I did a Cone 10 fire with the four different types of paper clay mentioned in my earlier post.
From left, is Gault 10 paper clay, Southern Ice Porcelain paper clay, a red-bodied paper clay, and Black Mountain sculpture paper clay.
These test tiles went through the bisque fire first and then to Cone 10 reduction. Below are the results.
From fresh clay to bone dry greenware:
All showed approximately 4 - 5% shrinkage.
After Cone 10 fire (total shrinkage, from fresh clay to Cone 10 fired):
Gault 10 Pclay - 11.9%
Southern Ice Porcelain (with feldspar) paper clay - 9.4%
Red-body paper clay - 13%
Black Mountain sculpture paper clay - 10.4%
Caveat: The same caveat applies to this test.
Visible change in Cone 10 fire compared to Cone 5.
1. The Gault 10 Pclay turned a deeper buff color.
2. The feldspar crystals in the Southern Ice Porcelain paper clay "popped more. Some specks of iron showed up, and I don't know where they came from. Perhaps, a contaminant.
3. The red-bodied paper clay turned a very warm orange-brown color.
4. The Black Mountain sculpture paper clay turned a very deep brown-black.
At Cone 10, these test tiles were completely vitrified and you can tell the difference in the sound when these tiles were struck together compared to the Cone 5 fired tiles.
On the Gault 1o Pclay test tiles, I decided to also test out some colored slips - blue, green and black.