Robert on fri 14 dec 07
Upon seeing my latest test brick, it is clear to me that for the
quality of brick I am after would require me to convert a significant
proportion of my kaolinite flint fire clay to grog or calcine. While
the brick has adequate structural strength to build a kiln there are, to
me, excessive shrinkage cracks at cone 11. I would be dealing with
crumblies and I'm certain the kiln life would be reduced substantially.
I'm relatively certain that prefiring my raw material to deal with the
shrinkage prior to casting would resolve the issue. However I don't
currently have a kiln to fire grog and am inclined to build the kiln as
is, accepting the shorter life cycle and processing the material with
pots for the next kiln. I am, however, seriously entertaining the idea
of building a temporary kiln for firing grog. Cardew mentions the
necessity, in a pioneer situation, of building a temporary kiln for this
purpose and also "roasting" kaolin for the same. Does any one have any
reference to a simple method of burning grog say to 1800F or 2000F? Are
there any cultural traditions (pre-indusrial) where this has been
practiced? Could I just mix in an appropriate amount of coal/charcoal
and light the heap? The material is already at grog size, 1/4" to fines
so there will be no post firing crushing involved and the material has
certain limitations/requirements for containment in a firing. Thanks
for any input.
Robert
P.S. I know I could just go buy grog, but I have a longterm personal
commitment to utilizing local resources. Having access to this
material is one of the most unique situations I've had on that path. I
am committed to learning to use this material in the simplest way
possible with the long term vision of localized industry and in
particular several of the blacksmiths, glassworkers and potters that I
know in the area.
It's quite a thing to be able to borrow a pickup and drive up the
mountain and haul off your kiln, batch furnace, forge, smelting furnace.....
Take care
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