Keeping the tin in

[armoredman]

I noticed my recast ingots, after casting boolits, are much shinier than when I got them. I believe this means I am minus some tin. Now, should I add tin next time I cast, or is this kinda normal? Is the missing tin still in my pot, cooling down with the inch or so on the bottom? I think I will swing by and grab some lead free solder, just in case, anyway, but was wondering what you guys think.

[randyrat]

My opinion, I doubt you cooked the tin out, unless you cooked the melt for a long while and at a hot! hot! temp. Ingots are usually shiny after they are melted all the oxidation is gone and they are shiny again.. Leave them sit for a while and they will get dull>>months or years. There is a difference of opinion on this subject so hang on to your britches, you may have stirred the pot with this question. The proof in the pudding is; cast some more and test them.

[NVcurmudgeon]

Years ago there was an article in Handloader by a lead company metallurgist. He was not a caster, but a real scientist in his specialty. Among other things he wrote was that LTA alloys do not gravity separate.

[felix]

True when in equilibrium amongst themselves. The equilibrium ratios will change at different temps and pressures. So, if you can really QUICKLY freeze a LTA alloy, you'd be miles ahead. That's why Linotype is so good....equilibrium throughout the entire liquid stage (all elements) and quickly freezes without any slush! ... felix

[Bass Ackward]

Tin burning off at reasonable temperatures always stirs a lot of debate. We have some great minds here. So I am going to ask a question about tin burning off.

You can cook pure lead until you have it super heated and you won't be able to throw a frosty bullet.

Only bullets with some amount of tin get frosty. The higher the percentage of tin, the more frosty the surface gets until you start to see a granular look on the bullets that reduces diameter measurably in that area.

Therefore, if you don't cook out tin at low temperatures getting nice shiny bullets, what explains a frosty bullet?

[Bullshop]

Well Bass I aint no brainiak, and my education went far enough to be able to comunicate and everbody knows I cant spell but one thing I have learned to do is make boolits. I dont know what I am doing wrong but I cant frost any boolits with just lead and tin no matter how hot I cast. Now if theres any antimony in the alloy they sure nuf will frost. When I cast pure lead or lead tin all I get is shiney no matter how hot. As far as the tin burning off I aint a gonna be no help cuz as far as I am concerned you dont need tin to cast good boolits. As I know you know there is another reason to add tin when there is antimony in the alloy but thats a differant deal.
For my money I dont need it in there so I dont give a hoot weather it burned off or not. As far as wearing out barrels without it, hay it happens. Barrels wear if you shoot anything through them. If ya just hang um on the rack where they just look perty they last a good long time but if ya shoot um they wear. Like your car, its good for about 200,000 mile weather ya burn 70%, 80%, or 90% octain. Barrel life is relative to its purpose. A BR shooter dont get so many shots from his as a rabbit hunter does.
When I was hunting fur for a living I had a Rem 22/250 that I had shot so much I could drop on a 60gn bullet and chamber a sized case behind it and not get a mark on the bullet. I sold that rifle to a fella and a short time latter asked him how he liked it. He said GREAT I LOVE IT, its the most accurate rifle I own and I can hit a beer can at 100 yards every time. Relative!
BIC/BS

[armoredman]

Thanks, I was about to do the Geico caveman, "Uh, what?" answer.

[Bass Ackward]

Well Bass I aint no brainiak, and my education went far enough to be able to comunicate and everbody knows I cant spell but one thing I have learned to do is make boolits. I dont know what I am doing wrong but I cant frost any boolits with just lead and tin no matter how hot I cast.

For my money I dont need it in there so I dont give a hoot weather it burned off or not. As far as wearing out barrels without it, hay it happens. Barrels wear if you shoot anything through them. If ya just hang um on the rack where they just look perty they last a good long time but if ya shoot um they wear. Like your car, its good for about 200,000 mile weather ya burn 70%, 80%, or 90% octain. Barrel life is relative to its purpose. A BR shooter dont get so many shots from his as a rabbit hunter does.


Dan,

Gee thanks, now you have me concerned. My 20-1 does frost lightly at 750 degrees if I use steel and cast too fast, but I never have pushed it to see if it gets worse or not. Now I am wondering how "pure" my pure lead is.

So are you saying that frost is antimony loss?

Barrel wear? Where did that come from? Wear is an issue worth considering to each new member. Especially if they have inherited older fire arms of value to them. To consider wear, one must be informed to it's existence. Then the variables that can minimize it can be considered if they are applicable in your situation.

