# Cupellation in Fusion furnace



## BerrieB (Mar 19, 2015)

Hi There,

For a standard gold fire assay, can you carry out cupellation in a fusion furnace? My cupellation furnace has broken down. Apart from the temperatures, which I've brought down to 950, I thought that one is supposed to be creating an oxidising environment and that the fusion furnace environment is reducing? I.e. can you get proper airflow and proper oxidising conditions in a fusion furnace? How will this affect the cupellation process and what should i look out for?

Thanks in advance.

Berrie


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## 4metals (Mar 19, 2015)

I have used the same furnace for both. I typically use an electric furnace made by Vncella Kilns. The kiln has a small 1" round hole in the top center which I cover for fusions and uncover for cupellations. 

The oxidizing conditions can be met by slightly cracking the door open to drive the lead. When running cupellations, I like to place a row of dummy cupels along the front of the oven and place the cupels I am using for samples behind the dummy row. This seems to protect the temperature and prevents the cupellation from freezing.


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## BerrieB (Mar 19, 2015)

Cheers 4metals, that makes sense, appreciate your quick reply. Being new to the forum and not that experienced, i thought i'd get into trouble given the rules!


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## 4metals (Mar 20, 2015)

Not all of the dogs here bite!


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## goldsilverpro (Mar 20, 2015)

BerrieB said:


> Hi There,
> 
> For a standard gold fire assay, can you carry out cupellation in a fusion furnace? My cupellation furnace has broken down. Apart from the temperatures, which I've brought down to 950, I thought that one is supposed to be creating an oxidising environment and that the fusion furnace environment is reducing? I.e. can you get proper airflow and proper oxidising conditions in a fusion furnace? How will this affect the cupellation process and what should i look out for?
> 
> ...


Is the fusion furnace gas or electric? If electric, no problem. If gas, you really need a muffle to prevent the flame from contacting the lead. I once tried cupelling in an old Johnson gas furnace (#142, I think) that had a flat open hearthplate instead of an enclosed muffle. The flame was fairly high pressure and wrapped over the top of the hearthplate. This blew the molten lead out of some of the cupels, which contaminated the other samples and burned a bunch of small holes in the hearthplate. I solved this by putting firebricks, on edge, on both sides of the hearthplate, thus blocking the flame from directly contacting the cupels. Worked fine after making a few adjustments.


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## BerrieB (Mar 22, 2015)

Hmm, good point. 

It's a diesel furnace (two fan-forced burners at the back) but the burners are mounted quite high up the back of the furnace and i dont think they are powerful enough to cause what you're talking about. The furnace is an Assay & Furnace 50/84 Place Fusion Furnace Diesel - FAS-120-OIL.

Thanks for helping.


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