Charcoal for Flux?

[jackj]

I understand the reason for using sawdust as a flux. And I read chapter 4 of the book in the casting section. However, on the first page of the article on flux the author mentions using charcoal as a flux (think Kingsford), but doesn't mention it at the end where he recommends sawdust for flux. It would seem using ground up charcoal would be ideal?

Input appreciated.

I just realized I've been reading this forum for years...and this is my first post (I'm slow...lol!)

[Pepe Ray]

Economics!!
It's ideal if you can obtain it as cheaply as you can sawdust.

[slide]

I would try it on a small batch. PatMarlin on this site sells the best stuff I have ever used. I don't know how it compares to straight sawdust cost wise and I don't care. It works great. Pat has been sick,I don't know how he stands on flux.You might send him a pm.

[stubshaft]

I would try it on a small batch. PatMarlin on this site sells the best stuff I have ever used. I don't know how it compares to straight sawdust cost wise and I don't care. It works great. Pat has been sick,I don't know how he stands on flux.You might send him a pm.

Pat's World Famous Flux is more expensive then sawdust which you can usually beg for at a mill for free. That being said I would STILL buy some more of Pats flux from him because A, it smells great, B, works great and lasts a long time. I still have about a half a box of it from my last purchase about 4 years ago.

BTW - Kingsford charcoal may work fine (I don't see why it wouldn't) but remember that it uses coal as a binder.

[winelover]

Been using Kingsford as a flux now for about a year. Put briquettes in a metal coffee can and smash with an old wooden baseball bat. Sort of morter & pestle.

Winelover

[geargnasher]

Sawdust both fluxes and reduces. The fluxing comes from its ability to draw and capture specific things boolit casters consider impurities (calcium, alumium, iron, etc) from a ternary lead/antimony/tin alloy without absorbing any of the metals we want to keep.

The reducing comes from two actions, both with the same goal of reacting with lead/antimony/tin oxides in a way that removes the bound oxygen and leaves elemental metals behind. One action is by sacrificing carbon and gaining oxygen with heat as a catalyst so that CO2 gas is created and pure metal left behind, the other is by the actual thermal decomposition (smoldering/burning of the "flux" or reducing agent) which makes a more reactive reduction/oxidation reaction because during combusion, carbon monoxide (CO) is produced which pulls oxygen from the oxidized metal and makes CO2 gas.

Basically, anything that will burn will act as a reducant to the oxides on top of the melt, and sawdust also actually FLUXES the metal by isolating and capturing impurities so they can be skimmed and removed with the ash. Sawdust performs both operations very well by itself. Grease/wax/oil only serves to reduce oxides (more so if you ignite it), and inert charcoal will do both operations but very poorly.

Keep this in mind and it should become obvious what will and won't work for the tasks of reducing and fluxing.

Charcoal briquets, obviously, are not inert because they aren't fully burned. While I've never tried it, one single crushed briquet should flux/reduce many pots full of lead if it will smolder on the surface, and I can't imagine that it wouldn't. "Activated" charcoal (activated just means it's very porous and has lots of surface area to absorb things like chlorine and organic vapors) is difficult to burn at casting temps, so it doesn't do much for the reducing part, although I imagine it makes a pretty decent flux.

Bottom line, try it and see. Crush some up and put a 1/8" layer over the top of the whole pot of molten lead. If it glows orange and slowly smolders down, I'd say it's doing its job.

Gear

[rsrocket1]

The coffee can and baseball bat technique is a good idea. I used a hammer and dustpan on the concrete pad of my patio as a mortar and pestal. Yes, one or two briquettes fill up a jar and will last a long time. I think it is as good if not better than sawdust in that it is already a very fine powder and you can control the size of the granuals by how much you bang on it.

Being that there is less moisture in the charcoal than in sawdust, there is less smoldering, but I still wouldn't do it indoors without an exhaust fan. It also leaves a nice layer of ash to act as a barrier against oxidation. It's about as close to free as sawdust if you already have it. A couple of briquettes out of the bag is essentially "free".

[jackj]

It's funny, but at the bottom of every 25lb bag is already a substantial amount of charcoal fragments / dust that would have simply been thrown away. You don't even have to break up a few briquettes to get enough "free" material to use.

[Fredx10sen]

I wonder if shredding the bag in the shredder and mixing it with the charcoal would do any good?? :confused: Might be worth a try?? My shredder does the real small cross cut thing. Although I'll have to do it when the better half isn't looking. :shock:

[Junior1942]

Many years ago I read something which said that the stuff melted into lead was in solution, like salt in salt water. You can't un-solution it. So I stopped fluxing. It made zero difference in my cast bullets. Try it. Unless you like smoke.