Regardless of your view point though, when you are paying to put tin in there, you do care iffin it stays. :grin:

[Nueces]

Bass, to address your question about 'frosties', I'll paraphrase Dennis Marshall from the NRA Cast Bullets book.

"Another consequence of eutectic shrinkage is 'frosty bullets.'" With too high an alloy temperature, cooling time is extended, allowing free lead in the alloy to form dendrite (tree shaped) crystals, with the still fluid eutectic alloy component interspersed between the branches of the dendrites. The eutectic cools last and shrinks, leaving dendrites standing microscopically proud of the bullet surface, causing the frosty appearance. More rapid cooling means smaller dendrites and smaller differential cooling rates for free lead and eutectic - less frost on the surface.

I tell you what, I'd sooner give up some guns than my library, or this board.

Mark

[armoredman]

Ditto on that last.:)

[Bass Ackward]

Bass, to address your question about 'frosties', I'll paraphrase Dennis Marshall from the NRA Cast Bullets book.

"Another consequence of eutectic shrinkage is 'frosty bullets.'" With too high an alloy temperature, cooling time is extended, allowing free lead in the alloy to form dendrite (tree shaped) crystals, with the still fluid eutectic alloy component interspersed between the branches of the dendrites. The eutectic cools last and shrinks, leaving dendrites standing microscopically proud of the bullet surface, causing the frosty appearance. More rapid cooling means smaller dendrites and smaller differential cooling rates for free lead and eutectic - less frost on the surface.Mark


Mark,

Ain't he smart? I like Dennis Marshall's writtings. But you ain't helping me here. Now I am really confused.

I thought we established that lead, tin, and antimony can NOT seperate for any reason once it is mixed.

Now this says that a lead / antimony / tin mix really is cooling at different rates and some things get left behind cause they are now seperated. So when it cools, crap happens?

What caused the free lead if it didn't seperate? What was left behind? Will it go back again? If lead and tin don't seperate according to Dan, then it has to be antimony left.

From that I assume pure lead won't frost because it all hardens at the same time cause there was nothing in there to seperate. And pure lead melts at 600+ degrees while lead with antimony melts melts at 475 degrees which is about the same as a lead tin mix. So this mix that can't seperate, does when it cools? Like adding sprues and such to the pot?

My brain hurts, thank you very much. :grin:

[9.3X62AL]

And all this time--ever since 11th grade--I was thinking that the Dendrites and the Eutectics were warring Greek city-states of the Periclean era. Or 80's big hair rock bands. Thanks for setting me straight.

Is this place great, or what?

[Nueces]

Al: HAR!

Bass: All this separatin' is taking place at the microscopic grain level, as the alloy cools, sliding down the temperature line on the phase diagram. Ain't that a pretty word picture? (If I say so myself, it beats 'crap happens' :mrgreen: )

The chemistry of the intermetallic compounds differs for different temperatures, so, yeah, free lead can exist (on the metal grain level) even with tin and antimony present, just not on so gross a level that, say, gravity separation happens. Besides, this separation is occuring during cooling and crystal grain formation, when the alloy is no longer liquid. This same sort of process also happens with alloy steels. Choosing the temperature that yields the desired grain chemistry and structure allows heat treating.

I believe you're right, pure lead would not frost, though it'd likely oxidize quickly.

Yup, Marshall is smart. And staring at a phase diagram gives ME a headache, and I did research in solid state physics once. I propose a beer on the porch for both of us. :drinks:

Mark

[felix]

.............The eutectic (Linotype, and other "discovered" mixes) cools last and shrinks, leaving dendrites standing microscopically proud of the bullet surface, causing the frosty appearance. More rapid cooling means smaller dendrites and smaller differential cooling rates for free lead and eutectic - less frost on the surface.............

Let's call these so-called frosties: SLUSH.....i.e., no longer "Linotype" or some another eutectic at that temperature or pressure. ... felix


Yep, pass me a cold one also.

[montana_charlie]

I read this thread this morning, then went out to do stuff. While moving irrigation water, running a tractor, and generally playing 'country boy'...this discussion kept bubbling around in the back of my mind.

So, what I'm about to say will probably be somewhat disjointed...and is the result of logical thinking rather than empirical knowledge.

First, I used to believe that tin in an alloy could be 'burnt off' by too high a temperature. I no longer believe that, and I think the old authors of that concept didn't really mean it that way, anyhow.

