Andrew Buck on wed 1 dec 99
After reading the "home made stilts" thread, I would like to offer an
observation to the list. I fire to cone 10 in a gas fueled kiln and use a
very runny rutile glaze on most of my pots. I like the glaze enough to
deal with the attendant problems. When I have a larger pot that has to
sit across the seam between two shelves I usually set it on a round shelf
that is itself set on small balls of kiln wadding (50-50 silica and
kaolin). The reason I do this is because my regular kiln shelves are not
exactly the same thickness and usually are slightly warped in different
directions. If I fire them without the round shelf my pots tend to take
on a slight, but annoying, wobble when set on a flat surface. On the
occasion of one firing, though, I had more large pots than round shelves.
I wanted to get one more of these larger pots in. So, I put the small
balls of kiln wadding directly under the foot of the pot. It should, and
did, act just like putting the pot on stilts. The firing went as normal
and when I opened the kiln all of the big pots were fine except the one
directly on the balls of kiln wadding. On that one pot the glaze ran all
over the place. OH, MAAAANNNN.
What I think happened is that the 1 inch thick kiln shelves heat up much
slower and ultimately do not reach the temperature that my 3/16th inch
thick pots do. The shelves must act as a heat sink to keep the bottoms of
my pots somewhat cooler than the rest. This in turn must keep the glaze
just enough cooler on the bottom, most of the time, so that it does not
run across the bare foot and onto the shelf. By lifting the pot above the
shelf and removing the heat sink, the glaze did not slow down enough at
the bottom of the pot to stay put.
If you use a non-runny glaze, this might not be a problem. I you are
using a runny glaze, and you want to try stilting your ware, be prepared
to change your firing temperature, glazing methods, or foot design to
control the drips.
Just my observations and conclusions there from. Comments to the list
Port Orchard, Washington