[williamwaco]

Sawdust both fluxes and reduces. The fluxing comes from its ability to draw and capture specific things boolit casters consider impurities (calcium, alumium, iron, etc) from a ternary lead/antimony/tin alloy without absorbing any of the metals we want to keep.


Gear


This is sorta off the immediate subject but I have found that repeatedly fluxing with sawdust will improve zinc contamination. I never managed to really clean it completely but it did significantly reduce the "oatmeal". Repeatedly does not mean two or three times - more like six or eight.

[geargnasher]

WW, I never had zinc "oatmeal" on me, but have heard others talk of this. One time I deliberately zinc'd a small batch of alloy to see what would happen, and the worst thing it did was separate into layers on top like oil and water (and of course cast terrible boolits). The "oatmeal" that I've experienced has proven to be low temps and excessive antimony-to-tin ratio, or oxide clumps. Sometimes antimony wants to separate from the lead, or at least remain solid and clump up on top (since it's lighter than lead and floats), and sawdust has proven to be the only thing that will get it to melt back in. I think that's because you can mix the sawdust with the oatmeal and make a big clump of it, which forces the two together under the surface where wax or oil will just burn off the surface.

I would imagine that zinc might be absorbed by sawdust to a certain degree, so I'm not doubting your observations, but there is more than one thing that causes "oatmeal" alloy, and in my limited experience, zinc didn't really do it. With all the "unknowns" in the scrap we use, it's tough to do a truly valid comparison of experiences sometimes.

Gear

[geargnasher]

Junior, you have to stir the alloy, preferably with a stick, to get all the dissolved stuff that will flux out exposed to the flux. Otherwise you're relying on the slow moving thermal current of the pot to do that.

Gear

[nanuk]

Junior, perhaps fluxing causes a precipitate of sorts.

I know where you are coming from, but chemically, sometimes things happen

[bbqncigars]

If you know a serious (no propane) bbq'er, chances are that they use some lump charcoal and would be happy to give you the fines from the bottom of the bag. Unfortunately this idea is a little too late for the bag I tossed last weekend.

[MBTcustom]

I want to second what Geargnasher said about the "oatmeal" stuff on top of the pot. I just went through dealing with this phenomenon and, being the curious type, I had samples of the stuff tested for content. I found that there was no trace of zinc in the samples, or the pot, or the original big pot. I had all three tested with a machine that is so powerful it even recognized .02%-.3% traces of stuff like gallium, nickle, copper, cadmium, and even gold. All of these elements were in my mixture but there was no trace of zinc. I quit using candles and paraphin wax to flux my pot and tried sawdust on recommendations from C-brick. It worked like a charm and all the "oatmeal" alloy was reintroduced into solution in short order. I just wanted to mention it because my conclusions were based on hard evidence and not theories, guesses or assumptions and the results were much different than all the advice that I had been given. Now I dont have to throw out a perfectly good 150Lb. of alloy because I believe that there is zinc in it.

[HARRYMPOPE]

Many years ago I read something which said that the stuff melted into lead was in solution, like salt in salt water. You can't un-solution it. So I stopped fluxing. It made zero difference in my cast bullets. Try it. Unless you like smoke.


I agree.

[olafhardt]

Plant solids such as cellulose, sugar, starch, etc are essentially made of carbon, oxygen and hydrogen. When contacted with molten metals below 900° F the carbon gives up the hydrogen and oxygen to snatch the oxygen off of tin, antimony, iron, nickle, lead, bismuth, copper, silver, mercury and gold. The oxygen left oxidizes metallic zinc, chromium, maganese, vanadium, aluminum, berrilium, magnesium and calcium. Thus the use of a carbohydrates like
sawdust or sugar reduces the desirable metal oxides to the metal and oxidizes the undesirables to floating oxides. Most of the hydrogen and oxygen are driven out of wood turned into charcoal; therefore, it does not have the purifying ability of wood. The hydrogen helps reduce the good metal oxides. I think one could dezincify a melt by blowing it with HOT (700°F?) steam. I never have tried it be careful if you do.

[Longwood]

A friend and myself spent all day teaching another shooter friend the fun of casting bullets.
We smelted about 120 pounds of wheel weights, dive weights, fish sinkers made from solder, and just plain scrap that the student furnished.
Several times I saw the oatmeal during the process and each time I used straight Aspen pet bedding, to turn it right back to clean shiny metal.
I also used the sawdust on the melt in the casting pot while we cast over 400 bullets and I did not see one bad bullet all day long that was caused by junk in them.
The friend that was helping instruct had never used sawdust. Just as I was the first time I tried sawdust, he was amazed at how we ended up without the skim that we had tossed so much of in the past.
Are we completely convinced that sawdust is the way to go?
You Bet!

