Chris Stanley on wed 3 oct 01
I am hoping someone out there can help shed some light on a topic raised by
one of my students while we were mixing a 55-gallon batch of deflocculated
casting slip this afternoon.
When was the first recorded use of deflocculated casting slips for the
production of ceramic ware?
My theory, which is probably wrong, but sounds good, is that since Terra
Sigillatas carry with them some form of sodium to suspend the light
particles, the invention of casting slips must have been in some way
connected to early burnished pottery coming from an area of the world with a
water source high in sodium. From time to time, I will demonstrate this
phenomenon to my classes by pouring Terra Sigillata into a bisque bowl and
allowing it to dry overnight and then removing the new cast bowl during the
next class. Hey, its worth at least two AHHS and a couple of "Way cools"
from the students!
My suspicions make me think that there are only several areas of the world
with water that has a concentration of sodium that would be high enough to
cause the deflocculation of clay. Utah, The Dead Sea, and Odessa, Texas are
on the top of my list! Our city water has a twang to it, and there is
brine water underground that is left over from a couple of million years ago
when we were a Sea. I doubt that Utah and Odessa are correct:)
The story I have told my students is that a young apprentice must have been
screwing off and instead of getting the fresh water from the stream for the
potters, they went to the sea shore to hunt shells for texture and just
grabbed a couple of pots of salt water thinking that no one would have known
the difference.
Thanks
Chris
iandol on thu 4 oct 01
Dear Chris Stanley,
Information to hand suggests Gypsum plaster was known in the Dynastic =
Egyptian era and was certainly used during the reign of Akh-en-aten for =
making casts. It is also probable that plaster moulds were used for =
making scarab beads out of a soda (Natron) fluxed clay. Your suggestion =
of North American sites is interesting so your students may wish to =
search for archaeological evidence of casting techniques among the =
aboriginal tribes, pre-European settlement.
Best regards,
Ivor Lewis. Redhill, South Australia
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