzki, Y. A. Chang

The oxidation behavior of a Pb-2.9 at.% Sn alloy was studied using Auger electron spectroscopy (AES) combined with sputter depth profiling. Samples were oxidized in air at temperatures less than 90 °C and at low oxygen pressures at room temperature. The oxide formed on the alloy after oxidation in air has an “oxide inversion layer,” where the amount of preferentially oxidized tin increases with depth into the sample, reaches a maximum, and then decreases to its bulk value. Internal oxidation of tin was also observed in this alloy, probably occurring along grain boundaries. Low pressure oxidation studies indicate that grain boundaries play an important role in the initial development of the oxide.

This excerpt (from a different article) seems to be even more clear that a lead/tin alloy will oxidize at non-extreme temperatures...and that tin oxidizes more readily that lead.

Oxidation Study of Pure Tin and Its Alloys via Electrochemical
Reduction Analysis
SUNGIL CHO,1,3 JIN YU,1 SUNG K. KANG,2 and DA-YUAN SHIH2
1.—Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejon 305-701, Republic of Korea. 2.—IBM, T. J. Watson Research Center,
Yorktown Heights, NY 10598. 3.—E-mail: sicho@kaist.ac.kr

The oxidation of pure Sn and high Pb-Sn alloys was investigated under different oxidizing conditions of temperature and humidity. Both the chemical nature and the amount of oxides were characterized using electrochemical reduction analysis by measuring the electrolytic reduction potential and total transferred electrical charges. For pure tin, SnO grew faster under humid conditions than in dry air. A very thin (10 Å) layer of SnO2 was formed on the top surface under humid conditions. The mixture of SnO and SnO2 was found for oxidation at 150°C. For oxidation of high Pb-Sn alloys, tin was preferentially oxidized on the surface, and tin content over the solubility limit suppressed the formation of lead oxide.

After a few paragraphs, the article continues with...

Considering Gibbs free energies in Table I, the formation of tin oxides is thermodynamically favored in the Sn-Pb system so that it is expected that tin oxide would be formed preferentially. Tin hydroxides, Sn(OH)2 and Sn(OH)4, can also form preferentially based on the Gibbs9 free energy consideration, but the hydroxides are unstable with respect to the corresponding oxides and would not form under ambient conditions or may undergo dehydration. Preferential oxidation of tin in the Sn-Pb system has been reported. Bird10 and Farrell11 have found that surface enrichment of tin in lead-tin alloy using x-ray photoelectron spectroscopy (XPS). Konetzki and Chang12 found that tin was preferentially oxidized on the surface of Sn-Pb alloys containing only 2.9at%Sn. Bevolo et al.13 and Shah and Eurof Davies14 showed that SnO2 was enriched at the outer surface and the surface was completely covered with a SnO2 layer in the laboratory environment. High-lead alloy such as Pb-3at.%Sn has been shown to exhibit surface segregation of tin, especially in the presence of oxygen. Tin was found to be highly segregated around grain boundaries. The rate of surface segregation of tin was considerably enhanced by exposing the clean surface to oxygen, which indicates that the oxidation of tin could be the driving force of tin diffusion to the surface along grain boundaries.

The two temperatures mentioned in this article convert to 302° and 698° Farenheit.

3sixbits might be taking note of the (apparent) fact that the oxides in question were visible enough to be analysed.

If these temperatures are "far higher" than your pot can supply, yodar, maybe that explains why your beliefs on this subject are so different from ours...
CM

[Lloyd Smale]

Hell you guys need to shut off your computers and go cast bullets. Quit worrying about the scientific mumble jumble. If you have 3 percent tin in you alloy and even loose 25 percent of it it woundnt effect your casting to any degree anyway. At least not that its going to show up on any target or animal.

[3sixbits]

From one "sooth sayer" to one who is totally blind then, You may be right as to useless. I'm not so sure that you percieve even in any small degree where the problem lies though. Montana_charlie has been more patient with you than I am able to be. I've argued with you, cited scientific theory, and proof and you've totally ignored the obvious all through this thread. Beyond that the two of you haven't answered more than a question or two of all of those asked of you, nor have you cited any source, nor principle, nor anything else in support of your theories. FWIW, from my position your assertions violate numerous principles that I and others have put before you. AND you just ignore what is said and reiterate your "revelations." Yep, not only useless but also a waste of time! OH! Excuse me - just what logic was that? To involve logic you have to do more than just make the initial statement.
Yea you guys are right, I was only kidding. Is it any wonder why some people grow to hate the internet? I think you two people have led me to that point. Any post addressed to me from either of you two will be ignored, is there an ignore feature on this web page, moderator?

