claybair on sun 13 oct 02
Jose,
I had the same problem when I was using wax.
I had wax on my fingers even when I thought I had cleaned them off.
The problem stopped when I started using a dense wet 1/4 inch sponge to wipe
the bottoms of my post. You can use other materials to wipe off your feet...
wet towel or rug are 2 that come to mind.
Some other things to check:
Wipe your bisque with a damp sponge to get rid of any dust.
While wiping & as you rotate your pot make sure your fingers are not moving
from a dusty section to an already wiped section.
If your glaze application is very thick and starts to crack when drying you
will get crawling also. I have occasionally circumvented this by carefully
using a wet brush to smooth out the crack. However that is just a lazy
inconsistent solution. The safer way being washing and drying the pot and
glazing again.
If you bisque lower your pots may suck up too much water. On thin pots I
have had problems glazing both sides as the bisque gets saturated with water
and have wait for it to evaporate before glazing the other side. I am much
too impatient for that process even when I force dry it with a torch plus if
the glaze is too thick it will definitely crack and crawl upon firing.
Impatience is my Achilles heel... I have ruined too many pots because of it.
Too impatient to use test tiles and use good pots.
Using Vaseline instead of wax as a resist because I do not want to wait a
day for the wax to thoroughly dry. But I must admit I am getting pretty good
at it.
Opening the kiln a little to soon.
The list is ever growing......
Gayle Bair
Bainbridge Island, WA
http://claybair.com
-----Original Message-----
From:Jose A. Velez
Ladies and Gents:
I have been using a mid range porcelain (cone 4 to 6). I bisque to 06 and
fired with a Gerstley borate based glaze to cone 6. I have used these
glazes successfully on stoneware, but on the porcelain the glaze is fine and
seems to be a good fit, but it leaves some bare spots. I apply the glaze by
dipping and the glaze seems to adhere well, but then it moves during firing
leaving these bare spots. So the glaze is fine except for these bare spots.
The bare spots are not very big (say a quarter to half dollar) and of random
shapes with smooth edges. I thought in the beginning I had touched the
bisqued pot with some masquing wax I use to protect the foot of the vases,
but now I am more inclined to believe 06 might be too high a temperature for
bisque firing this particular porcelain and maybe I need to go to a lower
temperature. The bisqued porcelain appears to be more vitrified than the
stoneware (tighter smoother surface). I have not conducted any tests for
clay/glaze fit, but I do not see any signs that is not a good fit.
Any clues as to what might cause this and possible cures?
Regards, Jose A. Velez
___________________________
Jose A. Velez on sun 13 oct 02
Bonnie and Gayle:
Thank you for your suggestions. I think eliminating the possibilities =
of wax and dust contamination is easy enough and will be the first steps =
I take. Eliminating wax altogether sounds like a good goal. If not, I =
might try lowering the bisque temp., but only after I try the other =
remedies.
Thanks,
Jose A. Velez=20
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