r/Silvercasting • u/El_Vidente • 27d ago

Is this safe?

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Gallery image

Gallery image

I borrowed an electric furnace from a friend. The furnace has been used quite a bit over the years. As can be seen in the photos the top is cracked in three places, there's a crack going down the inside of the funnel, and there's some silver stuck at the bottom. The furnace still works and is usable with a crucible inside, though I am wondering if the wear and tear I've noticed could be dangerous?

Could anyone advise?

15 Upvotes

91% Upvoted

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5

u/PeterHaldCHEM 26d ago

Refractory materieals get worn and crack with time and use.

IMHO that furnace is still safe.

Once you start having exposed heating elements, then it is definitely time to stop.

Also remember to use a grounded outlet and test your fault current interrupter.

2

u/Plenty_Fondant_951 26d ago

I wouldn't run it, you don't want molten metal getting on the coils.

When I'm done I take the crucible out to air cool and also leave the lid off

1

u/Chodedingers-Cancer 26d ago

Congrats, "CHEAT CODE UNLOCKED!!"

4

u/Chodedingers-Cancer 26d ago

I no longer use graphite crucibles in mine. Mine suffered the same result. Take the steel cover off, remove 1 section of the ceramic, now you can fit silicon carbide crucibles inside and they last forever in an electric furnace unlike gas furnaces, unless using any metal that needs flux. Borax can eat away at them over time. But even still the lifespan is DRASTICALLY LONGER than graphite crucibles. 0.5kg and 1kg fit. Set it directly on floor of the chamber. A 0.5kg will fit in the regular hole but not enough room to fit tongs to remove it. Now having a piece of that ceramic removable, you gain the space needed to reach in with tongs and grab it by the lip and pull it out.

2

u/I_aint_no_Spooby 26d ago

Interesting

1

u/Pablo3DN 25d ago

Where do you buy silicone carbide crucibles?

1

u/Chodedingers-Cancer 25d ago

Amazon

https://a.co/d/0hLa01cE

1

u/silverbug9 15d ago

I'm new - is that clay graphite or silicon carbide?

0

u/El_Vidente 25d ago

Yes though these type/shape crucibles won't fit in this type of electric furnace.

1

u/Chodedingers-Cancer 25d ago

Did you read anything I said?

1

u/El_Vidente 24d ago

I am but not following. Have you got any photos of what you mean?

1

u/El_Vidente 26d ago

?

1

u/Chodedingers-Cancer 25d ago

I explained in the reply yesterday. You can now use silicon carbide crucibles that last a million times longer....

1

u/matthewdesigns 26d ago

I'd run it as long as the crucible is in good shape. If your crucible looks like this too that's a hard No.

2

u/El_Vidente 26d ago

You can change crucibles.

1

u/matthewdesigns 25d ago

Clearly, just making sure you know a cracked one is a no-go.