[leftiye]

Cool with me! As stated you're already doing that.

[leftiye]

Montana C Out Flaming Standing! Yeah, I can tell you're a sharpshooter, and an elegant one too. Your post nails the central issue real good. If tin oxidizes when in solution at 300 degrees, and up, this discussion is over! I posted it a couple of times here, though not as clearly. From one soothsayer to another, let me buy you a beer!

[felix]

Moral of the story, folks, is to flux up front, and then don't flux again until the pot is empty. And, cover the pot to slow down any oxygen (21 percent in air), and please don't throw back the sprues until you are done casting for the day, or until the pot needs refilling for a re-run. A 20 pound pot is all I can muster up for a day's work anyway. The only exception to this rule about re-mixing is when you are intentionally using copper for a tougher boolit. Then you should mix every 10 cast cycles. ... felix

[tom barthel]

Believe what you wish. Take the advice that seems reasonable to you. Reject the rest. It's not worth arguing about. If it goes bang, I'm happy.

[cbrick]

felix nailed it, I flux at the beginning of a casting session, never during. Once I start casting nothing goes back into the pot, not rejects, sprues, additional alloy, the stirring spoon, nothing. This and a great deal more is practiced in the metals industry, it's called caring for and maintaining your alloy and they do it religiously and for a reason.

I find it a bit surprising how some in this thread have completely ignored Glen's post on the first page. Glen is a Ph.D. chemist involved in the environmental chemistry of heavy metals. Every single metallurgical report I have ever read, including Glen's, says that tin does oxidize out of lead alloys at normal casting temps when in the presence of oxygen.

One poster said that if it goes bang he's happy so it doesn't matter. If that is your goal then he is the most accurate poster in this thread.

Most of my casting and loading is for the highest practical velocity and accuracy in long range handgun and variations in the alloy and alloy BHN does matter. If you heat treat your bullets, the percentage of tin in the alloy will in part determine the final BHN. If you vary the tin percentage from batch to batch you'll never have bullets of consistent BHN. My long range testing has proven (to me anyway) that varying the BHN has a huge effect on groups.

Rick

[sundog]

Well, I've been casting for alot of years, and it looks like I'm gonna have to start over according to what y'all are saying. Naw. I normally put a bit of wood ash on the melt after a good flux, let it sit for a bit while the mould is preheating, run a few cycles to get acceptable boolits, and then everytime I'm waiting on the puddle to set up, I put the previous sprue back in the pot. I've been doing it for years when ladle pouring. My boolits are good enough that I suspect I will not change my procedure. Even on a long run the first and last boolits are well filled and within my acceptable weight spread. That tells me that whtever the alloy is isn't changing much - at least not enough to be decernable without assay. There's too many other variables at play beyond this that affect accuracy to worry over what's going on with percentages in the alloy. In the first place adding tin to WWs gives you tin in your WWs. That's all it is, tin in your WWs. And if the boolit don't fit, well, it doesn't make any difference what's in it.

edit - I forgot to mention. If I were shooting BR for record and money, I might change things a little. But, I don't even own a BR gun.

[felix]

Yeah, I think, no proof, that ladle casting more evenly distributes any air bubbles, and gives a better hole through the melt, via mold tilting, for the air bubbles to escape. Games can be played when bottom pouring to accomplish the same thing, but the same effect never happens often enough in practice. Bottom pour works good enough for small diameter boolits because the boolits are small enough in diameter to keep the edges of the boolit closer to the center line which keeps the dynamic inertia of the object on the lower side. 22s seems to maintain accuracy at a higher rpm, for example, than 45s because of this inertia. This is not 100 percent conclusive about accuracy, however, because 22s don't recoil like the 45s at the same velocity. More recoil, more errors, so no real proof of anything when realistically shooting. ... felix

[Lloyd Smale]

