Molten lead color

[webby4x4]

Hi all - I was doing some casting this weekend and noticed that I couldn't quite keep the color of the molten lead a shiney silver color (like quicksilver / mercury).

Instead, it was more of a gold color, with a thin skin on the top.

I fluxed 5 or 6 times, but it would keep doing that within a few minutes of me fluxing the lead. I also turned the temperature down too, but it didn't seem to make much difference.

The mix started as pure lead and I added 95/5 (tin / antinomy respectively) fluxless solder to the mix.

I should have taken a picture (I will next time), but was curious if anyone knows what would cause the lead to form a thin skin of gold "scum" on the top.

P.S. The boolits cast perfectly (nice a clean, sharp edges, good fillout, etc.) and the lead is also very clean.


thanks,
Rick

[sheepdog]

I get this alot too. Not sure if its high tin content or too hot but I see it alot. Most of all when I got the ol Lee 10 pounder rolling at 8.5 trying to get a tough mould to fill out.

[webby4x4]

I get this alot too. Not sure if its high tin content or too hot but I see it alot. Most of all when I got the ol Lee 10 pounder rolling at 8.5 trying to get a tough mould to fill out.

I'm running the same pot and typically set it around 8.5 myself.

I tried turning it down to about 6.5, but I started to get some folding in the boolits, so I ran it up to about 7.5 and that was about the minimum temp I could go with - didn't seem to make a difference.

[runfiverun]

gold is a good indicator of tin.
pure lead will usually show a blue/purple color.
put a heat barrier on top of your mix it will also help keep the oxides down and the temp more consistant.

[Bret4207]

It's the heated tin oxides.

[jdgabbard]

gold is a good indicator of tin.
pure lead will usually show a blue/purple color.
put a heat barrier on top of your mix it will also help keep the oxides down and the temp more consistant.

Mine (when I get great fillout and boolits that drop a little oversized) is run at about 7 - 8 on a Pro-4 20 pound pot...

At that temp I my alloy Turns kinda golden, then turns blue...then purple.

Once I finally got a thermometer I checked to see what temp I was running at. About 800 - 850. Sometimes buries the needle. Guess I need to start adding a little more tin to my WWs to keep the fillout and keep the temp down. :roll:

[webby4x4]

put a heat barrier on top of your mix it will also help keep the oxides down and the temp more consistant.

Heat barrier... is that a fancy term for a lid?

[hammerhead357]

Could be a lid or like some of us use a layer of new unsented kitty litter. I use a layer about 3/8 in. thick. It does wonders. I flux with it sitting on top of the melt.
A word of warning let it sit on top of the melt for about 5 min. before stiring the melt to flux. This will drive the moisture out of the litter.
Oh yes I think powdered charcoal will work and would be a good flux. I just haven't tried it but I think some here do use it......Wes

[Jaybird62]

I got some of the blue/purple last week from smelting some roof flashing. I also got the gold color when I smelted some old plumbing pipes and what looked like very old ingots poured into the ladle end of a hammer mold. The ingots from the flashing is so pure that I can bend a 1-pound RCBS ingot with my hands.

[runfiverun]

with my 40 lb pot i use the kitty litter and a 1/2" piece of steel as a lid it's a great place to set my molds too.