Dave Finkelnburg on tue 28 may 02
Michael,
I accept your explanation, but have a question from it. I observe a
similar occurrence. The fuzz is really fine crystals of something, a salt,
I assume. I get the fuzz growing from the plaster slabs on which I dry the
clay slurry made from my clay trimmings and scraps. I do only wheel-thrown
or hand built work with commercial clay, and have no sodium silicate,
Darvan, etc. in my studio. What could the source of the salt be that I am
observing?
Thank you!
Dave Finkelnburg, resting by reading ClayArt while firing the kiln
in Idaho
From: Michael Banks
>If you are using sodium silicate, with or without soda ash, the fuzz is
>usually sodium sulphate.
>
>This soluble salt is produced by sodium silicate reacting with the calcium
>sulphate mould. Capillary action wicks the resulting solution to the
>surface, where evaporation causes the precipitate to form.
>
>Sodium silicate slowly attacks gypsum (plaster) moulds via this process,
but
>organo-sodium products (dispex, darvan) are much less corrosive.
Paul Herman on tue 28 may 02
Dave,
All ground waters and river waters contains some dissolved minerals,
which will concentrate in your plaster bats, with more added each time
you use them to dewater clay. When the pores get sufficiently clogged,
they start to grow fuzz on the edges. I have noticed that by the time
they start to fuzz, then they aren't as quick to absorb moisture.
So your fuzz probably came from the water the clay was made with, from
the clay itsself, and possibly some from the feldspar in the clay mix.
Best wishes,
Hardway Herman
> I do only wheel-thrown
> or hand built work with commercial clay, and have no sodium silicate,
> Darvan, etc. in my studio. What could the source of the salt be that I am
> observing?
> Thank you!
> Dave Finkelnburg,
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