ken on sun 2 dec 01
i am new to stoneware ^6 electric. and have lots of questions:
i would like to glaze ad refire a few pots which were previously
unglazed. they have been fired to maturity, but stll absorbant enough
to hold glaze...barely. should this work?
i have a clear glaze which has crazed...it cooled too fast...burnt out
element. i should be able to fire again, and if i cool properly, than
the glaze can be repaired?
thanks in advance...yall's experience has helped me very much, as i am
"teaching myself"...and hate to reinvent the wheel.
peace love
ken in kentucky
Cindy Strnad on sun 2 dec 01
Dear Ken,
You can glaze and refire the previously-fired
pots, however if they are still absorbent enough
to soak up glaze, you should be aware that the
clay does not mature properly at the previous
firing temperature. They may mature during the
second firing, as more heat work will be done, but
then again, they may not. This isn't a problem,
really, as long as the pieces are for decorative
use. If they're for utilitarian use, they could
soak up water during cleaning and use, thus
compromising their integrity (especially in the
microwave).
To make the pieces take up more glaze, you can:
a) Spray the glaze if possible
b) Heat the pots until you can barely handle them
c) Spray the pots with starch or corn syrup and
let dry before glazing
d) Thicken the glaze by skimming off the top layer
of water before stirring. Save the skimmings and
return them to the glaze when you're done.
When you refire, go slowly. The denser fired clay
will not be able to release gasses as easily as
bisque fired clay. Maybe 150F/hr until 500F or so,
then 200F/hr. This is just a guess--you may be
able to go faster, but the above speeds will be
safe.
Your crazed glaze:
You can refire it and probably heal the crazing,
however it will only delay the inevitable. It will
craze again in time. The glaze was either:
a) applied too thickly
or
b) does not fit the clay and needs to be altered
or replaced with a glaze that does fit.
If it is a commercial glaze, you might try adding
silica in 5% increments. That's not the best
solution, but probably the best you can do in that
situation. If it's a home-made glaze, you need to
look into it with a glaze software program to
lower the expansion. If you'll post the recipe,
people will help you with this. Again, when you
refire, do it very slowly. You don't need to
redecorate your kiln in "late pottery shard"
wallpaper.
Since you're just beginning, maybe you haven't
heard of Vince's book, A Studio Potter's Handbook.
You and every other potter should have a copy. Get
it from Steven Branfman at sbranfpots@aol.com .
I'm confident he'll sell it to you at as good a
price as Amazon, and will give you better and
quicker service to boot. Also, I expect Ron and
John's book on ^6 glazes is going to be a real
winner. Pre-order it at
http://www.masteringglazes.com . Good luck with
your new avocation--hope to see more of you.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com
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