Seth_AZ
09-04-2012, 02:13 PM
I had a full Lee production pot full of alloy that I'd had around for many years (10-12) since I had stopped casting after a prior house move, and only just got back into it.
I was having trouble with two different molds getting really well filled out bullets. I suspected that I may have contaminated the alloy with zinc. I'd smelted a huge bucket of wheel weights 12-15 years ago and not known that there even was such a thing as zinc wheel weights, so I'd just melted everything down and cast my ingots.
I removed a few drops of battery acid from my car battery and put a drop or two on one of my ingots, and a drop of this acid on top of three different bullets, two cast recently, and one from a long time ago from known good alloy as a control.
I didn't see any fizzing or reaction with the lead. Either this was telling me my alloy was OK, or else this type of acid isn't correct for this test, or it was too dilute. Since I didn't know what was the correct answer, I decide to flux with some sulfur and see what happens.
I picked up a smallish bag of "soil sulfur" from the local nursery, grabbed my respirator, and plugged in the casting furnace.
I deliberately had the heat turned down quite low to let it come up to temperature slowly. When it was still in the low 600s there was a layer of stuff at the top, possible resembling oatmeal (I read that description on this board from others), and I skimmed it off. I figured that my good alloy would be molten by this time, and that if zinc was floating to the top unmelted it would be good to be rid of it.
After skimming that off, I tried out a little sulfur, maybe a teaspoon full. I sprinkled it onto the top of the alloy. It started turning dark as it melted, and smoked. At some point it caught on fire and was burning with a low blue flame. I was doing this at night so it was easy to see, but the flame was dark enough that during the day it might have been harder to see.
I stirred the molten sulfur in to the lead, and it started forming some lumps in the alloy. At some point it caught on fire again, this time with a greenish flame that was far, far larger and more obvious. Eureka! I'd made some zinc-sulfur rocket fuel about 22 years ago, and I remembered it burning with that same greenish flame.
I had some of this greenish flame on my spoon that I was stirring with, and also on the alloy surface. It made a little crust on top of the alloy, and I broke it up and skimmed it off.
I did this again several times, with larger amounts of sulfur crystals. I'd say I did it with up to two tablespoons at a time, and I did it about 4 times in all. Each time I'd get to a point, while stirring, that it ignited that large green flame and burned out, at which point a hard crust was formed on top of the alloy that I'd have to break up and remove. The alloy level in the pot dropped by like an inch throughout this process.
I did not keep fluxing with sulfur like this until it stopped igniting at all. I just noticed a reduction in the size and intensity of that flame at one point, and then fluxed it once more after that.
I then fluxed with some wax, and the alloy was looking good so I put my thermometer back in to do some casting, and found that the alloy temperature was up to nearly 900 degrees! Holy ****, batman! The power setting on my furnace should have been good for only around 700 degrees or so, so I figure the rest of that heat came from the intense exothermic zinc/sulfur reaction.
Anyhow, I proceeded to cast up several hundred of my 9mm bullets, running out the rest of that pot of alloy. They were nearly perfectly cast right from the very first casting (not that surprising I suppose if the alloy really was that hot to start with). The alloy temperature quickly dropped and I casted out the whole pot with the temperature usually in the low to mid/upper 600s.
The ease of getting nicely filled out bullets so quickly, and at as low a temperature as that, convinces me that my sulfur fluxing really was removing zinc from the alloy, and that enough zinc had been removed to improve the casting ability of my alloy considerably. I doubt that it's 100% gone, since I didn't keep fluxing until no more reactions took place. Whatever remains apparently isn't hurting me though.
Here are my observations:
1) I don't know why I got no fizzing or reaction from the car battery acid onto the alloy ingot and cast bullets.
2) I'm really, really glad I wore the respirator.
3) Some of the sulfur fumes got into my eyes a couple times and they stung a bit. I was careful to stay out of it after that.
4) The zinc-sulfur reaction is fairly energetic. Be very careful to do this in an area that won't catch on fire. Wear long sleeves and good leather gloves.
5) I've still got crusty zinc/sulphur slag stuck to my fluxing spoon and around the top insides and rim of my casting furnace. I ran the furnace empty last night and poured the last tiny bit out into my ingot mold so I could give it a thorough wire-brush scrubbing prior to my next casting session.
I lost a considerable volume of my alloy doing this. Like I mentioned, the alloy level went down like an inch or so in the pot over all the fluxings I did with the sulfur. I really hope that slag is all zinc/sulfur ****, or I wasted a lot of alloy.
Anyhow, if you more experienced guys have any comments, I'm all ears. This was my first time doing this, and I put up my experience like this in case I'm misunderstanding something, doing something wrong, or in any other way you guys have comments that would help me or others do this better.
