Oatmeal slush, need help!

[RickinTN]

Hello all,
I've been working with an alloy of about 3.4% antimony, 3.7% tin, and .3% copper. I'm sure my alloy contains arsenic as well, but not sure of the %. When I melt I get a pretty heavy silver "oatmeal" on the top of the melt. Yesterday I took the melt up to about 740 degrees and fluxed two times heavily, the first time with pine sawdust, and the second with hickory chainsaw chips. Each time lighting the sawdust/chips and letting it burn out, then stirring the carbon into the mix, and finally each time "drizzling" the mix through the carbon-oatmeal on top of the pot attempting to melt it back in. It seemed to return some of the oatmeal to the mix but I still removed more dross of carbon/oatmeal mix than I think I should. I think I'm losing antimony to oxidization. I'm pretty sure I'm not losing any tin as I keep the temps under 750 and I don't have any "golden" hue to the color as I would expect from loosing tin.
Any suggestions on what else I should try to get the oatmeal back into the mix, or is it normal for me to have quite a bit of dross containing this oatmeal?
Thanks for your help and suggestions,
Rick

[docone31]

Use vegetable oil for flux, and add a little pure lead.
Keep the heat up and stir. It will blend.

[btroj]

I get the same at times with high Sb alloys. I flux, flux, flux. Use more pine shavings than you think is needed. Keep stirring.

At some point I decide I have mixed in what will mix in and I skim the crud off. I keep the skimmings and at some point they go into a smelt with new scrap.

[kenyerian]

I do what btroj does. Save the dross in a coffee can for reuse later.

[RickinTN]

I'm of course saving it and will later put it in with another batch. I don't want to add any pure as I've specifically mixed components to come up with this alloy. Thus the reason I am concerned with losing antimony. Trying at least to get my rendition of the high copper alloys discussed in another thread. I've had this occur before and wasn't particularly concerned but in this particular alloy I need to do my best to keep it as calculated. If I am losing all the components in equal amounts to the intended alloy I wouldn't be so concerned but I suspect I'm losing antimony and not lead or tin, or copper for that matter at the same rate. Any ideas if the loss due to oxidation is an equal mix of the alloy, or is the antimony "drossing out" as I suspect?
Big question, I know.
Thanks for the responses so far,
Rick

[Jailer]

I get the same thing with my .25% copper alloy. I'm suspecting that it's just a reaction to the cooler outside air causing some of the melt on the surface to return to a semi slush phase. I have to run my bottom pour quite a bit hotter than usual, around 740, and keep a propane torch handy to keep the spout open as it freezes up about every 4 pours with this alloy. I've thought about trying to leave a small piece of steel on top of the pot to act as a cover and see if that keeps the top of the melt from slushing. Maybe next time I cast some.

I say don't sweat it and just cast.

[Doc_Stihl]

After fluxing I take a putty knife and work the oatmeal/carbon into a pile and then mash it against the side of the pot rubbing it back and forth. It seems to get the carbon worked into the dross really well.

[RickinTN]

I just "cooked" another 40lb batch. This time I was out of pine sawdust so I used Hickory chainsaw chips. I fluxed 2 times and each time put over an inch of chips on top of the melt. This time I seemed to have much more carbon and less metal in the dross. Still had a little metal, but I think that is to be expected, especially due to my skills with a spoon. Using more flux than what appears to be needed apparently did the trick.
Thanks for all the responses,
Rick

[runfiverun]

if it's antimony it's usually not silver. [it's usually more grey and foamy]
try turning the heat up closer to 800-f when fluxing, you won't hurt anything.
if it's zink it will reform when you bring the temp back down.

[bangerjim]

I get the same at times with high Sb alloys. I flux, flux, flux. Use more pine shavings than you think is needed. Keep stirring.

At some point I decide I have mixed in what will mix in and I skim the crud off. I keep the skimmings and at some point they go into a smelt with new scrap.

+1 on that. I save all that "stuff" that just will not go away on higher alloy melts. Just melted a bunch of it down on Monday and got ~9# of really good alloy that most would just throw away as crapola.

banger

[BubbaJon]

If you're under 750 and getting oatmeal you wanna get rid of it. Mine was zinc when that happened.
I melted mine in a big pot, fluxed with pine sawdust and the used to ladle to scoop and pour from a height of about a foot. This helped to get the flux mixed in all the way to the bottom and brought that garbage right up to the top. Later I melted that dross bringing up the temp slowly and recovered most of the lead from it - was left with only a few pounds of dross that I just tossed and was done with it. Zinc just isn't worth the hassle.

[GLL]

What is the source of your original alloy? You seem to know its Sn/Sb % very accurately !

Jerry

[geargnasher]

Pour the sawdust to it and cook the hell out of it, 800-900 F for a while and mash the carbon/oatmeal against the sides of the pot as mentioned. Antimony doesn't reduce as easily at casting temps once oxidized, and when you add copper the intermetallic bonds become multiple and complex. When you get it all reduced, re-alloyed and back into solution via heat and flux, you can cool it down a bit and leave the ash on top to prevent further oxidation. Keeping it below 750 will help maximize the tin's flash-oxide barrier on the surface of the pour stream.

Gear

[Stephen Cohen]

Had a friend who used to mix similar concoction, he found he had to use and oxy into melt as well, in order to get all components up to heat. Cant say I ever tried it but he did get good boolits so he may have been onto something.

[RickinTN]

After adding about an inch or more of chainsaw chips and letting it cook for about 20 minutes and stirring most if not all went back into solution. I was covering the mix before but not nearly as much as I used the last time. The 'base metals" of my alloy were some magnum shot and pure. I tweaked the levels by adding some type metal (monotype?) and 95/5 tin-copper solder. All of the metals except the pure were analyzed by a fellow offering that service here not long ago. His machine was not set to detect arsenic but with about 1/3 of my base metal coming from magnum shot alloy I'm comfortable I have enough arsenic to help enhance heat treating. I now have about 60 lbs of this alloy so enough to play with for a while. Two of the benefits to such an alloy as I understand it is enhanced "toughness" and malleability. I haven't had the opportunity to fire any of these bullets and I don't have a way to test "toughness" but I did do a hammer test on a steel plate for malleablilty. I hammered a 30 cal bullet of .940 length down to a thickness of .195". It's diameter "grew" to more than double @ about .700" depending on where I take the measurement and it only began to slightly "crack" in two places on the edges with the last blow. The cracks don't show the crystalline structure I would expect with an antimonial alloy as they are smooth. It seems quite malleable to me and I'm looking forward to range testing some of the bullets. If I understand fluxing properly its purpose is to "starve" the oatmeal of oxygen allowing it to return to the mix or to de-oxidize it. The inch plus of chips on top of the mix did the trick and apparently I was being too stingy with the chainsaw chips. I would love to leave the carbon on top of the pot to cut down on the oxidation but I'm a ladle caster and haven't figured that one out just yet.
Thanks for all the comments and help,
Rick

PS This alloy casts like a dream and I have produced my best bullets to date. My reject rate has dropped to probably less than 5% and I know when I will have a reject most of the time because of a mistake I made in pouring. I've been casting them at about 675 degrees and using several molds, mostly 30 cal.

[zomby woof]

candle wax, melt and start on fire. I think the fire heats up the slush and drops it back in the alloy. Then add some sawdust. Works for me.