problems losing impurities

[brnomauser]

I've just had my second go at casting with mixed results. As discussed in my previous post - http://castboolits.gunloads.com/showthread.php?t=106134 it appears I needed to flux. I was losing a lot of (I assume) antimony and other wanted impurities from my 50/50 Pb/Linotype. It would just appear on the top as powdery crud.

So this time round, I added some parrafin wax and sawdust and stirred a lot. It didn't seem to be going back in, so I started casting anyway. Bullets were horrible - filled with little black particles and voids. I may have got it a bit warm - When I offered a bit of rolled newspaper it caught alight as soon as it hit the melt. When I added more wax or sawdust it burst into flame. It was going all shades of colour then I suspect I saw the melt start to give off vapours. I killed the fan (it's a coal powerd forge) and left it for a while to let it cool a bit.

Then I skimmed all the crud off - which amounted to a lot and kept casting. Bullets were then absolutely perfect - very well filled out, sharp bases and well defined grooves. But now I'm suspicious they'll be really soft as I suspect most of the hardening impurities have been lost. No more started coming out of the melt at the lower temperatures, but is that because there wasn't any left... It was still casting very nicely even when I tried the newspaper thing again and it hardly charred at all.

Does anyone have any suggestions as to how I can reintroduce the anitimony etc. or prevent it in the future? I have more linotype un-smelted.

I know I should buy a thermometer really but I don't have a spare 50 pounds right now. Also, will it really help with my alloy problem?

I'm not that fussed for these bullets right now as they will be low pressure TB loads in my 243. But I want to get this under control as I'll want some decent hunting bullets that I can drive to reasonable velocites with something like 4895 in my 30-06.

[WHITETAIL]

bronomauser, We all have had some problems when we started.
When you get the pot melted take a stick like you use to stir paint.
And stur the mix and scrape the sides and bottom well.
You will see the junk float then skim.:cbpour:

[brnomauser]

bronomauser, We all have had some problems when we started.
When you get the pot melted take a stick like you use to stir paint.
And stur the mix and scrape the sides and bottom well.
You will see the junk float then skim.:cbpour:
Thanks Whitetail. I wasn't expecting an easy ride, and I'm sure it's worth it. I have done the stirring like you say - with a hazel stick. But I'm worried about skimming all the good stuff off the top. In theory this was a clean ingot - I'm suprised it would give off that much crud. I'm worried about skimming off stuff I want in the melt. How do I know?

[Bret4207]

Well, you don't know that you skimmed off anything really, do you? You can take the dross and remelt it and flux the living heck out of it, you'll be left with a lead alloy you can add back in.

The truth will be in the shooting and final results after the boolits cool. If they are well filled and shoot good then you've lost nothing of consequence. Boolit "hardness" is a tool, not a magic bean or system of shooting that yields perfect results. And , that "clean ingot" might not have been as clean as you thought.

Give yourself some time, it'll work out fine.

[Jim]

BRNO, take a look at THIS. (http://www.castpics.net/subsite2/HowTo/BulletCastingForBeginners-USEdition.pdf)

[Mavrick]

You MAY not have had anything to worry about. That dry powder you took off is prolly the very stuff you're trying to get rid of. Antimony and tin when they are in suspension are actually hard to get out. Tin is pretty easy, when it wants to be, partially from heat, partially from contact with oxygen...that's why you flux and stir. Antimony and tin will act more like pond scum than dry powder.
You can reintroduce the stuff you skimmed, flux, then reskim. Take the powder off and throw it away.
Since the boolits were perfect, you prolly(probably) had an excellent mix. How close were the boolits to their predicted weight? If they are a bit heavy, some of the alloy MAY have come out. Lead is the heavy part.
You may have had a contaminate in your smelt...or some in the pot, and not realized it. Just stir it with the wood stick and flux. Sawdust left on top is a good idea. That's the easy way for me, as I use a bottom-pour.
Have fun,
Gene

[brnomauser]

Thanks guys. Well looks like I may have meant to get rid of that (dross) anyway. Thanks for the link Jim, that's a good read