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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.

popper
09-04-2012, 02:35 PM
greenish flame - normal sulfur burning color. Sure you weren't just pulling out Sb? I get results like that with NO zinc in the alloy. I use a small ladle of S, let it melt(turn red) and push down into the melt. Immediately a hard 'ball' forms. Keep pushing and smashing it until it's gone. Let sit hot for 4 hrs, stir slightly, very good hardener for the Sb/Pb alloy. Clean and oil the exposed part of the pot after cooling, there will be sulfuric acid reside that rots the pot. I guess one could clean it with baking soda. Flux your Sb slag back in, as you had NO acid reaction with the bullets.

Seth_AZ
09-04-2012, 02:55 PM
Popper, thanks for the comments!

There were two distinct flame types. One was a low bluish flame that began very soon after putting the sulfur on top of the alloy and melting it. The other took a little longer to start, and only got going once I'd stirred the melted sulfur into the pot for a bit. I'd say the low blue flame was between an inch and 4 inches or so in height, but once the greenish flame ignited and burned intensely, it was a good two to three feet high.

Are you saying that the two to three foot intense green flame was probably just sulfur reacting with the antimony?

BeeMan
09-04-2012, 04:26 PM
Seth, like this?

http://www.angelo.edu/faculty/kboudrea/demos/zinc_sulfur/zinc_sulfur.htm

williamwaco
09-04-2012, 05:01 PM
Fizzing reaction.

I tried the acid test with the recipe listed to make home made muratic acid and didn't like the results so I bought a gallon of the commercial stuff.

My results were the exact opposite from yours.
I got fizzing from everything I put it on.

Including:

oatmeal infected alloy
lead wheel weights before and after smelting
zinc wheel weights before smelting ( didn't smelt them )
Lead thought to be pure. BNH 5.5
Virgin linotype.
Purchased hard cast bullets
Pulled .38 special factory wad cutter.

I am NOT a chemist but I see very little benefit from the muriatic acid test.


.

Seth_AZ
09-04-2012, 05:45 PM
Seth, like this?

http://www.angelo.edu/faculty/kboudrea/demos/zinc_sulfur/zinc_sulfur.htm
Yeah, that's what the 2-3' high fire looked like once the stuff was ignited.

I don't really know how to interpret the failure of the car battery acid to get a reaction. I just don't know the chemistry. I'm pretty sure that the larger, vigorous and energetic green flame that I saw was the result of zinc and sulfur. If zinc and antimony can produce that as well then I guess all bets are off.

I do know that after I did this I was able to easily cast up a whole pot full of this alloy (well, minus the losses from the crusty dross) and got several hundred very nicely formed bullets, at temperatures lower than I'd been able to use for this same alloy a few days ago.

I tried using a Lee .358 caliber wadcutter mold to see if I could fill out the leading edge (sharp 90 degree corner that's almost impossible for me to fill out well), but I only cast like 4 or 5 times with it last night, and didn't let it really heat up properly. In the few casts I did I didn't get full fill-out, but again it wasn't a really good test.

popper
09-04-2012, 06:24 PM
No fizz with sulfuric acid, no zinc. no flame from sulfur/antimony combining, the flame I got was just sulfur burning. I just pushed it down into the alloy and the flame went out. I did not use a large quantity of sulfur each time, just added more from the little Lee ladle. The crusty stuff is Pb/S/Sb combining. The alloy stinks every time I melt it.

runfiverun
09-04-2012, 09:47 PM
seth do the new [alloy] boolits weight a grain or so more than a normal batch??

Seth_AZ
09-05-2012, 04:00 AM
Hmm, runfiverun, no actually, the bullets I cast last night after the sulfur fluxing were about .6 grains lighter. I noticed, however, that the bullets I cast last night have less signs of sizing on the forward driving band than the ones I was casting while I lapped that mold, using the pre-sulfur alloy. So the alloy seems to have shrunk a little more after casting.

leftiye
09-05-2012, 04:24 AM
BHN? If you removed antimony, they will be softer than the alloy oughta be.

runfiverun
09-05-2012, 12:00 PM
it would, but any zinc left would make it right back up.
remember zinc is soluble and castable in lead alloys.
sulpher makes a tighter grain size within the alloy,but adds surface tension to the outside which would/could cause rounding on the edges if high amounts were present.

