# How to clean silver from muffle furnace refractory



## snoman701 (Sep 19, 2017)

Any suggestions on how to remove silver from muffle refractory? I can't remember who made the furnace, and it's too hot to maneuver to get to the name badge.

I was excited about this little guy too. 

Some days are best spent sleeping.


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## snoman701 (Sep 19, 2017)

Well, after going from frustrated to problem solving, I figured out that I could heat the furnace up to about 1650, which softened the flux and allowed me to pry the silver up with a screwdriver. I then grabbed on to it with a pair of long handled pliers and gently worked it out. Thankfully, the muffle refractory is still in good condition, less the flux. 

I still have 10 grams of silver missing, and I'm pretty certain it's in one of the vent holes, so that will require taking this thing apart and torching it out. 

i still haven't figured out the dish though. there are no cracks that I can see, so all I can figure is that there is a hole in the bottom. I haven't heated it back up yet to investigate. If that didn't happen, the flux managed to push the silver (chunks, not sponge) out of the dish. 

Or, the neighborhood cat came in the garage and jumped on the furnace while I wasn't there.


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## g_axelsson (Sep 19, 2017)

Steam explosion maybe, a small one?

Göran


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## snoman701 (Sep 19, 2017)

g_axelsson said:


> Steam explosion maybe, a small one?
> 
> Göran



Maybe?

...now that I remember more, I looked in there and it was all melted, but still hadn't glossed over. The melt still looked like swiss cheese. That was around 1800. I would imagine a steam explosion at that temperature would be more violent. 

I know there is pitting in the melting dish. I think these ones are Chinese, and I've never had them develop this much pitting so quickly.


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## nickvc (Sep 20, 2017)

One of my best buys was a small second hand swirl furnace that needed new lining, it was probably around 1.5 gallon size, I stripped out the old lining and recovered several ounces of gold from it :shock:


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## goldandsilver123 (Sep 27, 2017)

Your melting dish was ceramic? 

You were using carbonate in the flux? If so, were it well mixed with the borax?

From my experience, carbonates dig holes in ceramic crucibles, specially if not mixed well with the borax, we have some bad fire assay crucibles that we cannot leave unattended in the muffle or it will spread the flux through the bottom all over the muffle.


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## anachronism (Oct 11, 2017)

Dean always recommends two crucibles one inside another for exactly that reason Sno.

Edit: two of differing materials.


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## snoman701 (Oct 11, 2017)

It's a great idea, but I don't think I could fit two crucibles in there. It's just a little baby chamber...4x4x6 or so. 

I bought it more for heat treating small parts....but figured as long as I've got it. 

Actually, I'll just make an inconel baking pan for it...grand idea! One of the scrap yards I frequent has some perfect little inconel 718 drops that will fold right in to a pan once I trim the corners.


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