What I now think is...tin will oxidize faster than lead, so the oxidized metal on the surface of a molten alloy will contain more tin than lead. If that 'scum' is scraped off...a greater percentage of tin will be removed than the percentage of lead.
The cure is not to scrape it off.
Instead, flux the pot in a way which 'reduces' (I think that's the term) that scum so that it changes back into it's original state...and dissolves back into the alloy. Nothing is lost.

Then, there is the 'frost' part of the conversation.
There was the mention of eutectic alloys...and the formation of free lead 'dendrites'. I have never heard that word before, so forgive me if what I say shows a true misunderstanding.
Anyway, I DO know what a eutectic alloy is. 63/37 solder is one of them, and it has no antimony to muddle up my thinking...just tin and lead.

So...you are casting along with your 20:1 lead/tin alloy. You get things running hotter than necessary and you start seeing frost. (I remember making very frosty round balls from lead that I thought was pure...but that was a long time ago...and I might have been wrong about the purity.) But, I CAN get some frost when using 20:1...and I feel sure there is no antimony in my alloy.

We are told the frost is dendrites standing proud. They can form...from free lead...because that lead is not within the eutectic part of the alloy. Considering how little tin is in this alloy, only a small portion of the lead in there CAN be part of the eutectic portion of the alloy. Most of the lead molecules...even though they are evenly distributed throughout the mixture...must be 'free lead' (another term I may not understand correctly).

So, the free lead makes crystals on the surface as it changes to slush and then a solid (because free lead is NOT eutectic)...while the eutectic mix is staying liquid...waiting for things deeper inside to cool down enough for it to solidify. (Remember, one of the aspects of a eutectic alloy is it's low melting temperature.)
Finally, the whole bullet gets cool enough for all of it the become solid.

If I understand it, the outside is going to look frosty, and the inside will not.
And...if I understand correctly...the reason the frost formed is because the skin of the bullet cooled too slowly. It didn't 'freeze' quickly enough, to use felix's term.

To me, that isn't a result of the alloy being too hot...as much as it's caused by the mould being too hot.

My conclusion is...
- A mould that is maintained at 500 degrees (just picking a number) will try to suck heat out of the alloy as soon as it is poured in.
- If the alloy is high enough above it's melting temperature to flow into all the corners before the mould can suck the heat out, you get good fillout...and a quick freeze.

The other side of the coin is...
- If the mould is too hot, the alloy just simmers in the cavity...forming frost...and waiting to cool down.

So, I figure...
- How does a mould get too hot? By casting too fast with a very hot alloy.
- How do you prevent frost? By slowing down, or keeping the pot at a lower setting.
- Which would I prefer? Actually, both. Slow casting is careful casting...and lower temperature in the alloy slows down that oxidation which requires more fluxing TO KEEP FROM LOSING TIN.
CM

[Nueces]

MC, I agree with your understanding of tin 'scum.' Also, with your recipes for avoiding frost. As for the rest, since I got all that from the Dennis Marshall article in the NRA book, I would refer you to his words. Heck, the copyright has surely run out on it, I'll see about posting it if y'all want.

One thing I can speak of from my own knowledge, though, is a bit about dendrite formation. Dendrite is Greek (see, Al? :-D ) for 'tree' and is just descriptive of the shape the lead crystals take - photos are in the Marshall article, by the way. They are three-dimensional and oriented in different ways throughout the boolit. In other words, they don't so much form on the surface as form throughout the boolit volume, and stick out from the surface a teensy bit when they are allowed to form extensively during long cooling times, due either to very hot alloy or (you're right again, here) to a too hot mould. They are then visible as a bit of surface roughness.

Maybe one of our metallurgists would step in and let us have a word about this.

Mark

[armoredman]

OK, now I need a cold one.
Nicely written, BTW, sir.

[randyrat]

Told you to hang on to your britches.....

[454PB]

Another interesting feature.....

I strive for a very light frosty appearance, I think it assures more consistent mould fill out. I always leave the last boolits in the mould. When I remove them after the mould is cold, there is never any frosting.

I did an experiment last January using 75% "pure" lead and 25% linotype. I water dropped these to test the hardening effect. Some of these were air cooled as a control, and they had little to no frosting. The ones that hit the water were extremely frosty, some to the point that they were rejected.

It seems to me that the RATE of cooling has a huge effect on the amount of frosting.

