High purity gold slag colors

[autumnwillow]

I know I've read it somewhere here in the forum about slag colors when melting high purity gold powder but I can't seem to find it anymore. Does anybody have the link to it?

 

[anachronism]

Melting high purity gold you shouldn't be using much borax at all.

Your dish should have a slight reddish tinge afterwards and any borax (if any visible at all) should be clear.

 

[snoman701]

You are probably thinking more along the lines of seeing purplish haze, or even purple slags, which could indicate the presence of silver chloride carrying off some of your gold.

Pure gold can be melted readily without flux. And as Jon pointed out, if flux is used it should be clear once melted.


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[autumnwillow]

So what does a clear borax with golden tint indicate? This is the first time that I have seen it. I'll take a photo later.

 

[nickvc]

I always kept my used fluxes and re ran them with a thinner and just let them sit in a hot furnace for an hour with regular stirring and then pour into a cone mold or a large mold angled to allow the metallics to settle at one end, the mold needs to be hot. The remaining flux I then crushed and sieved to remove any beads which were added to the original bar and reprocessed, my fluxes always ran fairly high in silver from melting karat scraps so inquarting was needed. Any remaining powders from the flux I kept for later processing to scavenge any remaining values.

 

[autumnwillow]

For inquarted gold I pour the slag along with the inquarted gold and process them the same way. Its not much slag anyway. Any small particles that gets too fine are captured by my sink trap.


It looks like gold stuck in the flux.

 

[anachronism]

If it's borax- - make a weak solution of H2SO4 and heat the crucible in it.

It'll dissolve the borax and leave your prills of gold.

 

[glorycloud]

If it's borax- - make a weak solution of H2SO4 and heat the crucible in it.

It'll dissolve the borax and leave your prills of gold.

Stellar! Thanks for that!