Can you use a standard ceramic kiln to melt bronze for casting?

Question

I'm starting a home foundry, based in the UK to make small metal casts in aluminium and bronze - practicing with aluminium and moving on to bronze once I've got the skills and equipment set up right.

I am looking at building a furnace using the standard metal drum and refractory cement method but also wondering if the following sort of unit could be used to melt bronze to pour?

It goes to the right temperature, and can be carefully controlled and run on household power so it would work well I think.
The sorts of reasons I can think of that it might not work:

• opening the kiln at the top temp of around 1000 °C could damage it in some way?
• it goes to the right temperature but can't stay that hot for very long?
• it goes to the right temperature but won't open at top temp as a safety feature?
• it costs too much to run at the that temp for long enough?
• there is some sort of reaction with the metal and the materials of the kiln manufacture?
• the construction (firebricks, metal shell, element) is not sturdy enough to stand up to casting temperatures?
• if the kiln does not have ventilation for the fumes?

If not used for melting the metal, I would still probably need to open it at a high temp when taking out ceramic shells after they have been preheated in a kiln like this prior to pouring in the metal.

Anyone who has any information, links or experience would be very much appreciated!

Answer 1

"Could it be used" is a different question than "would it be effective for the task". The question bullets a number of concerns about why it might not work, at least without potentially damaging the kiln. I'm not familiar enough with that equipment to address what safety interlocks it might have or the potential for damage. If those were not relevant concerns, you could use it to melt metal, but this is really the wrong tool for the job. It would not be an effective tool to rely on for this purpose.

Firing ceramics requires accurate temperatures and slow temperature changes, which is what the kiln is designed to provide. A kiln like this uses radiant heat. It could eventually melt the metal, but it would take forever. You not only need to raise the temperature of the metal past its melting point, you need to add substantial energy to change its state from a solid to a liquid. If this was the only tool available, you had a one-time task, and no time constraints, this might let you do it. But it wouldn't be practical to build a process around for repeated applications.

Melting a pourable amount of metal requires transferring a lot of heat. Furnaces for melting metal focus on exceeding the melt temperature as much and as fast as possible. They do this by methods that are much more efficient at transferring energy than radiant heating, such as immersing the crucible in a flame vortex to use convection, or have it in direct contact with the heat source, or use something like induction heating to create the heat directly in the metal.

I'm reminded of an earlier question, Can someone tell me the purpose of this multi-tool?, about a wallet-sized card containing an assortment of punch-out emergency survival tools. None of the tools on the card could compete with a purpose-made tool for a given job. In a survival situation, you could use them if you had to, but nobody would use them routinely as their normal tool.

Answer 2

One answer to a question you did not ask; You will need a minimum of 4000 watts of power to have any hope of melting bronze . Much more power would be much better. The point is that it is not worth going further unless you have the necessary power.