Suzanne Furman on mon 8 nov 99
Janet Kaiser wrote......
.<< Because the base of a pot undergoes less pressure during throwing and is
worked on less than the walls, it is less aligned in particle structure and
liable to greater shrinkage. Deliberate working on the base or its compression
from the outside later in the throwing can help prevent cracks>>
ClayArter's.........I am an "Oldie" been doing pots for 28 years and was
lucky in the beginning to have some darn good mentors........Never had an S
crack problem so am going to at least tell you how I work with the bottom of
a pot.....it is important because many of the claybodies today are based on
Ball Clays and Fine Grained Fire Clays......compression is very
important......and the most important on the bottom of a pot......I use a
Wooden Rib to compress the bottom of all pots.....You open the form.....get
the water out.....and before bringing up your wall.....compress the bottom
with a rib with a flat side......please remove water from the inside bottom
and really from the outside as well before each pull upwards.....keeping the
bottom from becoming soaked on large vessels is very important....before
completing an open form or before closing a form and making sure first all
excess water is removed......... I compress one more time on the inside
bottom with a sponge on a stick with a piece of shamey over the
sponge.........then when the pot is leather hard I tool and Compress the
bottom....I use a metal old fashioned butter knife but there are wooden tools
made for this purpose....In this fashion....there is a great deal of
compression done to the bottom.....ie no S cracks......One other very
important concept is that you Tool to the INSIDE shape.....this is very
important to have an even walled thickness side and bottom walls.......
tooling is not arbitrary....."gee I like the shape so I will stop here" is
not a pottery technique......an even wall thickness at the bottom of a large
vessel will help with this problem as well.....and of course I am assuming
that everyone is also compressing the side walls after tooling them......I
hope this helps some.....take care everyone......Suzanne Kraman HREF="http://members.aol.com/claymaven/ClayWavesStudio.html">ClayWaves Studio<
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