# Re. cleaning borax from graphite melting dish.



## leondavids (Dec 11, 2011)

Hello great forum , been reading more Hoke, she writes about a booklet that refers to the melting of precious metals .I cant find any info about the preparation and cleaning the remaining borax from a graphite melting dish .Did i miss this instruction or can someone point me in the right direction please.

thanks in advance.


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## philddreamer (Dec 11, 2011)

I don't know how to "clean" the borax off a graphite melting dish, but I've cleaned my silica crucible by boiling it in 10% sulphuric.

I buy 40 & 100 dwt by GROBET USA fused silica crucibles. When they got dirty & thick with borax, I boiled one of the 40 dwt to test I find out if it would withstand such procedure. After letting it dry for several days, I started to apply heat & finally melted scrap gold that I was shipping. It's been more than 6 mos. & I've done more that a dozen melts since, with no cracking or problem at all. I just melted scrap gold last tuesday with no problems.

I don't know if you could boil a graphite one. I only use graphite for pouring
my metals or a rod for stiring.

Someone with more expirience will share their knowledge.

Phil


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## leondavids (Dec 11, 2011)

philddreamer said:


> I don't know how to "clean" the borax off a graphite melting dish, but I've cleaned my silica crucible by boiling it in 10% sulphuric.
> 
> I buy 40 & 100 dwt by GROBET USA fused silica crucibles. When they got dirty & thick with borax, I boiled one of the 40 dwt to test I find out if it would withstand such procedure. After letting it dry for several days, I started to apply heat & finally melted scrap gold that I was shipping. It's been more than 6 mos. & I've done more that a dozen melts since, with no cracking or problem at all. I just melted scrap gold last tuesday with no problems.
> 
> ...



Thanks anyway for your input .


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## jimdoc (Dec 11, 2011)

I would switch to fused silica melting dishes like these;
http://www.contenti.com/products/casting/170-710.html
http://www.contenti.com/products/casting/170-712.html
or http://www.ebay.com/itm/FUSED-SILICA-MELTING-DISH-CRUCIBLE-GOLD-SILVER-Set-3-/130423361715?pt=LH_DefaultDomain_0&hash=item1e5dd690b3

Cleaning them has been discussed more than once on the forum.
If you can't find something in Hoke's book, the search button here on the forum should help.

Jim


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## glondor (Dec 11, 2011)

Harold has a great post on how to clean a dish. It is difficult to find however. I think it is in a thread that is not about cleaning dishes. If you search, you may find a link to it in other posts. I meant to book mark it the last time I found it, but did not. If you find it let me know!


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## jimdoc (Dec 11, 2011)

Is it this one?
http://www.ebay.com/itm/FUSED-SILICA-MELTING-DISH-CRUCIBLE-GOLD-SILVER-Set-3-/130423361715?pt=LH_DefaultDomain_0&hash=item1e5dd690b3

or this one?
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=39&t=8498&p=79312&hilit=clean+dish#p79312


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## leondavids (Dec 11, 2011)

glondor said:


> Harold has a great post on how to clean a dish. It is difficult to find however. I think it is in a thread that is not about cleaning dishes. If you search, you may find a link to it in other posts. I meant to book mark it the last time I found it, but did not. If you find it let me know!



Sure , will do so .Thanks.


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## qst42know (Dec 11, 2011)

philddreamer said:


> I don't know how to "clean" the borax off a graphite melting dish, but I've cleaned my silica crucible by boiling it in 10% sulphuric.
> 
> I buy 40 & 100 dwt by GROBET USA fused silica crucibles. When they got dirty & thick with borax, I boiled one of the 40 dwt to test I find out if it would withstand such procedure. After letting it dry for several days, I started to apply heat & finally melted scrap gold that I was shipping. It's been more than 6 mos. & I've done more that a dozen melts since, with no cracking or problem at all. I just melted scrap gold last tuesday with no problems.
> 
> ...



I hope you save the acid you treat your dish with. Have a look at your dish with a loupe. You should see a multitude of microscopic beads of gold.


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## philddreamer (Dec 11, 2011)

Indeed Qst, that was the reason for the process. I could see the tiny gold beads & diamonds & I was after them. So, I figured that if 10% sulphuric dissolves the borax from my ingots, why not from the dish? I had extra melting dishes, so if it didn't work, I could always crush the dish & run thru acids. I'm glad it worked & I can still use it! 

I used plenty of borax, soda ash & heat to recover what was left in the dish when I did the first melt; & some day, when I retire the dish, I'll give it the hammer/acid treatment! :mrgreen: 
I thank you all for sharing your expertice!

Kindly,

Phil


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