[leftiye]

MC, Neuces, I think this is a right on explanation of frosting. My version is that frosting indicates that the surface of the boolit did not freeze immediately when it came into contact with the mold. Since hearing here on this site that many, probably most casters don't strive for shiny boolits, I've given this some thought. First let me point out the difference between a "light frosting" and the severe frosting that has characteristics of underweight boolits, and boolits shrinking excessively or pulling away form the mold. Obviously, the second is in no way what we want, and it is not what I'm talking about.

Neuces, I agree that crystallization is not limited to, nor oriented to the surface of the boolit. But what we see is still surface crystallization. I do think it is correct that the eutectic metal that solidifies last does withdraw to some extent from the surface, and leave the crystalls roughening the surface. This explains why you get shiny boolits from linotype metal. As someone here said earlier, it all freezes at once ( eutectic alloy) and doesn't withdraw from the surface.

I used to think that shiny boolits indicated high tin content. Recent casting and adding tin have disproven this idea. More tin is not always shinier, probably almost never. I no longer strive for shiny boolits. I want to see all of the machine marks in the mold transferred to the boolit. Having the alloy and the mold balanced hot enough that the mold fills completely, and has time to do so before freezing is what makes this possible.

[Bass Ackward]

Thanks Guys. Much better understanding now. Back to the drawing boards.

[scrapcan]

Another great discussion. thanks guys.

[montana_charlie]

I strive for a very light frosty appearance, I think it assures more consistent mould fill out.

Since hearing here on this site that many, probably most casters don't strive for shiny boolits, I've given this some thought....I no longer strive for shiny boolits.
If you two have taken on the responsibility of representing the majority, I will be the representative for the minority.

I DO strive for that chrome-like appearance, believing that...if a bullet fills the mould right, and weighs right...an exterior that duplicates lead's appearance in it's molten state probably indicates it was cast under something close to ideal conditions.

Another way of stating that is this...
While molten, the alloy is clean, well mixed, able to fill spaces, and...well...perfect.

If I can cause that 'perfect' alloy to take on the shape I need...with the only 'change' being that it has become solid and cool enough to handle...I feel I have made the bullet I want while keeping the alloy in a state which is as close to 'perfect' as possible.

If this causes that single bullet to (also) shoot perfectly...my actual goal...I think the extra care is worth the effort.
CM

[armoredman]

The group is the end result. And the de-leading...:-D

[454PB]

I have to ask you Charlie, have you tried running temperatures high enough to cause frosting? I too worked very hard at casting shiny boolits, and found that I was casting on the edge of the alloy's ability to produce consistent results. When I decided to accept the frosty appearance, I suddenly saw an improvement in consistency, fewer rejected boolits, and better accuracy. When I started casting, the experts at Lyman said frosty boolits indicated a flawed boolit which needed to be returned to the pot. Of course Lyman was using their #2 alloy, which was much higher in tin than the lowly wheelweights I was using.

If I want to make "showgrade" boolits, I use straight linotype. For the rest of my rounds, I simply use a towel to polish off the frosting after the rounds are loaded.

[alamogunr]

I


If I understand it, the outside is going to look frosty, and the inside will not.

CM

Now my head hurts!

Nueces: Which NRA book was the Dennis Marshall article in?

[montana_charlie]

I have to ask you Charlie, have you tried running temperatures high enough to cause frosting?
Not in the sense of 'experimenting' to record the resulting changes in appearance.

Keeping in mind that all of my casting is for large BPCR bullets, and there is no antimony in my alloy. (I have never melted a single wheelweight.)
I start out by increasing temps to the point where I get good fillout, then compare weights to see how consistent the 'insides' are.
I can reach a satisfactory point (in both areas of concern) without frost...so that is where I stay.

As you know, adding a little tin to pure lead will reduce the melting point a certain amount. Add enough to bring the ratio up to 63/37 and the lowest possible melting point is reached.

With that in mind, I have this observation...
I found what I considered to be the ideal temperature for casting 30:1 alloy bullets. I had the metal and mould at (what I figured to be) the top of the temperature range for what I was after.

Then, when I switched to 20:1 alloy, maintaining the same settings (and rythmn) to cast the same pattern, I did get a bit of frosting.

My conclusion...
The extra bit of tin lowered the melting temperature a tiny bit...and the bullets responded by showing a little frost.
I took that as verification that I was running as hot as I could...and still produce bullets that suited me.

I 'removed' the frost by slowing down a little...allowing the mould to run a bit cooler.
Consistency of weight and fillout remained unchanged.

