Looks like the porcelain enamel I was excited about isn’t all that I thought. Shouldda known. Kinda exactly the opposite of what works for roasting a duck is working against me in the drum design. That and that roasting poultry is a pretty much a linear process in terms of input.. coffee roasting isn’t.
Anyway, I have become (somewhat) initiated into the world of coatings. What’s possible and what’s not. What works well and what doesn’t. Which ones distribute heat, which ones are thermal barriers. Porcelain Enamel, contrary to waht I had read, is a barrier, which is why it works to trap heat (and moisture) in that Le Creuset cast iron dutch oven so well.
So I think I have the right formula for coatings that will distribute the heat efficiently and evenly from the flame to the interior of the drum. It will be a bit tricky to make sure that the ambient temperature around the drum stays stable and responsive to the flame, but I think that with a combination of insulation and coated drum material, I will be in really good shape. So that means I am ready to begin building the drum and the housing. Aluminum and mild steel. I never thought that I would end up with a drum that didn’t have stainless steel as the inner surface of the drum, but here I am, with a design for a solid aluminum drum. Well, it’ll be coated of course but the aluminum will transfer the heat from the heat source to the roast chamber extremely well. Extremely quickly. And because of the coatings, it should be extremely even. Now, all I need to do is build the working prototype.
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