Rick i do a hell of a lot of long range shooting with sixguns and i agree. Change the alloy and you change everything. That just doesnt apply to long range either. Changing alloys will usually completely change the way a gun groups at 25 yards too. As much so as swapping primers or powders but what i dont agree to is that you can possilby loose enough tin while casting out a 20 lb pot to ammount to any real change in the alloy. Ive weighted enough bullets to know better. The same guys that preach this will water drop bullets and just the fact that bullets are dropping out of a mold at differnt tempertures each time varys hardness alot more then any amount of tin being lost in any melt. Tin does very little to harden lead what it does do is make your mold fill out better. Loosing a minute amount of tin by oxidation surely isnt going to effect your bullets to any measurable degree. Your dealing with a material makes up about 2 percent of your alloy and if you lost 2 percent of that 2 percent due to oxidation i cant see where that is going to cause a problem and i surely know you arent loosing half the tin in your pot due to oxidation.
felix nailed it, I flux at the beginning of a casting session, never during. Once I start casting nothing goes back into the pot, not rejects, sprues, additional alloy, the stirring spoon, nothing. This and a great deal more is practiced in the metals industry, it's called caring for and maintaining your alloy and they do it religiously and for a reason.

I find it a bit surprising how some in this thread have completely ignored Glen's post on the first page. Glen is a Ph.D. chemist involved in the environmental chemistry of heavy metals. Every single metallurgical report I have ever read, including Glen's, says that tin does oxidize out of lead alloys at normal casting temps when in the presence of oxygen.

One poster said that if it goes bang he's happy so it doesn't matter. If that is your goal then he is the most accurate poster in this thread.

Most of my casting and loading is for the highest practical velocity and accuracy in long range handgun and variations in the alloy and alloy BHN does matter. If you heat treat your bullets, the percentage of tin in the alloy will in part determine the final BHN. If you vary the tin percentage from batch to batch you'll never have bullets of consistent BHN. My long range testing has proven (to me anyway) that varying the BHN has a huge effect on groups.

Rick

[montana_charlie]

Tin does very little to harden lead what it does do is make your mold fill out better. Loosing a minute amount of tin by oxidation surely isnt going to effect your bullets to any measurable degree. Your dealing with a material makes up about 2 percent of your alloy and if you lost 2 percent of that 2 percent due to oxidation i cant see where that is going to cause a problem and i surely know you arent loosing half the tin in your pot due to oxidation.
Lloyd,
What you say is pretty logical if a guy:
- Primarily uses wheelweights (may add some tin)
- Depends on things other than tin to create 'hardness'
- Pours from the bottom spout
- Covers the alloy with something to exclude air
- Casts enough bullets in a single session to drain his pot
- Considers a 3-inch, 50 yard group as 'good shootin' from his rifle

I have more interest in the 'tin loss theory' because I:
- Take care to mix pure lead and tin in an exact ratio
- Tin is the only factor used for establishing bullet 'hardness'
- Cast with a dipper (alloy sees a lot of 'activity' and 'oxidation')
- Cannot cover the surface with an airtight layer
- Frequently cast only half of a potful, and need the remaining alloy to be as similar to it's original state as possible when I add more, next time
- Consider a 2-inch, 100 yard group as a sign that something needs to be 'fixed'

The differences in our methods...and goals...make the difference in our estimation of 'how important' this question is.


I find it a bit surprising how some in this thread have completely ignored Glen's post on the first page. Glen is a Ph.D. chemist involved in the environmental chemistry of heavy metals. Every single metallurgical report I have ever read, including Glen's, says that tin does oxidize out of lead alloys at normal casting temps when in the presence of oxygen.

Rick,
I didn't ignore his comment. I read it and agreed with it...then read the equally scientific(?) input from 3sixbits and yodar.
The contradictions were too antipodal for me to stay silent.
CM

[Lloyd Smale]

