Rachel and Eric on tue 9 nov 99
Wise potters,
The potters of San Bartolo Coyotepec in Oaxaca fire blackware in
sunken kilns. To do this they fire the kiln until the pottery is a low red,
perhaps between 1200 and 1300F. Then the kiln is stocked to the max and
sealed over, top and stock hole, with mud- completely sealing it. Next day
the pottery comes out black and sooty. When washed it is black and shiny.
If you break it, the shard will show black along the edges and grey in the
heart.
Is the black achieved by reduction or carbon impregnation?
In their 1978 book, "A Potter's Mexico", Irwin and Emily Whitaker describe
the Coyotepec firing as follows
"Despite a carefully nurtured Coyotepec myth, there is nothing unusual or
mysterious about the technique producing blackware. It results from a firing
process best described as "smudging". Toward the end of the firing, the
potter adds fuel which will produce a great amount of smoke, and he then
seals the kiln completely, usually by shoveling damp earth over the top and
the stokehole. The result is a black, carbon-saturated ware. (Technically
speaking, this black color is not the result of "reduction"; that is, the
introduction of carbon monoxide into the kiln to reduce the oxigen ratio of
the minerals in the clay, thus changing the red iron oxide to black iron
oxide. While this may happen to a degree, the black color is primarily free
carbon impregnating the ware. Reduction per se does no leave carbon present.)
I have been describing this the Coyotepec firing as redution to
innocent ears. If I've been blowing smoke in those ears all this time I'd
like to know it. And there is no one I trust more on the matter than the
2,000 or so of you mudbrains.
cordially yours, Eric
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Rachel Werling, biologist
and/or
Eric Mindling, potterologist
Manos de Oaxaca
AP 1452
Oaxaca, Oax.
CP 68000
M E X I C O
http://www.foothill.net/~mindling
phone 011 52 (954) 7-4534
fax 011 52 (952) 1-4186
email: rayeric@antequera.com
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