[Longwood]

Many years ago I read something which said that the stuff melted into lead was in solution, like salt in salt water. You can't un-solution it. So I stopped fluxing. It made zero difference in my cast bullets. Try it. Unless you like smoke.

Many years ago I worked at a Nickle smelter.
Before they sold the nickle, it had to be refined to only contain accepted amounts of other metals such as cromium, boron, etc, etc, etc.
The way they removed the undesirable metals from the molten "Solution" was by fluxing it with very pure limestone.
We proved numerous times today that fluxing bullet metal made from scrap, with sawdust, works extremely well.

[ku4hx]

I like sawdust. It's one of those things you can make fairly simply at home. A few passes of my old circular saw and my garage floor gets covered in it.

And to think for years I swept it up and threw it away. Got me a couple of 5# coffee cans full now.

[Junior1942]

Many years ago I worked at a Nickle smelter.
Before they sold the nickle, it had to be refined to only contain accepted amounts of other metals such as cromium, boron, etc, etc, etc.
The way they removed the undesirable metals from the molten "Solution" was by fluxing it with very pure limestone.
We proved numerous times today that fluxing bullet metal made from scrap, with sawdust, works extremely well.I know zilch about fluxing nickel with limestone. However, I have cast untold thousands of bullets of wheelweight alloy, reclaimed shot alloy, babbit alloy, pure lead alloy, and I fluxed not a single pot of the molten alloy. My did-flux days of old produced no better bullets that my don't-flux days of now. In my considerable experience, fluxing is useful if you believe it's useful or, as I said previously, if you like smoke.

[Longwood]

I know zilch about fluxing nickel with limestone. However, I have cast untold thousands of bullets of wheelweight alloy, reclaimed shot alloy, babbit alloy, pure lead alloy, and I fluxed not a single pot of the molten alloy. My did-flux days of old produced no better bullets that my don't-flux days of now. In my considerable experience, fluxing is useful if you believe it's useful or, as I said previously, if you like smoke.

It turns out, that, was sort of my story also.
I made bullets from anything I could find that looked like lead.
I thought I was fluxing by using wax etc., until I learned better here.
Yesterday, I used sawdust and it worked much better than the way I had always read to do it but, was in reality, a waste of time and desirable metals.
I used to toss out pounds of metals that floated up thinking it was a contaminant now, I simply blend them back into the melt withdry sawdust.

My remark about the nickle smelting process using lime was pointing out to you that you remark about not being able to pull metal from a molten solution, was not correct. They use the same process with many molten alloys.

[jackj]

I guess it's considered the "norm" to flux (reading all the input on this forum). Well, at this point, my choices are either use Corn Cob tumbling media or charcoal as I have access to those materials. I don't have ready access to sawdust

I've been bullet casting for over 30 years, but until this week, had always used wax to flux. It never occurred to me to use this forum to brush up on my casting techniques that I learned from books and experience back in the Stone Age...lol!

[Longwood]

[QUOTE=jackj;1581210]I guess it's considered the "norm" to flux (reading all the input on this forum). Well, at this point, my choices are either use Corn Cob tumbling media or charcoal as I have access to those materials. I don't have ready access to sawdust

[/QUOTE

I use pellets that have been wet so they would swell up and turn back into fine chips, then dried, prior to susng for in the pots, or what we used yesterday, which was Hamster bedding from walmart.

[Longwood]

if you like smoke.



I don't "Like" the smoke Jr.
I "Light", the smoke.:kidding:

From what is being said, that should not only get rid of most of the smoke, it should help burn off the unwanted oxygen.

[SlowSmokeN]

Sawdust both fluxes and reduces. The fluxing comes from its ability to draw and capture specific things boolit casters consider impurities (calcium, alumium, iron, etc) from a ternary lead/antimony/tin alloy without absorbing any of the metals we want to keep.

The reducing comes from two actions, both with the same goal of reacting with lead/antimony/tin oxides in a way that removes the bound oxygen and leaves elemental metals behind. One action is by sacrificing carbon and gaining oxygen with heat as a catalyst so that CO2 gas is created and pure metal left behind, the other is by the actual thermal decomposition (smoldering/burning of the "flux" or reducing agent) which makes a more reactive reduction/oxidation reaction because during combusion, carbon monoxide (CO) is produced which pulls oxygen from the oxidized metal and makes CO2 gas.

