Arnold Howard on tue 19 aug 03
looking for potter contact
Patti, what are the bending results of your witness cones?
Where do you place them?
Sincerely,
Arnold Howard
Paragon Industries, L.P.
arnoldhoward@att.net
From: Patti
My disappointment is that the glaze is more matt than I
> wanted it to be. I fire cone 6 in an electric kiln. Often I get the
same
> glaze to be more matt in the bottom of the kiln and shinier at the
top. I
> have used witness cones and the temperature is pretty close to the
same top
> and bottom.
Arnold Howard on tue 26 aug 03
looking for potter contact
From: Patti
> I put 1 set of cones at the top peep and one at the bottom. They both
show
> cone 5 laying flat, cone 6 is a perfect end point and cone 7 is at
about 2
> oclock. As I unloaded the rest of this particular kiln load, the top
shelf
> was the only one that was particlarly matt. It probably was loaded
too
> high with plates and never got to temp. But I always have the problem
of a
> couple of my glazes being too matt if they are loaded on the bottom
couple
> of shelves. I fire with the top peep out for the entire firing and
then
> put it in as soon as I can after the kiln sitter trips. Any
suggestions?.
Patti, I suggest scattering several self-supporting cone 6's on each
shelf the next time you fire. This will show you exactly where the kiln
remains cool.
To increase the temperature of a particular area of the kiln, reduce the
thermal mass in that area. The more thermal mass, the lower the
temperature, because the clay absorbs energy. You can compensate for
cold spots in the kiln by the way you load the ware.
If your elements are the same wattage throughout the kiln, the top and
bottom of the kiln will remain cooler than the center section. (A wiring
diagram may indicate if the kiln uses separate types of elements for the
center section and top and bottom section. Also, the kiln manufacturer's
parts list will give this information.)
The top and bottom of the kiln remain cooler because the top and bottom
elements must heat the lid and bottom of the kiln. These are massive
areas that absorb energy. The center section, on the other hand, has
little brick mass to heat up. So if your elements are the same
temperature throughout the kiln, you should load lighter items in the
top and bottom of the kiln.
If your kiln uses two types of elements--1) center elements, 2)
top/bottom elements--be sure not to mix up the elements when changing
them. Otherwise the kiln's heat distribution will be way off.
Getting a downdraft kiln vent would also help your firings.
Good luck!
Sincerely,
Arnold Howard
Paragon Industries, L.P.
arnoldhoward@att.net
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