Blue residue

[REDBARON]

During my last smelting session, wheel weights into ingots, I had a dark blue film (never had before) on top of the melt. Removal was easy enough, fluxed several times (paraffin), and the residue-film would come right back to the surface. Happened a couple of times during the session. Lee 20 pounder, 650 temp. Any ideas what it was.

[oldpara]

During my last smelting session, wheel weights into ingots, I had a dark blue film (never had before) on top of the melt. Removal was easy enough, fluxed several times (paraffin), and the residue-film would come right back to the surface. Happened a couple of times during the session. Lee 20 pounder, 650 temp. Any ideas what it was.

I had that same issue a few years ago.
I thought I'd dumped the (tainted) stuff but every so often I run into it again.
I wish I could tell what it was that I got into but I'm as much in the dark as you.
I still have some ingots marked "Blue" on them.

[DLCTEX]

I think that is lead oxide. Did you have a high percentage of stick ons in the batch?

[Cherokee]

Don't worry about it, fairly pure lead wil get a blue hue some time.

[quilbilly]

"blue lead" is what I consider the good stuff for alloying. Blue lead is soft and almost pure. I make fishing jigs commercially and whenever I get a batch of "blue", I save it for either boolits (mixed with tin and lino) or use it to make special order bendable salmon jigs.

[Marlin Junky]

During my last smelting session, wheel weights into ingots, I had a dark blue film (never had before) on top of the melt. Removal was easy enough, fluxed several times (paraffin), and the residue-film would come right back to the surface. Happened a couple of times during the session. Lee 20 pounder, 650 temp. Any ideas what it was.

Yeah, it's the color of shinny metal when it hits about 500-525F. Turning the temp down to about 450F will give kind of an amber color. Turn it up to about 550F and it will be bright blue. Obviously and assuming you are actually taking that 650F reading with a good thermometer, it's not valid at the top of the melt. The color at 650F should be gray. Is your thermometer reading the temp near the bottom of the melt?

MJ

[44man]

My guess is too many stick on weights that were pure lead. Pure oxidizes blue.
I stay away from stick on weights since I started finding zinc.
Last time I sorted them to melt by themselves and had a pot full of hard to melt oatmeal so I threw the junk out.

[Marlin Junky]

My guess is too many stick on weights that were pure lead. Pure oxidizes blue.
I stay away from stick on weights since I started finding zinc.
Last time I sorted them to melt by themselves and had a pot full of hard to melt oatmeal so I threw the junk out.

Stick on WW are a great source of soft Pb (outside the Pinko States). Two easy ways to eliminate the possibility of introducing Zn into your casting is:

1) Check hardness with an old kitchen knife

2) Set your furnace temp below 700F when rendering WW's into ingots so the Zn (or steel) WW's float to the top (Zn melts at 787F).

MJ

[mold maker]

My old household pliers haven't failed me yet. The lead SO weights squish like butter while the FE and Z are hard as a rock.

[44man]

Stick on WW are a great source of soft Pb (outside the Pinko States). Two easy ways to eliminate the possibility of introducing Zn into your casting is:

1) Check hardness with an old kitchen knife

2) Set your furnace temp below 700F when rendering WW's into ingots so the Zn (or steel) WW's float to the top (Zn melts at 787F).

MJ

I run smelt at about 600* for clip on weights. Anything that floats goes.
It was the stick on weights I sorted out that had the zinc. They have never gone into my smelt but I thought I could get a little pure lead---not to be. Don't need it anyway, I must have a ton or more of pure.
Most of the stick on weights are painted so it can take time to melt and it will throw you off.
Even if they were pure lead, they do not go in my clip on ingots. I refuse to test each stick on weight to judge what it is made from.

[REDBARON]

Thanks for all the replies. Great forum and members.

[44man]

My old household pliers haven't failed me yet. The lead SO weights squish like butter while the FE and Z are hard as a rock.

Some guys can smash steel with pliers. Others can't deform silly putty. Not a good test.
What we need is one of those things used at the scrap yard that uses radiation to get a reading on what is in metal.