A seller has 3 of these kilns on ebay:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 96707&rd=1
Large enough for breastplates and room to spare, digital control, and not a bad price. You'd probably want a different one for helms and individual pieces, but if you're willing to deal with top loading, these look good.
Heck, some swords would fit in there if you could fill the extra room. Would filling some space with fire bricks or other resonable material screw up the heat distribution too much to be worth trying?
My apartment isn't up to it, but there may be others here looking to get into heat treating armour.
Jacob