Wayne Smith
09-05-2012, 01:10 PM
BHN? If you removed antimony, they will be softer than the alloy oughta be.

And thus heavier, not .6gr lighter.

lwknight
09-05-2012, 09:06 PM
And thus heavier, not .6gr lighter.
Exactly. Removing zinc would also make heavier casts.

Seth_AZ
09-05-2012, 09:55 PM
I agree that makes sense. The fact that the bullets seem to be a little smaller makes this result a little less understandable to me. With my pre-sulfur alloy both driving bands were showing sizing contact going through my Star sizer, while my post-sulfur bullets showed forward driving bands with less than a majority of good sizer contact. I don't know why, and how that affected the weight.

Also, the lack of fizzing when I put a drop of battery acid on the bullets makes it look like there wasn't any zinc in the alloy, and yet I got good strong, vigorous, energetic green flame 2-3' high that looked exactly like zinc and sulfur reacting.

I don't know what's really going on. There are conflicting interpretations of the evidence. I do know that the bullets seemed to cast much more easily with the post-sulfur alloy than before.

lwknight
09-05-2012, 10:07 PM
We may never know the answers to all weird things that make you go " hmmm" but at least you got it going your way somewhat.

leftiye
09-06-2012, 04:08 AM
BHN? If you removed antimony, they will be softer than the alloy oughta be


And thus heavier, not .6gr lighter.

Still worth checking. More data to guess from. Smaller might also be lighter?

Wayne Smith
09-06-2012, 11:27 AM
Also, the lack of fizzing when I put a drop of battery acid on the bullets makes it look like there wasn't any zinc in the alloy, and yet I got good strong, vigorous, energetic green flame 2-3' high that looked exactly like zinc and sulfur reacting.

I don't know what's really going on. There are conflicting interpretations of the evidence. I do know that the bullets seemed to cast much more easily with the post-sulfur alloy than before.

Humm, I am far from being a chemist. No chemistry since High School, and that 'C' was a gift! Is there any other common contaminant that might cause that reaction other than Zinc?

popper
09-06-2012, 05:38 PM
Seth - you have to keep the sulfur UNDER the melt, else it will burn just as you described. Don't sprinkle on top, it will just burn and do nothing but make a flame! When it melts and turns red, push it under, stir. Push any that floats back down. You want it to combine with the zinc which doesn't require burning.

Seth_AZ
09-06-2012, 09:52 PM
Seth - you have to keep the sulfur UNDER the melt, else it will burn just as you described. Don't sprinkle on top, it will just burn and do nothing but make a flame! When it melts and turns red, push it under, stir. Push any that floats back down. You want it to combine with the zinc which doesn't require burning.
Yes. The vigorous green-flame burning only occurred after I stirred the molten sulfur into the melt. While stirring it lumps of stuff would float back up to the top of the melt, and eventually it ignited with that vigorous green flame, and I'd have to step back and let it burn out.

John in WI
09-06-2012, 10:14 PM
I am NOT a chemist but I see very little benefit from the muriatic acid test.


.

I question the use of the HCl test to look for zinc. You're right, HCl WILL fizz in the presence of lead (you're making the metal salt, and the bubbles are hydrogen gas).

I think the trick is that every time I have seen someone report doing the "muriatic test" they are using DILUTE muriatic acid.

The stuff I have seen at the hardware store is 20% muriatic, and I think to run the test you want something around 5%. If you use a dilute but very strong acid it should react very slowly with lead and much more vigorously with zinc. If you use concentrated acid, you get bubbling from both the lead and the zinc.

(I am a chemist!)

popper
09-06-2012, 11:09 PM
Seth - with proper protection, gloves, glasses, etc. just keep pushing the stuff back into the melt, it will stop burning. Kind of scary the first time you do it. I think if there was zinc in there and you made 'rocket fuel' the melt would get 'highly active'. Sulfur needs oxygen to burn, I think the zinc/sulfur doesn't. Never made rocket fuel that way, I used powdered aluminum 60 yrs ago. My .401 sizer does .401 on pure, .402 with Sb. Do they clunk or click when dropped? I've got some WW to smelt, I'll try when the weather here gets much cooler -103 today.

MT Chambers
09-06-2012, 11:32 PM
I woulda thought that 15 years ago they hadn't started using Zinc or anything else but lead for WW?