# Furnace



## sena (Jul 2, 2012)

Hi good day.
I got my new furnace its tilting furnace 20 kg capacity oil fired , so i went on trial run , i melted incernated powder of the xray flim sludge and equal volume of borax, the melt was easy ,when i tilted the pot and got poured to the mould , which was an 
iron cast one , applied thin layer of engine oil over it , the problem is i got some balls struck with the borax which is dark black
is it problem with the mould or with the flux ? iam trying to figure out using cone mould , could i use earthen plant pot thats conical one i couldnt get larger one here in my place,please suggest 
Thanks 
Regards
Sena


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## publius (Jul 2, 2012)

Some of the black may be carbon from ashing the film or from the oil on the mold.

A dip in some dilute sulfuric acid will remove most of the flux. So will striking it with a hammer (messy and you may lose some value as some of the silver may be in little balls).

You may not have poured it when it was hot enough. Most metals are poured when "super-heated", in other words several degrees hotter than their melting point.

Another old founders trick is to put some sodium carbonate (soda ash) on top of the melt just before pouring. It should thicken the flux (slag) where you then can take a rod (steel or carbon) and roll the flux on it like a glass maker's boule. This means there is less flux on your ingot.


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## FrugalRefiner (Jul 2, 2012)

I wouldn't recommend using a steel rod to stir molten metals. The steel will begin to dissolve into the melt and contaminate your refined metal. The carbon / graphite rod is preferable.

Dave


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## goldenchild (Jul 2, 2012)

Add the sodium carbonate as publius suggested. Then quench the bar as soon as it has solidified 100%. This will get rid of some of the flux. Then heat the bar in dilute sulfuric as publius suggested. Anything left over unfortunately will have to be removed mechanically and can be a real pain in the hind quarters. Nice new toy you got there 8)


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## publius (Jul 2, 2012)

FrugalRefiner said:


> I wouldn't recommend using a steel rod to stir molten metals. The steel will begin to dissolve into the melt and contaminate your refined metal. The carbon / graphite rod is preferable.
> 
> Dave



Dave,
I meant to gather the slag/flux as the cool rod (metal or carbon), not to stir the melt. Stirring the melt with thickened slag will cause inclusions as well as contamination.
Robert


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## Palladium (Jul 2, 2012)

I've used oil fired furnaces to sweat aluminum before and i'm wondering what effect or contaminates it might have in it that would affect your metal purity. Just a thought!


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## FrugalRefiner (Jul 2, 2012)

publius said:


> Dave,
> I meant to gather the slag/flux as the cool rod (metal or carbon), not to stir the melt. Stirring the melt with thickened slag will cause inclusions as well as contamination.
> Robert


Robert,
Thanks for clarifying that! I didn't fully understand your post. Your technique is more advanced than mine. Thanks for sharing that.
Dave


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## publius (Jul 2, 2012)

FrugalRefiner said:


> Robert,
> Thanks for clarifying that! I didn't fully understand your post. Your technique is more advanced than mine. Thanks for sharing that.
> Dave


I have spent more time watching others... :mrgreen:


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## Oz (Jul 5, 2012)

I too use dilute sulfuric acid to clean flux off of silver anodes and fine silver bars. Sometimes I use heat to expitite the process. Please note however that silver will go into solution with sulfuric acid. You should check your waste sulfuric acid solutions for silver by cementation on copper.


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