Basically, anything that will burn will act as a reducant to the oxides on top of the melt, and sawdust also actually FLUXES the metal by isolating and capturing impurities so they can be skimmed and removed with the ash. Sawdust performs both operations very well by itself. Grease/wax/oil only serves to reduce oxides (more so if you ignite it), and inert charcoal will do both operations but very poorly.

Keep this in mind and it should become obvious what will and won't work for the tasks of reducing and fluxing.

Charcoal briquets, obviously, are not inert because they aren't fully burned. While I've never tried it, one single crushed briquet should flux/reduce many pots full of lead if it will smolder on the surface, and I can't imagine that it wouldn't. "Activated" charcoal (activated just means it's very porous and has lots of surface area to absorb things like chlorine and organic vapors) is difficult to burn at casting temps, so it doesn't do much for the reducing part, although I imagine it makes a pretty decent flux.

Bottom line, try it and see. Crush some up and put a 1/8" layer over the top of the whole pot of molten lead. If it glows orange and slowly smolders down, I'd say it's doing its job.

Gear

Gear, very informative, thank you.

[geargnasher]

I guess it's considered the "norm" to flux (reading all the input on this forum). Well, at this point, my choices are either use Corn Cob tumbling media or charcoal as I have access to those materials. I don't have ready access to sawdust

I've been bullet casting for over 30 years, but until this week, had always used wax to flux. It never occurred to me to use this forum to brush up on my casting techniques that I learned from books and experience back in the Stone Age...lol!

I am absolutely astonished that anyone living in America would not have access to sawdust. Ever town in the country that has a lumber yard almost always has saws, and anywhere that has trees has firewood and people who cut it.

Cabinet shops are great because they have planers and shapers the generate nice shavings and chips which will be mostly hardwood, as opposed to the sawdust they generate which will be mostly plywood, not good due to the formaldehyde glue in most plywood. I'm sure a short friendly chat with any woodworking or furniture shop owner would yield you a coffee can, or perhaps a pickup load of planer shavings free for the taking.

If you truly don't have any good way to scrounge something, many people here report that our vendor PatMarlin's California Flake Flux is second-to-none and a medium FRB is around $20 or so, probably a lifetime supply for casting and smelting.

Gear

[milprileb]

One must be using some really pure metal to not need any fluxing at all. I am not
using such virgin materials obviously ! For me, the saw dust has proven to be a
wonderful solution in my bottom pour pot to drop clean metal and keep pot clean as well.

My recommendation to anyone is to use sawdust and flux. YMMV.

[Junior1942]

One must be using some really pure metal to not need any fluxing at all. I am not using such virgin materials obviously ! ......If you're referring to me, junkyard wheelweights and re-claimed shot aren't pure metal. Fact remains: I haven't fluxed a pot of bullet alloy in maybe 30 years and many thousands of bullets. However, if a person feels the need for ritualistic mumbo-jumbo and a plume of smoke, who am I to argue? Drum beats and chants are ok, but please don't sacrifice a virgin.

[happyret65]

Feathers ok?

[Junior1942]

Feathers ok?Turkey only.

[Sawdust]

tallow works for me.

[geargnasher]

Junior, your opinions do not change the physical laws of nature.

If you don't feel the need to flux out impurities and reduce tin and other valuble oxides back into the melt, then don't, but if you've never fluxed properly, how the heck would you know whether it does any good or not?

Mr. Sawdust, tallow might work for you, but how's it really working for your alloy?

Gear

[Sawdust]

For 30-1, 25-1, 20-1 reduces tin quick and simple.

[Wayne Smith]

Feathers ok?

As long as you don't mind the stink!

[Junior1942]

This outta help: http://youtu.be/N7DPUz3pOk0

[Bob Krack]

I got a funny feeling she was staring at me.

[williamwaco]

I want to second what Garnishee said about the "oatmeal" stuff on top of the pot. I just went through dealing with this phenomenon and, being the curious type, I had samples of the stuff tested for content. I found that there was no trace of zinc in the samples, or the pot, or the original big pot.

I find this extremely interesting. I just "assumed" it was zinc for two reasons.

1) That is what this phenomenon has been called here. I never heard of it or saw it until I joined this forum.

2) The only times I have seen it is during smelting sessions while smelting wheel weights.

No amount of fluxing with wax or stiring will get rid of it. Fluxing will not cause it to recombine and after scraping off a half inch of the stuff, in five minutes another half inch layer will form, etc. until the pot is empty. Curiously, if I ignore it, leave it on top and cast bottom pour, the metal under the oatmeal will cast perfect bullets. Well formed, correct weight and diameter.

As Gear says, If I flux with sawdust it makes charcoal like clumps I can remove. Each time the layer gets thinner and less stuff and after a while it appears to be mostly clean.

SO:

If it is NOT zinc? what causes it?

Inquiring minds want to know. . .



.

[geargnasher]

Williamwaco, that sort of "oatmeal" is frozen antimony (metallic), antimony (oxide), and tin (oxide). Probably a lot of lead oxide in there too, plus who knows what else like aluminum, calcium, iron, etc.. The metallic antimony on the surface is insulated by the other oxides so it won't melt at regular casting/smelting temps, and of course neither will the oxides. When you add your sawdust and initiate the reduction/oxidation reaction, the reduced tin and antimony oxide mixes with the metallic antimony which lowers its melting point, and the whole lumpy mess vanishes into solution leaving only smoldering ash on top for you to skim clean or leave as an oxygen barrier. Having the alloy temperature elevated near the critical point of tin (near 750 degrees) helps a lot, too, since the additional heat enhances the whole redox reaction.

I discovered something interesting a couple of years ago that I've never seen mentioned anywhere. When any typical boolit casting alloy is heated much above 750 degrees, it's just about impossible to get the surface skimmed shiny. The tin oxidizes instantly into a thin film on top of the melt and continues to thicken as time progresses. This skin won't reduce back in until the temp is lowered. I wonder how many people are running their pots (knowingly or not) upwards of 800 degrees and wondering why all this "fluxing" isn't doing them any good!

Gear

[Sawdust]

I discovered something interesting a couple of years ago that I've never seen mentioned anywhere. When any typical boolit casting alloy is heated much above 750 degrees, it's just about impossible to get the surface skimmed shiny. The tin oxidizes instantly into a thin film on top of the melt and continues to thicken as time progresses. This skin won't reduce back in until the temp is lowered. I wonder how many people are running their pots (knowingly or not) upwards of 800 degrees and wondering why all this "fluxing" isn't doing them any good!

Gear

Lyman Cast Bullet Handbook 3rd Edition has some good information on this on page 48 under the heading - High Temperature Casting.

They say at 750*F small amount of oxidation at this temperature.

They also talk about extremely high temps and the loss of tin.

"95Pb-5Sn at 1050*F. The majority of the tin drossed off in 30 minutes"

[geargnasher]

I was talking specifically about reducing the oxides back in as long as the melt was above 750: I haven't been able to do it with anything as long as the temp was above 750. Cool the alloy below that and the tin and whatnot easily reduces right back in with grease/wax/oil/ or sawdust.

Gear

[williamwaco]

. . .

I discovered something interesting a couple of years ago that I've never seen mentioned anywhere. When any typical boolit casting alloy is heated much above 750 degrees, it's just about impossible to get the surface skimmed shiny. The tin oxidizes instantly into a thin film on top of the melt and continues to thicken as time progresses. This skin won't reduce back in until the temp is lowered. I wonder how many people are running their pots (knowingly or not) upwards of 800 degrees and wondering why all this "fluxing" isn't doing them any good!

Gear

This is also interesting to me because I have also noticed that ( my ) oatmeal forms only when smelting clip-on wheel weights and only when I get distracted and let the pot "cook" for 20 to 30 minutes before fluxing.

Once they are smelted, well fluxed, well cleaned, and poured into ingots, they will not oatmeal again.

BUT

If I attempt to make ingots with this metal with the oatmeal present, the ingots willl have a frothy little volcano at the point the stream enters the ingot mold, and when these ingots are remelted, they will immediately oatmeal. I can tell at a glance by looking at an ingot if it will make oatmeal when it is melted.



.

[Sawdust]

I was talking specifically about reducing the oxides back in as long as the melt was above 750: I haven't been able to do it with anything as long as the temp was above 750. Cool the alloy below that and the tin and whatnot easily reduces right back in with grease/wax/oil/ or sawdust.

Gear

Agree with this. It is stated several times in the Lyman Cast Bullet Handbook 3rd Edition. 750°F is the threshold above where, oxidation problems arise.

Tried high temp casting with 4 different pots. Waage 20#, Lyman Mag 20, Lyman 10#, Lee 10# and could never get them hot enough to use Boric Acid as an effective barrier. The oxides would clump up with the Boric Acid. Was able to make this work, once, using a propane turkey burner that is used for 100# alloying batches. But the problem then becomes toxic lead fumes. Tradeoffs.