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kemp 17 crawling/vitreous clay

updated mon 3 nov 97

 

Roeder on sun 2 nov 97

Peggy,

Regarding your comment,>>do others use a cone 10 and glaze fire to ^6
and sell as vitrified work?>> I think you have to take a look at the
commercial clay bodies available out there, the "wide firing range" at
which they are marketed, and consider their percentage of absorbtion.

Just grabbing a handy A.R.T. catalog... the percentages of absorbtion
for a midrange brown stoneware 10.0% at cone 7, red earthenware 9.0% at
cone 06, and midrange whiteware 7.0 at cone 6. The porcelain is 1.3% at
cone 7.

Surely these cannot all be vitreous. Should they be used?
Should a red earthenware, which can be fired to perhaps cone 3 without
deforming, never be used with a cone 06 glaze? What about the "cone
5-10 stoneware"....it will not be vitreous at all cones within the
stated range, will it?

You need a good layer of glass (glaze) lining the portion of a pot that
is intended for functional use. No crazing, pinholes, crawling, etc.
Can't have an unglazed area on the usable surface of a pot. Glaze fit,
durability, toxicity....all are important, especially on a more open
clay body...and getting a good fit is more of a challenge....(or is it
an impossible task?)

Are people using clays that are not vitreous or that have a higher
percentage of absorbtion than, say 1.0 an Irresponsible Bunch?


Candice Roeder
CRoeder@worldnet.att.net
in cloudy Michigan