Id still like to see you actually test (if you havent allready) bullets using your method and then compare them to bullets out of the same alloy without worrying about it. Ive got a 3030 marlin and a 356 win. that with a scope on them will shoot groups hovering around an inch at 100 yards using cast and casted out of my pot that is never fluxed. I would guess a .10 of a grain of powder would make about as much differnce as loosing that tiny amount of tin and its pretty hard to control powder that accurately either. You have to keep in mind that if your loosing tin due to oxidation its an allmost unmeasureable ammount. I know it sure doesnt show up in weighting bullets. It doesnt show up on a hardness tester. So i have a problem buying that it will show up on a target. Im not here to get into a pissing match. Thats the farthest thing from my mind. But ive yet to see anyone document that it actually effected the accuracy of a gun. I have proved to myself it sure doesnt effect handgun accuracy at any reasonalbe range (or unreasonable) but i know rifles are a different animal and im surely not trying to say im an expert in that field. Id like to see someone shoot 10 5 shot groups using both methods in a proven gun with the same alloy and see if it actually effected groups. Because i seriously doubt it would and if thats the case this whole argument is a waste of time because were casters and shooters not scentists

[Bass Ackward]

Good points MC.

Lloyd,

Read my post # 31. It does show up with a hardness tester. That's the same pot just recycled one time. Mix temperature has a lot to do with it. So I guess you could say caliber and mold material play a part too since you may have to vary temp for that reason.

[montana_charlie]

Id still like to see you actually test (if you havent allready) bullets using your method and then compare them to bullets out of the same alloy without worrying about it.
Id like to see someone shoot 10 5 shot groups using both methods in a proven gun with the same alloy and see if it actually effected groups.
You're on, Lloyd. I'll put it on my 'to do' list so I don't forget it...but it may be some time before I get around to it.

For 10 5-shot groups, it will take four pounds of 'good alloy' allowed to oxidize freely...and four pounds (for the 'perfect bullets') cast with careful fluxing. Another four pounds (of each) will be needed just to keep the pot full enough to dip from, but at least the eight pounds used for the 'good bullets' will be kept in good shape. It will be the other eight pounds which will be (sorta) 'wasted'.

It will take some browbeating of my Scottish nature to make me actually do it...

You have to keep in mind that if your loosing tin due to oxidation its an allmost unmeasureable ammount. I know it sure doesnt show up in weighting bullets. It doesnt show up on a hardness tester. So i have a problem buying that it will show up on a target.
I understand your hesitance to 'buy it', Lloyd. By way of explanation (in the absence of test results) I submit this...

If I start out with some good 20/1 alloy (95/5 lead/tin) and only lose enough tin to equal 1.7% of the entire mass of alloy...I have dropped from 20/1 alloy down to 30/1 alloy. BPCR shooters will (for whatever reason) choose between these ratios when buying (or mixing) their alloy for casting.

Some will find (or feel) that 30/1 causes nose slumping, while 20/1 doesn't...or they may believe the softer alloy (30/1) 'bumps up' better in their gun.

I don't see bullet weight variation as much of a factor, here. As long as they meet a minimum standard which precludes voids, I really don't care 'how much' they weigh. I just weight match them to each other, to be fired in the same group.
I am much more picky about appearance, than weight.

It's also a fact that the two alloys are supposed to have different BHN numbers, '9' for 30/1 and '10' for 20/1. That has an effect on what the BPCR shooter believes about barrel leading control.

Now, I don't have any actual figures for this next statement, because I never weighed it, but...
I'm guessing that the amount of 'scum' (dross) I would skim out of my pot...just keeping the surface clear enough to dip clean lead...would amount to 3+ ounces from a totally emptied 20 pound pot.
That is up near the 1% mark, and I think I'm underestimating how much I would get. If most of that 1% is tin, and if I was using 30/1 alloy (which I often do), perhaps you can see why it would concern me to allow the alloy to degrade that much.

Sure, maybe all of this being more 'picky' than an individual's shooting ability can support, but consistency does start in the ammunition you make. If you do not allow your alloy to 'mutate' while casting, and your groups resemble 'mutants', isn't it easier to go searching for the cure elsewhere...rather than having to wonder if some of your bullets may have 'slumped', or something?

