Numo Jaeger and Michael Miller on thu 17 jul 97
Hi all! This might be a good question for VINCE!
Does anyone know about black core pottery from Mexico? A student of mine
brought in a piece that had a tanish cream colored exterior and a black core
center.
It was a small sculptural piece which looked as if it were pit fired in one
fashion or another.
Perhaps a black core from carbon being trapped inside? Or did it have a
black core of clay in it. The person said she got it close to Oxaca.
How coul one get a black core and end up with a surface that looks oxidized.
-Numo
Numo
Vince Pitelka on fri 18 jul 97
At 06:55 PM 7/17/97 -0400, you wrote:
>----------------------------Original message----------------------------
>Hi all! This might be a good question for VINCE!
>
>Does anyone know about black core pottery from Mexico? A student of mine
>brought in a piece that had a tanish cream colored exterior and a black core
>center.
Numo -
Thanks for your confidence, but I do not have any idea. I would like to
know. I have several pieces of Oaxaca blackware, but this one is new on me.
Someone out there must know what it is.
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
1560 Craft Center Drive, Smithville TN 37166
Lynda Jones on fri 18 jul 97
You can get a black core inside with an outside that looks like
oxidation by spraying or brushing on slip-resist over bisque-fired pot.
After pit firing clean off the slip.
Recipe:
China clay 3 parts (vol)
Flint 2 parts (vol)
John Guerin on sat 19 jul 97
In a message dated 97-07-18 09:30:10 EDT, you write:
<< Does anyone know about black core pottery from Mexico? A student of mine
brought in a piece that had a tanish cream colored exterior and a black core
center.
It was a small sculptural piece which looked as if it were pit fired in one
fashion or another.
Perhaps a black core from carbon being trapped inside? Or did it have a
black core of clay in it. The person said she got it close to Oxaca.
How coul one get a black core and end up with a surface that looks oxidized.
>>
You are right in your assumption that the black core comes from the carbon
being trapped inside. In an outdoor firing, the pottery is not fired hot
enough to vitrify all the way through. Especially with a lot of the mexican
pottery where they don't waste a lot of fuel. It is usually just fired hot
enough to get it over the border. Even some of the prehistoric pot sherds
left by southwestern indians that came from pottery a thousand years old
display the same "black Core". You can prove this by refiring a piece of this
pottery in a modern kiln. Just make sure you don't fire it over 2,000 degrees
F, because it is a 'low fire' clay. It was probably originally only fired to
about 1,000 degrees F, so you can refire it to 1,600 - 1,800 and the carbon
will burn out. That temperature may even cause a slight change in color.
My wife uses the large mexican flower pots on the back patio. They only last
about two or three years before they start to crumble because the water seeps
through the sides. This is also caused by underfiring. The last one we
bought, I refired to 1,800 degrees F in my large kiln and the orange color
changed to red. Also, there is no sign of deteriation after three years.
John Guerin
Tucson, AZ
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