Melt dish destroyed.

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marethyu

Member
Joined
Jun 9, 2018
Messages
16
I bought a melt dish online to melt down some gold powder and after my second melt the bottom of the dish where the button and flux pooled became porous to the point where bits of gold would fall into the pits in the base of the dish. I put a filter paper that had minor amounts of copper and probably zinc salts soaked into it with the gold powder and I'm not sure what would have damaged the melt dish. I've heard people say not to use sodium carbonate in the melt dishes so I was thinking maybe the carbonates from the burnt up filter paper may have had an effect? Does anyone know why this happened?
 
No, it isn't graphite. It says it's ceramic in the description I believe it is a fused silica dish.
 
marethyu said:
I bought a melt dish online to melt down some gold powder and after my second melt the bottom of the dish where the button and flux pooled became porous to the point where bits of gold would fall into the pits in the base of the dish. I put a filter paper that had minor amounts of copper and probably zinc salts soaked into it with the gold powder and I'm not sure what would have damaged the melt dish. I've heard people say not to use sodium carbonate in the melt dishes so I was thinking maybe the carbonates from the burnt up filter paper may have had an effect? Does anyone know why this happened?
Click to expand...


Per the underlined - what did you use as your flux ?


Kurt
 
I've attached an image of the crucible, as you can see the sides of the crucible are still smooth but the bottom of the crucible is very pitted.
 

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I don't think so, I didn't even get the gold hot enough to fully melt, just hot enough to fuse together. I was just using a naturally aspirated mapp gas torch and only got the crucible to a cherry red.
 
If that dish was only used twice to melt refined gold powder it shouldn't be so dirty looking. I have a ceramic dish that has had over 20 oz of gold melted in it and it doesn't look anything like that. I glazed the dish with borax when it was new and that was it, never needed any more. Are you sure the gold is pure?
 
He said;

"I put a filter paper that had minor amounts of copper and probably zinc salts soaked into it with the gold powder and I'm not sure what would have damaged the melt dish."
 
IdahoMole said:
If that dish was only used twice to melt refined gold powder it shouldn't be so dirty looking. I have a ceramic dish that has had over 20 oz of gold melted in it and it doesn't look anything like that. I glazed the dish with borax when it was new and that was it, never needed any more. Are you sure the gold is pure?
Click to expand...

Actually it would mate. If it's been used with really dirty gold.
 
marethyu said:
I've attached an image of the crucible, as you can see the sides of the crucible are still smooth but the bottom of the crucible is very pitted.
Click to expand...

It's not pitted. What you see as pitted is a load of impurities in there.
 
marethyu said:
I bought a melt dish online to melt down some gold powder and after my second melt the bottom of the dish where the button and flux pooled became porous to the point where bits of gold would fall into the pits in the base of the dish. I put a filter paper that had minor amounts of copper and probably zinc salts soaked into it with the gold powder and I'm not sure what would have damaged the melt dish. I've heard people say not to use sodium carbonate in the melt dishes so I was thinking maybe the carbonates from the burnt up filter paper may have had an effect? Does anyone know why this happened?
Click to expand...

You can save the dish by boiling it tap water with just a few ml of sulphuric acid. Kinda like what we use to clean up our gold buttons after melting to get extra borax off it. Same principle. Just don't add the sulphuric acid while it's hot, just a few ml into the vessel you're boiling the dish in
 
Hi
Did you glaze your dish with borax before using it? I only ask because I too have a dish just like yours
 

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