Question: preparing my crucible for silver

quick question, or confirmation rather. Before I melt silver in my new
crucible (composition is fused silica with clay bond) I need to prepare it
by heating and coating with borax, correct? I am told to heat it and then
add a couple tablespoons of borax and tip it to work it around and coat the
entire inside.
Just wanting to verify.
Thanks,
- Ben
Reply to
Ben
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Yep, that will do it. I use a carbon arc gouging rod to stir the molten silver as well. The crap will float to the top if you add enough borax to coat the whole top surface of the molten silver
Reply to
Gerry
Thanks Gerry. I actually couldn't wait for the confirmation but did (basically) what you described. I was expecting the borax to liquefy on contact with the hot crucible but instead it just popped and expanded with some at the bottom sticking. The furnace flame was from underneath and I figured that wasn't doing the trick so then I used a torch flame and that reduced it to black stuff. I couldn't ever get the stuff to form the liquid form I was expecting. It either expanded or outright burned and shrank to nothing. Not using enough?
At any rate I got the inside coated with a combination of borax partially stuck and partially burnt on =) Was anxious for my very first melt so I called that good enough. Turned out fine, once the silver melted and formed a button I guess the action of moving it around over the awful prep job I did...finished it. The crucible has a clean glassy finish on the inside now.
Not sure what I did wrong, too much or not enough heat I suppose. As trivial as this may seem to some I'm pleased to have melted metal for my first time, and without screwing anything up! This project was as simple as turning an ounce bar to casting grain...don't laugh you had your "first" once too!
Thanks for the reply,
- Ben
Reply to
Ben
Sounds like you did nothing wrong. When the borax first heats, physically bound water gets driven out, then some chemically bound water disassociates. THis is the spitting and jumping. Once you get to that point, keep on heating, and the borax will melt. The blackness probably came from too reducing of a flame (not enough oxygen) getting soot on/in the borax.
jk
Reply to
jk
snip-----
You need anhydrous borax. The stuff you're using has water included. Yeah, I know, it's dry---but it has water chemically bonded within. Anhydrous does not, nor does borax glass, neither of which will foam up as you described, and don't blow away with a torch easily.
You using a copper covered stirring rod? You're contaminating your silver if you are. Go to a jewelry supply house, where you can buy pure carbon rods, and larger in diameter, so they don't break easily, and last longer. They oxidize as they're used, so the end gets smaller and smaller.
Harold
Reply to
Harold and Susan Vordos
JK/Harold:
Thanks to both for the reply. Wanted to clarify.
{snip}
I'm using borax from Contenti
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Not sure if this is anhydrous but hopefully it'll do (going to have to).
No I'm using a carbon rod also puchased from Contenti. That part I knew (well guessed correctly). My plan is to prevent any foriegn metal from even touching my dish, investment material or anything that could possiby contaminate my precious (lord of the rings lol). Might be too cautious but I'd rather be safe then sorry.
Thanks for the heads up and advice, much appreciated.
- Ben
Reply to
Ben
That is probably not anhydrous borax. If it is a white fluffy powder, it isn't! You can turn your regular borax into anhydrous, but it will turn back overtime if exposed to the air. [Where I live now, I swear it might take only a few seconds:)]
As you heat it up, your regular borax turns into anhydrous borax as it melts. You MAY see two liquid stages. The first is where the borax dissolves in the moisture being driven out of the borax below it, then it will dry out and turn back to a white sludge, which will then melt. If you let this cool it will turn into a greenish glass. THis is what presently coats your crucible. If you grind this up into a grit or powder, you have anhydrous borax, which as harold says, will not blow away as easily as the plain stuff.
OTOH there is no need to waste your money on small jars of regular borax. THe 20 Mule team stuff in the box from the grocery or drug store, is the same stuff, at lower cost. [20 mule team borax that is, not any other product from them].
jk
Reply to
jk

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