Crucible search

[Wanna-Be]

I mentioned to a friend that I was looking for a small, #4, crucible(s). He makes jewelery and melts a some silver. He contacted a vendor who sent him a small(ish) size crucible for approval, but it was too large for his needs and they told him to keep it, rather than pay the return shipping. He just gave it to me today.
I know it is smaller than #4 and measures 3.5"X3.5" outside. It's volume is exactly 1 cup, to the rim. It is a molded but I have no clue of what. It has never been fired in a furnace and has a white wash over all surfaces. I would say it is about a #1, if I were to take a guess.
I can use it for very small pours, if it can stand the heat.
I'm attaching a picture and I hope someone might recognize it and type.

Thanks,
Steve

PS. And what would be the 'first Firing' procedure??

[Harold_V]

I'm pretty sure it isn't a wash.

For years, I processed (refined) precious metals. Typically, volumes are not large enough to warrant melting in a crucible, so melting dishes were employed. The best on the market were sold under the Vigor name, and were made of a white clay, just like your crucible (with which I am familiar). It will be well suited to melting copper alloys (or aluminum), but you must temper it before putting it in service, otherwise it's likely to crack upon the first heating.

To temper the crucible, place it in a warm area, where temperature can slowly be raised above the boiling point of water. It's important that any residual moisture be expelled very slowly. Once it has soaked long enough to have driven out all the moisture, you can improve its ability to pour metals by raising the temperature to a dull red, at which time the entire interior of the crucible should be covered with a light coating of borax. Anhydrous, or borax glass is the easiest to work with, but 5 or 10 mol borax will serve. It's just very light and fluffy and easy to blow away with a torch. Once the added borax is well heated, it should flow out and coat the entire surface of the crucible with a clear, glass-like coating. That will act like a lubricant, allowing the charge to pour easily. As the borax coating discolors from absorbing oxides, it will get sticky, at which time it can be cleaned with soda ash and more fresh borax. That should be poured out after cleaning the crucible, then a new, fresh coating of borax applied.

Take note that soda ash is very aggressive, and will dissolve the surface of your crucible, thinning it in the process. You won't be able to clean it more than a couple times, at which time it will have been compromised enough to render it hazardous to use, due to breakage.

If you intend to melt aluminum, ignore the additon of borax, but in any case, be certain to preheat the crucible, to avoid cracking.

Harold

[Wanna-Be]

Thanks for the very useful information on tempering and glazing this crucible. I expect I will use it for smaller pours of copper or bronze and should perform this glazing procedure.
What is your recommended source for the borax? Would I have to purchase a larger than necessary quantity?

BTW. When I met the fellow that sold me the Mighty-Mite muller, we discussed getting green sand in a place in Tacoma. I forget the name. But I got the sense that they only sold large quantities of sand. Do I need to know someone to get a small quantity, 300-400# maybe??

Thanks
Steve

[Harold_V]

What is your recommended source for the borax? Would I have to purchase a larger than necessary quantity?

I have on hand some anhydrous borax, so I'd gladly donate a quart or so to the cause if you find yourself near Onalaska. It is what remains from my years of refining precious metals. Otherwise, you can buy Boraxo in your local grocery, with some luck. It will serve, but isn't anhydrous, thus it's easy to blow around. If you get the crucible hot enough, it will melt when sprinkled on the surface, but the water combined with the borax tends to cool things rather quickly.

BTW. When I met the fellow that sold me the Mighty-Mite muller, we discussed getting green sand in a place in Tacoma. I forget the name. But I got the sense that they only sold large quantities of sand. Do I need to know someone to get a small quantity, 300-400# maybe??

Sorry, I'm not experienced in buying sand. While I have future need for some, I hope to use olivine, which is somewhat more costly, but better suited to casting iron and steel. Having an induction furnace, that would be the best choice for me.

With a little luck, jpfalt will chime in. He has considerable experience in that regard, and lives in northern Oregon. He may be able to provide some sources.

I expect that buying in small quantities (bagged) will be more expensive than buying in bulk, but there's only so much we can use on a hobby basis.

Please do share what you learn when you inquire. I am not the least bit familiar with sources in Washington, having moved here from Utah. Larsen Foundry Supply, in SLC, sold sand in small lots.

Sorry I'm not more help!

Harold