Duff bogen on sat 8 dec 07
Robert
". The mechanical strength is provided
by the calcium alumina cement as opposed to ceramic fusion."
The Ca and other fluxes in the dug klay and sawdust will also form a melt.
The mechanical strength vis. temperature on a graph would follow a "U" shape. High in the early lower temperatures, low in a nether zone in the middle, and high again as the ceramic bond forms. (cardew has more on this in pioneer Pottery)
" So in a general or specific way" given the unknowns of the dug materials the general "theory" would be increase the melt to disolve SiO2. The weakest phase is in th emiddle so you want to move out of the valley by increasing flux or firing temperature.
In practice testing a series of mixes to failure and backing off seems like the way to go. Could you put together a few soft brick and a "blow torch" and increase your testing rate?-{2brix flat on bottom, 4brix on edge in a spiral, 2brix on top + propane weed burner or?= kiln?"}
" c) proportion of calcined materials." I've lost track of the reason to calcine- clay too plastic? to develope mullite?
Duff
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