Discoloration

[Roundnoser]

I'm not sure if this question has been asked and answered somewhere else in this forum...sorry in advance if it has.

When melting wheel weights (after I flux the pot), I sometimes end up with a film on the top of the melted lead. Sometimes its a gold color, other times its a blue-ish or a multi-colored / rainbow- colored skim. -- Any idea what these skim colors represent? Is it still OK to use?

The rainbow colored film cannot be removed. each time I skim it off, another film will appear within a minute or two.

I'm guessing that the blue and/or rainbow color might be from motor oil or paint that coated some of the weights (???). The gold color skim, maybe tin (???).

Thanks!

[Muddy Creek Sam]

See the sticky on the top of this forum http://www.castboolits.gunloads.com/showthread.php?t=63550

Sam :D

[RobS]

Oxidation..........that's all it is. It's not going to hurt anything and the different colors are different oxidizes. Simply flux again to work the alloy back into a homogenized mix. I flux with sawdust and then flux again a second time with it leaving it on top.

[lwknight]

You are probably getting it hotter than it needs to be.
The hotter you get the melt , the more oxidation you get.
You cannot damage the alloy.

[sagacious]

Yup, hotter than need be. Reduce the temp a bit, and the oxidation/drossing rate slows. The color is actually due to the molecular thickness of the oxide layer-- same as the rainbow colors of gasoline on water.

[Roundnoser]

Great info! Thanks.