Nathan (bigbearok) wrote,

Pennsic Clay Update

So one of my projects for this next year was to work with some "wild" clay that I dug in Pennsylvania.

Here are the problems with it: It's full of sand and debris, it's not very elastic, and I have no idea what temperature it will fire to.

1: Sand and debris: In order to improve the clay I need to clean it by removing as much sand, pebbles, tree roots, and other debris as I can. To do this I added water to the clay and made a thin slurry which I then passed through two sieves. The first was a regular cooking sieve, they kind made from wire mesh sold at any department store or grocery store. This removed the large pebbles, roots, and some of the larger particles of sand. The second sieve was a #80, which is quite fine. I passed the slurry through this and it removed even more sand and other particles. After this part I poured the slurry onto a large plaster bat to dry it out.

2. Not very elastic: One of the valuable aspects of clay is it's elasicity. Clay needs to be workable in order to be useful, otherwise it's just mud. This clay, both before and after cleaning cracks easily. This by itself doesn't make it unsuable, but to be formed into useful objects by handbuilding (pinch pots, coil, slab, wheel) it needs to be much more pliable without cracking. One solution to this may be to make pass it though yet another finer sieve to try and get some of the smaller particles out. I may also try to make it into a slip and do casting on plaster. Adding some ball clay may also improve the elasticity.

3. Firing Temperature: To find out what temperature the clay will fire to will require testing. I know that the raw clay will make it though the bisque (~1900F), but I need to test the cleaned clay. At the studio we fire to Cone 10, which is about 2300F, which is pretty much the upper level for ceramics. I have some test beads in the kiln now to see if they will survives that temperature. Most likely they will melt and slag instead of maturing and hardening. If it survies, great. If not, I can work at the lower temperatures with it, but it's more difficult since I have to rely on a low-temp firing rather than the weekly high-fire that we do at the studio.

More updates and perhaps some pictures at some point.
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