search  current discussion  categories  glazes - ash 

ash glazes at cone 6 oxidation

updated sun 28 oct 01


Bobbruch1@AOL.COM on sat 27 oct 01

<<<<<<Could you tell us what clay bodies and glazes you were using?

Claybody is Standard Ceramic from Pittsburgh, # 420 sculpture body. A "white"
stoneware, bisques white, fires to a fairly light tannish color, which can
darken some as you go over cone 6. Lots of grog. I have found that by
scraping this body once the piece is leather hard, you get a rougher surface
that works well with ash glazes - and probably would work with glazes that
pool. Standard will ship without charging a shipping fee, at least that is
the case with Ohio Ceramics which is about 2 1/2 hours away. The box lists
it as cone 2 to 6. I often fire with 6 down and haven't had a problem, at
least with the claybody. Some of the more "drippy" ash glazes will tend to
move abit more than at 5/6. Again, using softbrick as a base when going even
slightly above recommended temperatures is advisable, although it does create
an issue for space in the kiln. Speaking from experience, you are likely to
be very unhappy if you don't. Even with that and flint on the surface of the
brick, be prepared to use a dremmel with an extra hard bit on the bottoms, or
perhaps a grinder which I don't have, so I can't comment on whether that
would be as effective.

As for the glazes, I'll have to check at the studio, as I have a numerical
system there that isn't on my computer, and I only know the glazes by the
numbers that I have given them.

As for the ash itself, someone had mentioned purchasing ash. I guess I am not
very scientific, but I just asked a friend if I could clean out their
fireplace. They were thrilled to have a clean fireplace, and I got a large
container of ash. Caveat, use gloves and a mask, as most (all?) woodash
contains lye and I believe that particle size also is an issue. Needs to be
sieved before being used in the glaze. While most glaze formulas call for
unwashed ash, I remember getting slightly different results in a reduction
atmosphere between the two, but I don't have any experience in oxidation
using washed ash.

Bob Bruch