contamination

[PAT303]

I seemed to have developed a problem with my alloy. When I first melt the alloy there is a grey scum on the surface which is supposed to be tin, from what i've read. When I flux, it disappears but ends up covering the bullets. The funny thing is, when I cast with a ladle and pot using the same alloy the problem is'nt there. I cast 50 bullets using the pot,all good, took the alloy out and put in my lee heater and got 50 bullets covered in grey scum.It does'nt seem to matter if I clean the heater or alloy the problem re-appears. Any ideas. Pat

[ron brooks]

From what I've heard it makes me think you might have zinc contamination <sp?>

Ron

[versifier]

If it's zinc contamination, the boolits won't fill out properly, i.e. all the corners that should be sharp are rounded. I would toss the alloy because it is obviously contaminated with something, and clean out the pot.

[ron brooks]

Could it be aluminum?

[felix]

Aluminum acts sorta' like zinc in that it draws in the lead around corners. So, probably not that. Besides, I add a smite of aluminum stearate to the pot (via lube) when I cast with a mold which produces fat gas check shanks. The aluminum pulls the shank in just enough on the bottom for the check to slip on without resorting to a punch or ball bearing to make the check larger. ... felix

[ron brooks]

Hmmm, before the days of zinc worry I always heard of how you needed to watch out for aluminum contamanation. Always thought it was on par with zinc contamination.

Ron

[PAT303]

I thought It could be something like zinc but seem to get it regardless. The bullets cast from the pot with the same alloy are spot on. Should I skim the scum off?

[44woody]

Pat 303 when you were melting down your ww did you by chance have a valve steem in with your mix the reason I ask is my kid and I like to play jokes on each other when I was doing my last melt down I went inside he put in a hand full of them in the pot and I have develope just what you describe I think it is from the ruber that melted and has got into the mix I have casted with it and the bullets are just fine :castmine: 44Woody

[snowman]

is it possible to get zinc out of the alloy, or are you scrooowd?

I tossed a pile of wheel weights into my pot and started picking out the clips, well, one came out with about 3/4 of a wheel weight still attached.....ie, it had started melting, but didn't melt enough (zinc). I'm not sure what else might have gotten in there before, because I had the temp up higher.

[PAT303]

44woody you have a good point. I'm sure that there is no zinc in the melt because in oz there been around for a while but after what everyone's written I'm starting to worry.I'll try skimming the scum off and see what happens. Pat

[garandsrus]

Pat,

The initial grey scum sounds to me like you have a high tin and antimony content in your alloy, which is what you thought also. It takes some heat and fluxing to get this back into the melt, which you are able to do. From everything I have heard and read, you can't get zinc to separate out of the lead solution, so the gray scum is not zinc.

Are you sure the grey scum on the boolits isn't just "frosted" boolits caused by running a mold hot?

Since you only have a problem with one pot and are using the same alloy in both, my guess is that the temperature between the two pots is very different. The one where the grey scum forms would be the cooler of the two pots. Do you have a thermometer to check the melt temp?

Can you post a picture of the boolit you molded from each of the pots?

John

[VTDW]

Pat,

The initial grey scum sounds to me like you have a high tin and antimony content in your alloy, which is what you thought also. It takes some heat and fluxing to get this back into the melt, which you are able to do. From everything I have heard and read, you can't get zinc to separate out of the lead solution, so the gray scum is not zinc.

Are you sure the grey scum on the boolits isn't just "frosted" boolits caused by running a mold hot?

Since you only have a problem with one pot and are using the same alloy in both, my guess is that the temperature between the two pots is very different. The one where the grey scum forms would be the cooler of the two pots. Do you have a thermometer to check the melt temp?

Can you post a picture of the boolit you molded from each of the pots?

John

My first thoughts also but I am a newbie.:confused:

[Bass Ackward]

The funny thing is, when I cast with a ladle and pot using the same alloy the problem is'nt there.

Pat,

If your stuff is contaminated, it's always there. No matter whether you laddle or not.

