Electric Kiln as a Foundry

John Collier - Wednesday, September 17, 2008 - 6:40pm

Hello all
I am also new here. I am thinking of using an electric kiln as a foundry.
My idea is to make a large cup in the top of a plaster investment . I
would turn the investment up-side-down, bring the heat up to melt the wax
out, then turn it over and start bringing up the temp to burn out the
remaining wax. l would have put ingots in this cup then I had turned it
right-side-up. Then wait for the metal to melt and flow down into the
chamber. Will this work? Also, This will subject the plaster to a long
metal to plaster contact--can it stand this?
Thanks

» John Collier's blog | add new comment

NO

B.J. Severtson - Thursday, September 18, 2008 - 6:58pm

Will this work...Not as described. you need a gate to open to allow the desired quantity of metal to fill the mold.
The molten metal in your cup will not all become fluid at the same time the first of this liquid will go into your sprue freeze there and prevent a complete casting.. If you melt some metal in a crucible you will observe that the largest quantity of molten metal draws the smaller pieces of metal to it. That action will prevent the metal from dropping into your mold. This process sounds similar to steam casting. on a jewelry scale. Their sprue base is cup shaped. and when the desired quantity of metal is puddled in the depression in the flask,a wet pad is pressed over the flask and metal. The resulting steam is supposed to force the metal into the mold. This technique gets my nomination for techniques that should be lost in the annals of history. That said if you have a low enough melting alloy say a Britannia metal and a huge excess of heat it just might work. particularly of what you are wanting to cast resembles a sprue base. All in all there are a lot of ways that do work. But hey It's all fun. nothing wrong with that...Oh wear gloves.. take two a aspirin and keep away from children. enjoy BJ

» reply

Kiln as foundry

visitor - Monday, October 6, 2008 - 4:04pm

Hi BJ
Thanks very much for your answer. Maybe i didn't say this very well . What i am proposing is to bring the whole thing --plaster cup full of bronze , plaster investment, and bronze up to bronze melting temp. In that way the investment should not clog by cooling metal, should it? It is all at 2100 degrees.

» reply

I would disagree with what

Lawrence Parramore - Saturday, October 11, 2008 - 8:16am

I would disagree with what is written above on several points.

I have used 'pressure' casting both Vacuum and Potatoe, My potatoe system beat a $100,000 German casting system every time, less porosity better detail and so on.

I have also seen ceramic shell casting done in a very similar way to what you are thinking, first the sprue base is made as half round and then the whole mould is burnt out, then the required amount of metal with a little flux is put in and another half dome of ceramic is closed over this. the mould is held upside down and the new half dome acts as the crucible, when you are satisfied that the metal is molten you simply invert to do the cast.

I have done the method you were thinking of with glass, the surface does suffer a little in that because the Glass (it is a metal) is in contact with the 'plaster' it comes out with a satin finish.

I think this is one where you could quickly learn from experience, I think you will get a cast, it is the porosity that I think could be a problem, though it wasn't when I did it with glass, also depending on the metal, some would possibly have an adverse reaction to being in contact with the 'plaster' because of the sulphur.

Hope this helps.

» reply

Well how about that.

B.J. Severtson - Sunday, October 12, 2008 - 8:18am

I guess there is only one way to find out. Give it a try. be sure to document your process and keep us posted on your progress. We love pictures.
Notice that I've suggested you invest your time, energy and materials into this hypothetical casting method.
This is what I think is going to happen. The metal will melt as metals do. Smaller pieces and the exterior of the mass first. This small quantity of molten metal will drip into your casting and possibly remain liquid. meanwhile the mass above is gaining heat. At some point the mass above is going to ball up. This process of metal melting should continue happening over and over again until the casting is complete, according to the theory. The theory leaves out several factors. It leaves out oxides forming on the drips of metal in the casting and gasses forming that may prevent the flow of the metal. It further leaves out the failure temp of the investment. So that your (casting) may not only be very porous but contain small bits of investment.
Let's look at this another way. I'm going to suggest that the reason other methods developed is because this proposed method either doesn't work or because it can be easily improved upon. Rather than dealing with the problems of dripping metal, oxides and gases forming. Inverting the molten metal over the invested flask is an African approach centuries old. Just pouring the liquid metal into the mold is a pretty direct method. Heck melting the metal in the flask and then covering it with a potato, to create steam to force the metal into the flask, works. Melting the metal in the flask and then spinning it overhead on the end of a rope, works. Melting the metal over the casting and opening a gate or valve to fill the casting, works. Adding or creating a vacuum in the flask to draw the metal into the casting, works. Of course results vary by technique and per individual. I applaud your question. What happens inside that flask is an interesting study. Which techniques work best can be a life's journey. Good stuff It's my personal decision not to waste a potato to get a casting. I've found better ways to cook a potato, too. But there are others that swear it's the best way. Cool with me.
Best of luck, give it a go. Really doesn't bother me to be proven wrong. I learn stuff everyday. Edison is one of my heroes. Not because he discovered what would make a great filament in a light bulb, but because he discovered hundreds of things that wouldn't. OH wear gloves.. Brad

» reply

B.J. Severtson is right, the

Lawrence Parramore - Sunday, October 12, 2008 - 10:25am

B.J. Severtson is right, the oxide is going to get in the way, there are ways round it, but as B.J. says that is why there are so many methods!

I have a vacuum casting system and would not consider a centrifuge system ever again.

The thing is that there are many ways of achieving the same result, for me I like simplicity many companies make there money by bringing in weird science when really most things are simple.

Wet tissue paper etc can be used instead of potato and this system is quite close to what you were asking I think? in that you do not need to buy other equipment.

My concern would also be will your electric kiln get upto bronze melting temperature satisfactorily.

» reply