This all occurred in a single (long) casting session when I was trying to produce as many bullets as I could from a borrowed mould...and wanted examples from both alloys.

I have not had occasion to repeat it...or a desire 'experiment' further.

I guess I would say (like my Dad used to)...Now that my mind's made up, Sonny, don't confuse me with facts!


Looking at the whole question from a different perspective, I have another observation...
I spend time (and post occasionally) on the Shiloh forum. There are a good number of top-notch BPCR shooters who are regulars there.

Occasionally, one of those 'serious' guys posts a picture of his reloading room. Some of them have some pretty impressive facilities...usually with several hundred bullets in neat storage blocks visible on the bench.

I have never seen a bullet from one of those guys that didn't look like chrome...and they are the ones who take top honors all over the nation.

That has an effect on one's thinking...
CM

[Nueces]

alamogunr, the book is:

"Cast Bullets", by Col. E. H. Harrison, published by the NRA, 1979

No ISBN, but the Library of Congress Catalog Card Number is 79-89301

It's a collection of articles and other stuff from the American Rifleman, years 1957 - 1979. The books appear to bring $60 - $80 on the used market.

Mark

[leftiye]

Charlie, I don't think we actually have any difference of opinion. Your alloy probably casts shiny booits at the temp that mine makes good boolits that are a little frosty. Not having antimony, your alloy is maybe even hard to get to frost. I don't think (someone will find me wrong) that 50/50 WW/ pure with 2% tin added can make a shiny boolit that isn't wrinkled or not filled out or undersized. Actually hadn't thought of that previously. In the realm of lead tin antimony boolits the only alloy that makes shiny boolits that are filled out might be linotype.

[montana_charlie]

I don't think that 50/50 WW/ pure with 2% tin added can make a shiny boolit that isn't wrinkled or not filled out or undersized.
Having no antimony time under my belt, and never having watched a wheelweight wilt, I'll have to defer to your broader experience.

I shake my head in wonder when guys state things like...
I run my Lee pot wide open all the time.
or
I think the frostier a bullet is, the better it is.
or
I run everything so hot I have to use a wet rag to make the sprue freeze.

All of those concepts are trully foreign to me...but maybe they are requirements when the ubiquitous wheelweight is the basis of an alloy.

Your thermometer, stuck in my pot, might read differently than mine, but I look for a temperature between 700° and 775°...depending on the mould being used.
The only time I ever got above 800° was when I was trying to get unwrinkled bullets from a cavity that turned out to be contaminated (either) with spray-on graphite or anti-sieze compound. Ten minutes in the ultrasonic cleaner allowed me to get back down to normal.

Do yours your way,and I'll do the same. I will no longer be tempted to say "that's wrong" when somebody says high temperature (and frost) is better.

But I reserve the right to think so (in my no-antimony state of ignorance).
CM

[leftiye]

Charlie, -Even if I use a bottom pour? (*&^%$#@!) For what it's worth that's the exact temp range I have been casting at lately. I used to cast with lino (no wheelweights) and used to get shiny boolits. So , lately when I tried WW it blew me away that I couldn't get shiny boolits. There is a distinct possibility that WW also have impurity(ies) that add to or cause this. Beyond the eutectic shrinkage theory, that is.

[454PB]

Now I understand, Charlie. Using an alloy with no antimony makes a lot of difference. As leftiye stated, 50/50 lino and pure lead is a great alloy that forms good boolits at low temperatures. Even I can make perfect shiny boolits using that mixture.

[45r]

I cast a few hundred perfect looking 185GC boolits for my 357 Marlin yesterday and got no frosting with 20pounds WW,1pound lino and half pound tin in my rcbs pot.It was full to the top.I have found that I need to clean the alloy with a lot of marvelux and cast at 700 degrees to get the shiney boolits with no shrinkage in the middle.If I went too fast one cavity would have shrunken boolit syndrome.I'd have to skip that one till the mold cooled or place the mold in front of the fan for a while.I only kept the perfect looking boolits.Rejected the SBS boolits and any flawed ones, only ended up with 1/3 of the pot making perfect boolits.Not a lot but I get great groups with the chrome looking boolits.Lee size with gas checks on,then heat treat at 445 degrees for a hour.Lube with BAC in the rcbs luber and half inch groups at 50 yards with the 357 CB.I'm going to fire up the pot and make more boolits tomorrow with the 2/3 pot left over from yesterday.probably do better next time I hope.