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Firing Mid Range


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#1 Dee Sota

Dee Sota

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Posted 24 April 2010 - 09:28 AM

Newbee....
I am reading books which has many suggestions about open lid at what Temp for bisque and glaze firing for "mid range clay and glaze"
What is the general rule of thumb. (SKUTT 1027 Kiln)

Bisque cone 06
1 hour lid open on low? Then 2 hour lid open on Med? Turn to high and close?

Glaze cone 5
1 hour lid open on Med? Then 1 hour lid close on Med? Turn to high with lid closed?



ALSO Reading and confused.... Bisque should be DAMP when glazing
Bisque should be DRY when glazing


Any help will be very grateful. It's confusing.... but SO MUCH FUN! Thank you... Dee



#2 Sherman

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Posted 05 May 2010 - 01:11 PM

Newbee....
I am reading books which has many suggestions about open lid at what Temp for bisque and glaze firing for "mid range clay and glaze"
What is the general rule of thumb. (SKUTT 1027 Kiln)

Bisque cone 06
1 hour lid open on low? Then 2 hour lid open on Med? Turn to high and close?

Glaze cone 5
1 hour lid open on Med? Then 1 hour lid close on Med? Turn to high with lid closed?



ALSO Reading and confused.... Bisque should be DAMP when glazing
Bisque should be DRY when glazing


Any help will be very grateful. It's confusing.... but SO MUCH FUN! Thank you... Dee



Dee,

You should never need to prop open a kiln lid. If you need to have access for oxygen to get in during the bisque and for water vapor to escape, simply leave the top peep-hole plug out (I sometimes leave the bottom plug out as well at the beginning of a firing to encourage air flow through the kiln).

Most folks glaze bisque when it's dry, but there is a reason to wet it first: if you have a textured surface, where glaze would have trouble getting into the nooks and crannies (leaving bare spots), then wetting the bisque quickly before glazing will jump start the capillary action that draws water into the body of the pot. This is what draws the solids in the glaze against the body, forming a layer of raw glaze on the outside. Sometimes, especially on textured surfaces, and sometimes with particularly viscous glazes, the glaze layer will begin forming against the body before it gets a chance to contact all those little recessed areas and it forms what looks like an even layer of glaze when, in fact, it has formed a kind of bridge over the small low spots. These show up after the firing as the glaze that does not actually contact the body "crawls" away and shows the bare spot. Wetting the bisque first can sometimes help draw the water in the glaze down into those areas before the layer of solids starts to form.

You may need to extend the time the bisque is dunked in the glaze, though. Since it has already absorbed some water, it will need a slightly longer time in the glaze to build up the same thickness of glaze solids.

Hope this helps.
Sherman Hall
Editor, Ceramics Monthly
Co-host, Ceramic Arts Daily
http://www.ceramicsmonthly.org




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