Alex Solla on mon 5 jun 06
A while back I called Dave to get his thoughts on some weird pinholing in our glazes we had never had before. Always the scholar we walked through the causes of pinholing... glaze viscosity, hardness of bisque, dust, and we finally figured it out to be the bisque simply needed to be washed. We had always washed our bisque until about a year ago, when someone on clayart made a comment about it being unnecessary. Hmmm. There's that old adage about your mileage may vary.
Suffice to say, I have yet to give Dave the THANKS he deserves. THANK YOU DAVE F!!!! Havent had a pinhole in weeks!!!! For folks out there who have seen our glazes, you know that a random pinhole here or there that would be okay for some just wont work at all on our pots. www.coldspringsstudio.com
So, we are back to being pinhole-less again! All because Dave F reminded me of a simple part of the big process.
cheers,
Alex Solla
Cold Springs Studio Pottery
4088 Cold Springs Road
Trumansburg, NY 14886
607-387-4042 voice/fax
www.coldspringsstudio.com
Dave Finkelnburg wrote: Gene, and others interested in this,
Washing bisque-fired ware to remove dust and
prevent crawling also has another benefit. As Randy
McCall pointed out, pinholing can be reduced. Here's
why.
The kaolin particles in clay are dehydrated in
bisque firing. As a result, the surface of the kaolin
becomes hydrophobic, thus difficult to wet. When you
wash or sponge the bisque you rehydrate the clay
surface, making it hydrophylic again. Thus when you
glaze, the glaze readily wets the ware and you tend
not to have air bubbles trapped betweeen the ware
surface and glaze.
If you leave the bisque sit long enough in moist
air it will rehydrate on its own. Trouble is, in most
studios it also collects dust that can cause crawling.
:-(
In my experience, porcelain seems to benefit a lot
from a good washing. Whether you glaze the ware after
it is fully dry again or while it is still damp is, in
my experience, less critical than the washing step.
Remember, your mileage may vary, etc, etc, etc...
Dave Finkelnburg
--- Mud Duck Pottery wrote:
> Just curious as to how many of you wash your bisque
> before glazing.
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