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Tips for Fellow Potters

Recipe For Firing Pedestals (Don't use for Making Pots)

Like most crystalline glazes, many overlapping glazes will be fluid when the right temperature is reached and some parts of this “run” will contain unique and often unpredictable effects, some amorphous, some crystalline, some clear or opaque, somewhat like miniature landscapes. Almost all of the glazes I use are “fluid”, that is when they are fired to maturity they will creep down the side of a pot, often partly pooling at the bottom, more so when more than one glaze is used, so like most crystalline potters I make a “firing pedestal” for each piece to collect the overflow, then remove that pedestal after unloading the kiln and grind the foot clean. Videos of making these pedestals can be found on YouTube. I recommend the following recipe for making your own clay for pedestals, or something like it (the important part is use lots of silica, no flux and enough refractory plastic clay to throw well, the more silica the better.):

 

Ball Clay or Kaolin........................................................50%

silica (200 mesh)............................................................50%

Sodium Bentonite (optional)..........................................plus 1% to 2%

 

 

Mix well into a thick slurry and dry out on plaster bats. Mix the bentonite first, very well in water, if you use it, then add the clay, then the silica, mixing well between each addition. This formula, or something like it works well because even when high-fired it is soft, fragile, brittle, and has an extremely high coefficient of expansion due to the high crystalline silica content, and and for these reasons will usually just break away from the foot of your pot and not crack the pot itself or chip the foot when the kiln cools off. Test this first with YOUR clay and glaze, because it may not work for all.

 

It is obviously a very poor choice for actually making pottery, so mark it clearly and use it only for pedestals. Grind the pedestal and the foot flat before or after bisque fire and glue the two together with a paste of aluminum hydrate carpenter's glue, about 5% kaolin, maybe .25% bentonite and some cmc gum. They can also be used as “handles” when glazing and loading the kiln. If anyone tries this I would appreciate any feedback how it works for others.  Comment below.


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