Emily P. Henderson on mon 13 jan 97
I've been pitfiring for about 6 years. I'm now making pots for my seventh
firing season. This is not easy and requires a lot of experimentation,
willingness to fail...I break a lot of pots, and patience. I fire at the
beach here in Oregon and have only one day to complete my firing. In the
summer months, because we are so far north, I can begin digging at daylight
(which is about 4:30 am), and can still easily see at 10 pm. I am not
allowed to "sleep on the beach" so to speak. The wood you use will make a
difference, the type, texture and water content of the sawdust, the sea weed
(if you use it) the animal fodder for the dung and even the weight of the
wood. The clay bodies are essential to my firing and, after experimenting
with between 120 and 150 different ones, I have 2 porcelains, one stoneware
and a red earthenware that: 1. Have enough structural integrity to allow
me to throw 2. Are smooth enough to accept a burnish 3. have the
ability to sustain significant thermal shock 4.(since I go for color), will
produce multiple colors when burnished and fired in wood because of the
chemicals resident in the clay bodies themselves. Black stuff (grey stuff)
is pretty easy to do, color, for me, anyway has been the challenge. I don't
use chemicals but some people do...I've even heard of some folks throwing in
their hotdogs for the nitrates they can contribute. This project isn't for
the faint hearted and takes A LOT of fuel. Vince can fill you in on the use
of slips and TerraSig....I need help here because I can't get it to stick to
my large pieces...I know its my coeffecient of expansion that is the problem
but... Vince, do you want add something that will help us all out here,
again? On this incredibly beautiful chill day here on the Coast. Emily
Vince Pitelka on wed 15 jan 97
> Vince can fill you in on the use
>of slips and TerraSig....I need help here because I can't get it to stick to
>my large pieces...I know its my coeffecient of expansion that is the problem
>but... Vince, do you want add something that will help us all out here,
>again? On this incredibly beautiful chill day here on the Coast. Emily
Emily -
You already know much of the following, but I will say it for the benefit of
anyone else who can use it. I have always applied my terra sig to a roughly
textured surface or to the dry-sanded surface of a good gritty claybody.
The smoother the surface, the less likely the terra sig will stick. Are you
applying it to the bone-dry surface? Are you burnishing the terra sig? Are
you burnishing under the terra sig? The latter is a sure-fire guarantee of
flaking terra sig. If you are burnishing, then you have no reason to use a
fine-grain claybody, like porcelain. You will get much better thermal shock
resistance from a coarser claybody, and you can sand the surface and then
put whatever terrasig over it for burnishing, and end up with just as smooth
a surface, but with virtually no chance of flaking. Of course the larger
the vessel, the more effect any shrinkage will have on the fit of the terra
sig. A properly prepared sig is so dense, that it cannot stand much
shrinkage of the claybody beneath unless it is really well-attached to the
surface.
My favorite claybody for bonfiring which can be made from standard ceramic
materials) is just equal parts fireclay, ball clay, goldart, and fine grog.
This is also a fine raku body, and also makes a great high-fire sculpture
body. The 25% grog will seem high to some, but it really is not excessive.
The clay even throws very well. The Pueblo potters use 50% or more
tempering materials in their clay, but of course their traditional pots are
entirely handbuilt.
- Vince
Vince Pitelka - vpitelka@Dekalb.Net
Phone - home 615/597-5376, work 615/597-6801
Appalachian Center for Crafts, Smithville TN 37166
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