Ian Currie on wed 7 mar 01
Greetings
This is great advice from Bill. I like to go a little further. If I am
firing new glazes or using a different firing cycle, I always use draw
trials, as well as lots of cones as Bill suggests. Draw trials are rings or
flat bits of clay, usually glazed, that you can remove with a poker or
tongs. Trouble is of course that many kilns are not built for this. Plus
if your kiln is electric you need to avoid getting electrocuted!!!!
I would NEVER buy a kiln that doesn't facilitate draw trials. My point is
that perhaps it is time to start bringing some pressure to bear on kiln
designers (by consumer choice) to include this essential feature. In my
travels around the US I have noticed a tendency to automate the firing.
Great for my workshops where we want to get some results out overnight! But
not good for the long term quality of our work. We need to be involved with
the firing if at all possible. Sometimes the firing has more effect on the
glaze than dramatic changes to the recipe.
Draw trials enable us to watch the maturing process of the clay and glaze.
They can indicate the stage that a problem is emerging, thereby aiding the
analysis of the cause.
They tell us when to finish the firing, even better than cones. This is
particularly useful if there is any doubt about new glaze materials or
recipes.
They can indicate by comparison with samples left in the kiln whether the
cooling rate is important.
They can show us when certain crystals grow in the cooling cycle.
They can indicate current atmosphere in the kiln. (Use unglazed iron-y clay.
Draw and quench in water, then break and observe the colour of the clay.
Reduction gives grey. The clay must still be porous when drawn.)
However even without any electrocution problem there is an element of
danger. Use appropriate gear and take care! Be aware the samples may
shatter, especially if large and vitrified.
Regards
Ian
http://ian.currie.to/
-----Original Message-----
From: william schran
To: CLAYART@LSV.CERAMICS.ORG
Date: Tuesday, March 06, 2001 6:30 PM
Subject: kiln sitter problems
>To Francie and others who use sitters to fire:
>Save that little metal template that came with the sitter. It's
>necessary to get a good adjustment.
>Now, what you don't want to hear - quit using the sitter to fire the
>kiln. Use the sitter as a back-up. Use witness cones, a pack of
>three, for every firing! For your first few firings, put a cone pack
>on every shelf, at every level to get a good sense of how even/uneven
>the heat is in the kiln. Using witness cones is the only way to
>achieve consistent results.
>Bill
>
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