I was having trouble with two different molds getting really well filled out bullets. I suspected that I may have contaminated the alloy with zinc. I'd smelted a huge bucket of wheel weights 12-15 years ago and not known that there even was such a thing as zinc wheel weights, so I'd just melted everything down and cast my ingots.
I removed a few drops of battery acid from my car battery and put a drop or two on one of my ingots, and a drop of this acid on top of three different bullets, two cast recently, and one from a long time ago from known good alloy as a control.
I didn't see any fizzing or reaction with the lead. Either this was telling me my alloy was OK, or else this type of acid isn't correct for this test, or it was too dilute. Since I didn't know what was the correct answer, I decide to flux with some sulfur and see what happens.
I picked up a smallish bag of "soil sulfur" from the local nursery, grabbed my respirator, and plugged in the casting furnace.
I deliberately had the heat turned down quite low to let it come up to temperature slowly. When it was still in the low 600s there was a layer of stuff at the top, possible resembling oatmeal (I read that description on this board from others), and I skimmed it off. I figured that my good alloy would be molten by this time, and that if zinc was floating to the top unmelted it would be good to be rid of it.
After skimming that off, I tried out a little sulfur, maybe a teaspoon full. I sprinkled it onto the top of the alloy. It started turning dark as it melted, and smoked. At some point it caught on fire and was burning with a low blue flame. I was doing this at night so it was easy to see, but the flame was dark enough that during the day it might have been harder to see.
I stirred the molten sulfur in to the lead, and it started forming some lumps in the alloy. At some point it caught on fire again, this time with a greenish flame that was far, far larger and more obvious. Eureka! I'd made some zinc-sulfur rocket fuel about 22 years ago, and I remembered it burning with that same greenish flame.
I had some of this greenish flame on my spoon that I was stirring with, and also on the alloy surface. It made a little crust on top of the alloy, and I broke it up and skimmed it off.
I did this again several times, with larger amounts of sulfur crystals. I'd say I did it with up to two tablespoons at a time, and I did it about 4 times in all. Each time I'd get to a point, while stirring, that it ignited that large green flame and burned out, at which point a hard crust was formed on top of the alloy that I'd have to break up and remove. The alloy level in the pot dropped by like an inch throughout this process.
I did not keep fluxing with sulfur like this until it stopped igniting at all. I just noticed a reduction in the size and intensity of that flame at one point, and then fluxed it once more after that.
I then fluxed with some wax, and the alloy was looking good so I put my thermometer back in to do some casting, and found that the alloy temperature was up to nearly 900 degrees! Holy ****, batman! The power setting on my furnace should have been good for only around 700 degrees or so, so I figure the rest of that heat came from the intense exothermic zinc/sulfur reaction.
Anyhow, I proceeded to cast up several hundred of my 9mm bullets, running out the rest of that pot of alloy. They were nearly perfectly cast right from the very first casting (not that surprising I suppose if the alloy really was that hot to start with). The alloy temperature quickly dropped and I casted out the whole pot with the temperature usually in the low to mid/upper 600s.
The ease of getting nicely filled out bullets so quickly, and at as low a temperature as that, convinces me that my sulfur fluxing really was removing zinc from the alloy, and that enough zinc had been removed to improve the casting ability of my alloy considerably. I doubt that it's 100% gone, since I didn't keep fluxing until no more reactions took place. Whatever remains apparently isn't hurting me though.
Here are my observations:
1) I don't know why I got no fizzing or reaction from the car battery acid onto the alloy ingot and cast bullets.
2) I'm really, really glad I wore the respirator.
3) Some of the sulfur fumes got into my eyes a couple times and they stung a bit. I was careful to stay out of it after that.
4) The zinc-sulfur reaction is fairly energetic. Be very careful to do this in an area that won't catch on fire. Wear long sleeves and good leather gloves.
5) I've still got crusty zinc/sulphur slag stuck to my fluxing spoon and around the top insides and rim of my casting furnace. I ran the furnace empty last night and poured the last tiny bit out into my ingot mold so I could give it a thorough wire-brush scrubbing prior to my next casting session.
I lost a considerable volume of my alloy doing this. Like I mentioned, the alloy level went down like an inch or so in the pot over all the fluxings I did with the sulfur. I really hope that slag is all zinc/sulfur ****, or I wasted a lot of alloy.
Anyhow, if you more experienced guys have any comments, I'm all ears. This was my first time doing this, and I put up my experience like this in case I'm misunderstanding something, doing something wrong, or in any other way you guys have comments that would help me or others do this better.