I received what is supposedly a silicon carbide crucible and it's leaves a dark black residue when wiped. Similar to what I would expect from a carbon crucible or piece of lead. Is this also expected of silicon carbide? Or is this a fake?

Good Morning,

What part of the rock do you call home?

I would ask the supplier.

Neil

Canada, but this was ordered off Amazon.

Silicon carbide measures 9.5 on the Mohs hardness scale.  This would be one way of verifying it's authenticity.  Do you have some hardness picks or access to some?  Otherwise, if you calculate the density that could also determine what it is.

Silicon carbide (carborundum) contains well, silica and carbon, and is usually sintered together from powder or pressed to shape, so, I wouldn't be overly surprised if it had black powder on it. The carbide itself will usually be black or kinda dark brownish when rubbed depending on the composition when they made it. Silicon carbide is also about half again as heavy as graphite, but if you don't have a graphite crucible to compare it to, that doesn't help much.

Of course, the real problem you have is that many silicon carbide crucibles contain graphite, just as many graphite clay crucibles contain silicon carbide. I dunno, if you use it and it starts coming apart too early, I would lean towards a possible counterfeit...or user error. Or rough handling during shipping. Or the stars are misaligned....

20 hours ago, Toor said:

Canada, but this was ordered off Amazon.

Good Morning Toor,

Canada is a big place, can you be slightly more specific. If you put your area in your avatar, people will then know how to help.  I live in Victoria BC. There are a lot of other association's across Canada, I was asking to help point you to someone closer to you, than on the interweb.

Neil

Have you fired/used it yet. The only sure way to tell that i know of is to use it. It will form a hard outer layer that is grey in color. Nothing black should wipe off after it's first use. Graphite crucible are only good in electric furnaces. If you are using gas/propane the graphite crucible will erode away after just a few uses.

On 4/5/2024 at 9:58 AM, swedefiddle said:

Good Morning Toor,

Canada is a big place, can you be slightly more specific. If you put your area in your avatar, people will then know how to help.  I live in Victoria BC. There are a lot of other association's across Canada, I was asking to help point you to someone closer to you, than on the interweb.

Neil

I'm in Alberta. I haven't used it yet. I'm not really using it for smelting as much as I am using it just as a solder pot on a electric laboratory hot plate so coming apart under temperature isn't really much of a concern. For my purposes, the concerns is more that carbon residue might contaminate the solder.

On 4/4/2024 at 2:46 PM, Nobody Special said:

Silicon carbide (carborundum) contains well, silica and carbon, and is usually sintered together from powder or pressed to shape, so, I wouldn't be overly surprised if it had black powder on it. The carbide itself will usually be black or kinda dark brownish when rubbed depending on the composition when they made it. Silicon carbide is also about half again as heavy as graphite, but if you don't have a graphite crucible to compare it to, that doesn't help much.

Of course, the real problem you have is that many silicon carbide crucibles contain graphite, just as many graphite clay crucibles contain silicon carbide. I dunno, if you use it and it starts coming apart too early, I would lean towards a possible counterfeit...or user error. Or rough handling during shipping. Or the stars are misaligned....

Hmmmm. I was wondering how they were able to form a refractory material like silicon carbide so cheaply but if it's just pressed together with graphite that would explain it.

Good Luck,

Which part of Alberta?  There are quite a few Blacksmiths in Alberta.

Neil

  I would buy a quartz melt dish or something along those line if you're worried about carbon. I use a pretty large one for my silver pours. I'm not sure about a hot plate getting any crucible hot enough to be used in that manner (I maybe wrong). Why not a stainless steel bowl or something that transfer heat better and way cheaper?

Fyi

    If you would have given us more information like your intended use we could of solved this for you day one. I would of told you to buy something like a lee lead hotpot. It has a heating element built into it. Add a rheostat or something to control the temp.