I haven’t been very good at keeping track of my clay tests recently. I need to blog about these as a way of keeping up with what tests I’ve run and what needs to be modified.
This red clay is one I’ve used alot at cone 6 without problems. Trying to use it at cone 9-10 has been a challenge. The first tests I ran were a success, so I mixed a big batch of it and some Mahavir feldspar. Subsequent tests showed this mix was very prone to warping at high fire temps. A mix of this clay with commercial clay does not warp, so I know it’s possible to use it in some capacity at high fire reduction. Since I’ve found similar problems with a low iron local clay, at this time, I believe it’s not due to the iron in the body but rather the lack of alumina at high temperatures. Tests with a high kaolin content seem to work well.
This body is an attempt to maximize the red clay usage while eliminating the warping. This mix needs way more flux. Was still 8% absorption at almost cone 9. I also think adding the extra sand was a mistake. It was still plastic, but I’m afraid it would increase the expansion of the body too much. I was thinking when I mixed this up that it would help fit the body to a glaze I was using, but I’ve since decided that lowering the expansion of the glaze is a much better idea. My new frit came in Friday so I’ll be testing that this week, I hope.
| Red clay non sandy deposity with sand and mahavir | 61.00 |
| White Sand Testing | 17.00 |
| Neph Sye A270 | 11.50 |
| EP Kaolin | 10.50 |