You probably have a richer tin and antimony mix that needs more agitation and probably a better flux to get to work. Make that puppy smoke and stir with a wooden stick. You need to because I suspect that your bullets are going to weight different from the top to bottom of the pot depending on where they were made if you don't.

[PAT303]

I wish I new about this forum earlier, like 5 years ago. Everyone has good ideas and I'm leaning towards the high tin mix one, because that's what it looks like. I'm on night shift for the next three days so when I'm done I try to skim some off to lower the tin amount see what happens. The alloy started out as lyman No.2 which is very rich in tin to start with. I'll keep you posted. Thanks Pat

[Finn45]

... mix that needs more agitation and probably a better flux to get to work. ...


This problem is my problem. Spotty and sometimes even ugly boolits with Lee 20# tribbler but clean and shiny boolits with old Lyman dipper and also with Rowell ladle. Can't explain it, but I'm lazy in fluxing so Bass might be on the right track here. Or maybe the valve stem theory applies as I've melted bunch of stick on's with that rubber like adhesive tape... Dunno really. But as far as I've seen there's no real problems with those uglier boolits, they shoot good and they hit the target in good order. But... they look a bit like there's some dirt on their surface, so I've been wondering if that really could be a grinding type of dirt...

[PAT303]

Well i've had success. The general feeling was to much tin, so I cut the alloy 50/50 with lead and the problem went away.I won't have to sell my Lee drip'o'matic after all. Pat

[w30wcf]

PAT303,
Glad to hear that you resolved the situation.

I see that there are some misconseptions of what fluxing does. Fluxing only cleans the alloy, it has nothing to do with keeping the lead, tin, antimony mixed together.

This from a metalurgist that certainly knows his stuff. He likened it to sugar dissolving in water. Once it is mixed in and dissolves, it does not separate.

In my earliest days of bullet casting, I decided to run a test to see if that was true. Using Linotype alloy, I started casting bullets from a full bottom pour pot.
I then kept casting until the pot had about 1" of alloy left. I did no fluxing or stirring the alloy after I started casting until I finished.

The result was that the bullets weighed the same from a full pot as they did from the pot after some 75+% of the alloy had been used. If there was any seperation of the elements, the bullets would have increased in weight as the lighter components would have risien to the top. That did not happen.:-D

Happy Thanksgiving.
w30wcf

[Bass Ackward]

PAT303,
Glad to hear that you resolved the situation.

I see that there are some misconseptions of what fluxing does. Fluxing only cleans the alloy, it has nothing to do with keeping the lead, tin, antimony mixed together.

This from a metalurgist that certainly knows his stuff.


Jack,

I want you to do another experiment when you get time. Put some good lino in a pot and heat it up. Flux and remove the dross. Mold a good bullet then turn it off. Repeat this for 5 days and then compare that lino to the origional. You will find bullets do not weigh the same.

Printers had to reconsistute their lino and eventually it had to be replaced. If what you say was true, then they could use the same batch indefinately. Because it came to them refined, (cleaned) right from the start.

You will also find a difference if you laddle too. You will need to flux much more often than if you bottom pour. What ever the seperation process is scientifically or what ever it is called, it does happen.

[garandsrus]

Jack,

My experience when using a high tin content mix (linotype/foundrytype) is that there is a grey sludge on top of the melt while the rest of the pot is liquid. Something seperated and I believe it to be the tin.

To work the grey sludge back into the mix I liberally fluxed with sawdust and a candle, lit the mixture, and stirred. The sludge went away and the top of the mix was shiny. I don't know if the combining of the material was because of the flux or the extra heat that the burning flux generated.

John

[Firebird]

It was the carbon that was introduced into the pot when you lit the wax & sawdust, then stirred. The heat & carbon ripped the oxygen atoms out of the tin oxide, (that grey sludge on top) leaving tin that was re-dissolved into the lead alloy and carbon dioxide that escaped into the air.
If you had used the Marvalux or other boric acid flux, this wouldn't have happened as these fluxes don't contain carbon. They clean the alloy by sticking to any dirt, and helping float the crud to the surface. They also seal the surface of the alloy, protecting it from the oxygen in the air, but they don't reduce metal oxides back into the metal and carbon dioxide they way a carbon containing flux can.