When I get around to that test, I'll relate my findings...but it could be a while.
CM

[Lloyd Smale]

Only thing ill add to my side of it is your factoring that every bit of that dross is oxidized tin. Im sure most of it is oxidized lead with some tin content and alot of it is just crud. Now if you could show me a test that one of these scientists did that showed that the dross on the top was 100 pecent tin id buy into the fact your loosing to much. NOw i know that isnt the case because you get just as much dross on a pot of pure as you do with any other alloy. Now if your running say 20 to 1 which is 5 percent and the dross is composed even 6040 lead tin. your removing say one once of tin in the 16 oz you put in it which ends up being only a about 6 percent reduction in the ammount of tin in your overall alloy Now if it oxidizes in the same ration it is mixed which would be 95 5 and only 5 percent of that skimming is tin the ammount of tin loss would be so small that nobody could argue that its of any consequence. I may have my head up my but with these figures. Im no math major but a reduction of 6 percent of 5 percent of a mixture doesnt sound like much to me.

[cbrick]

It's also a fact that the two alloys are supposed to have different BHN numbers, '9' for 30/1 and '10' for 20/1. That has an effect on what the BPCR shooter believes about barrel leading control.
CM

Not just barrel leading but groups also. I tested the effect of varying the BHN in long range revolver tests. I used a much wider BHN spread than CM's 1 BHN but shooting a known load from my FA 357 with a 12X Burris at 150 meters from the bench and varying only the bullets BHN by heat treating. A BHN spread of 7 within the same 5 shot group went from great groups to wouldn't even stay on the target at 150 meters.

One of the things that affects the amount of strengthening by heat treating is the percentage of tin. The higher the tin content the less effect there will be from heat treating. As Lloyd mentioned, the amount of hardening from tin in the alloy is minimal though there is some. Add this to the effect of tin on heat treating and there would be differences in BHN from lot to lot. Like CM my goal is maximum accuracy loads at long range and bullet/alloy/BHN consistency does play a part, I have tested the difference.

I have also tested the effect of reducing the antimony content with heat treated bullets. The difference here was rather surprising as the final BHN didn't vary but the the amount of time it took to reach it's maximum BHN increased dramatically.

Two articles that I wrote on these revolver tests may help explain this a bit better.

http://www.lasc.us/HeatTreat.htm
http://www.lasc.us/CastBulletAlloy.htm

Rick

[montana_charlie]

Now if you could show me a test that one of these scientists did that showed that the dross on the top was 100 pecent tin id buy into the fact your loosing to much.
All I can do is re-quote the scientist who said, "For oxidation of high Pb-Sn alloys, tin was preferentially oxidized on the surface, and tin content over the solubility limit suppressed the formation of lead oxide."
When he says 'preferentially oxidized' I take that to mean the tin will oxidize more readily than the lead...perhaps a lot more. And, once the tin content in the dross has reached a certain point, further oxidization of lead will be prevented. But it does not say the oxidation of more tin will actually stop (unless, I suppose, the layer of dross became thick enough to prevent air from reaching the surface).

But, using a dipper, that layer is continuously being disturbed, allowing more oxidation to occur...which will also have a (realtively) high tin content.

My understanding of the scientist's words may be wrong, but that's what I get from him...

Whatever the real story is, I have stated my take on it as fully as I can. You guys can discuss this at greater length, but I'll stay out unless you have a specific question for me...
CM

[leftiye]

Seems to me that this last page might be another thread. The initial issue was whether tin did, or did not oxidize out of the melt. Our personal preferences as to how much we'll do to prevent tin loss are just that- personal preferences. Whatever you are willing to do to get better boolits is your business, but one might ask "If it is as simple as it is to avoid tin loss, isn't it worth it?" I for one actually don't see it as being a waste of time, nor a small deal. I see lots of oxides and they do affect my boolit hardness AND quailty. And I bottom pour.

Lloyd, It is mostly tin (almost all) that oxidizes out of the melt - see the posts where preferential oxidation was discussed. Until the tin is gone that's just about all that oxidizes (except maybe a small amount). Whatever other metals fix oxygen are then reduced by tin (tin takes the oxygen away from them) as long as there is tin available. Lead actually oxidizes (donates an electron to) tin.

[Lloyd Smale]

me too pal. Ive given all the input my little brain has.

[Lee]

Seeing as the title of the thread was "losing tin in the dross", and seeing as ALL the published links all quote that tin is oxidized, and seeing as that the "silence of the experts" has become deafening(!) I WOULD SUGGEST THAT THE TITLE OF THIS THREAD HAS BEEN PROVEN/DECIDED.
Crap oxidizes! Now can't we all just learn to get along, and get back to casting?[smilie=1: .................................Lee:wink: