I've Been making 1g globules of gold from a 24 carat bar. I cut 1g from the bar then melt it with a butane torch on a stainless steel plate. The problem is some of the globules are discoloured on top where the flame hits the metal, but the under side remains ok. Why is this and how do I rectify it?
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Bullion.Forum
Non-Chemical Gold tarnish problem
- Thread starter mr-fixit
- Start date
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In addition to the above post.
If I turn the globule over so that the tarnished side faces down and the normal side faces up then re-melt, the tarnished side goes back to the top where the flame is and the underside is normal. There must be a simple answer.
If I turn the globule over so that the tarnished side faces down and the normal side faces up then re-melt, the tarnished side goes back to the top where the flame is and the underside is normal. There must be a simple answer.
You've contaminated the gold with iron, etc., from the stainless. Gold alloys readily with iron. The discoloration on the top surface is oxidation of part of those contaminating metals. The top surface is exposed to the air and/or oxygen from the torch. If you used a reducing flame, you might not see the contamination but it would still be there.
jimdoc
Well-known member
A melting dish.
http://www.contenti.com/products/casting/170-710.html
Jim
http://www.contenti.com/products/casting/170-710.html
Jim
mr-fixit said:
Fireclay, clay/graphite, silicon carbide crucibles. Any of the jeweler's melting dishes. Soft firebrick that has had an indentation scooped out with a spoon. NO metal!
TXWolfie said:
As goldsilverpro stated the gold was contaminated by something not gold. From reading many posts on this forum you will probably need too drop it in acid to pull the gold, then drop it out of the solution, remelt in a clay crucible. My previous statement, please excuse what I typed. I was in the middle of a conversation and what my fingers typed was not being said in my brain to type (brainfart). There is alot of posts on how-to's you just have to find one and go step by step. Since I am fairly new to this and reading alot and watching video's this is what I would believe is needed to be done, but there could be an easier way. Hang in there and there might be an answer from a more knowlegeable person. Just trying to help out on the forums.
Rich
Geo
Well-known member
exactly, dissolve the contaminated gold and re-refine it if you are concerned with purity. borax in addition to a form of lubricant for you crucible/melting dish is also for removing surface impurities that may occur from a dirty torch tip or carbon from the fuel like acetylene will cause.
Geo
Well-known member
sorry. the discoloration you see is just the reaction of oxygen on the surface of the metal. the contamination is all the way through the piece. melted gold will alloy with almost any metal and acts like a solvent so when the melted gold touched the steel it pulled the steel into the matrix.
jimdoc
Well-known member
Mr-fixit,
Why are you creating these little 1 gram globules?
Are you making them from a marked 24K bar?
Jim
Why are you creating these little 1 gram globules?
Are you making them from a marked 24K bar?
Jim
Yes Jimdoc he is cutting 1g from a bar and melting it on stainless steel.
Yes as long as the gold was melted on anything metal it will always have that metal in the Au. The gold acts like a sponge and pulls it in to the mix. Like said before ya wanna get rid of it ya have to reprocess it and melt it on Fireclay, clay/graphite, silicon graphite crucibles. Any of the jeweler's melting dishes. Soft firebrick that has had an indentation scooped out with a spoon. NO metal!
mr-fixit said:
Yes as long as the gold was melted on anything metal it will always have that metal in the Au. The gold acts like a sponge and pulls it in to the mix. Like said before ya wanna get rid of it ya have to reprocess it and melt it on Fireclay, clay/graphite, silicon graphite crucibles. Any of the jeweler's melting dishes. Soft firebrick that has had an indentation scooped out with a spoon. NO metal!