[PAT303]

I think this goes to show that casting is as much a science as a art PAT

[w30wcf]

Hope everyone had a memorable Thanksgiving. We've been away for a few days visiting relatives. Give thanks with a greatful heart........

Bass Ackward,
Now that would be a bit of torture........bringing a pot of alloy up to temp. only to make a few bullets than to shut it off again! :( No doubt, it would be an interesting experiment.

These days, at least 90% of my casting is with w.w. + 2% tin added. I will say that I usually run three different casting sessions from a 20# pot before I add additional alloy. I flux the pot after I fill it and do nothing further to the alloy until I fill the pot again after the level drops to about 1" from the bottom. I will say, that in my experience, bullets from the 3 different sessions do weigh the same.

In your suggested experiment, I can see how possibly the higher content of antimony and tin in linotype, can be lost through oxidation since they oxidize at a higher rate than lead, especially if casting temp is over 700F through several heating up / cooling down sessions. That could be eliminated though through the use of kitty litter sealing the top surface of the melt.

I will say that in my experience in a casting session consuming 8# of linotype over about 1 1/2 hours at 700F, there was no change in bullet weight, indicating that there was no separation of the elements. Now a longer casting session at a higher temperature could have changed things a bit since oxidation takes place more rapidly at higher temperatures.


Printers had to reconsistute their lino and eventually it had to be replaced. If what you say was true, then they could use the same batch indefinately. Because it came to them refined, (cleaned) right from the start.
Yes, I learned that in my youthful bullet casting days back in the 1970's.
In my quest for bullet making materials I found some "Toning Metal" that was used for that purpose. No doubt, during the numerous remelting and pouring sessions, oxidation removed more tin and antimony than lead from the mix. Now if the operation could be done in an airless environment, technically, nothing would be lost.

Interesting discussion.

garandsrus,
Based on the writings of Dennis Marshall, a metallurgist, oxidation is the culprit by which tin and antimony are lost from the melt more rapidly than lead. Reducing the pot temperature (if possible) will slow that process, and sealing the top of the melt will eliminate it.

Sincerely,
w30wcf

[leftiye]

B.A. The issue you refer to probably is about oxidation which occurs on many metals primarily as they become heated up, though it does also continue to some degree to occur while the metal it hot. I don't know why it is so. I keep a layer of that stuff that separates out floating on top of my lead, and keep it smoking with flux, or bullet lube, or rosin,etc.. This is both while the lead heats up, and while fluxing, and also while casting (yep, it's somewhat smoky). It keeps the oxygen away from the lead. The oxygen that tries to get through gets attached to carbon atoms.

[codarnall]

I seemed to have developed a problem with my alloy. When I first melt the alloy there is a grey scum on the surface which is supposed to be tin, from what i've read. When I flux, it disappears but ends up covering the bullets. The funny thing is, when I cast with a ladle and pot using the same alloy the problem is'nt there. I cast 50 bullets using the pot,all good, took the alloy out and put in my lee heater and got 50 bullets covered in grey scum.It does'nt seem to matter if I clean the heater or alloy the problem re-appears. Any ideas. Pat

Ok everybody wants cheap. The best most cost effective and part that really does the job for fluxing keeps the heat in, and irritates Albert Gore by generating greenhouse gases is carbon. So the next time you flux your casting metal use good old sawdust. As it generates CO-2 just add a little more. In fact keep the metal covered with it.

[shotstring]

All the reading I have done supports that same thinking codarnall. Supposedly sawdust is not only the cheapest, but one of the very few fluxing agents that will allow all the good stuff (tin, antimony and lead) to ALL re-oxiginate back into the primary mix.

[leftiye]

30 wcf is technically correct, fluxing removes dirt etc from the alloy (like marvelux except it doesn't stick all over your pot like marvelux). Reducing is what happens when you remove the oxygen from tin oxide and return the tin to the alloy. We indiscriminately use the term fluxing to mean both actions. Anything that burns will reduce oxides (not necessarily well though) best are stearic acid, rosin, 50/50 alox lube, wood shavings.