Well, my last tests did not go well. One test bar (the sandy one with 16% absorption without anything added) was way over fired at 30% neph sye. It still had 11% absorption at cone 6 with 20% neph sye so I had not expected that result. I’m glad I had it on a cookie just in case.
The other mix was also over fired, but not quite as dramatically. I’ve added so much stuff to that batch for testing, I have no idea where it actually sits at. I took the cone 6 stuff. Its drying shrinkage was much too high. I added it half and half with some sandy clay that had high absorption. I had previously added 10% mahavir to this clay. Then I added 5.7% neph sye to a test bar. That amount was not enough. So then I added 9% to the whole batch. That amount was too much. So I’ve now added a couple of large cool bowls of the wet sandy clay. I did not add anything to them. Hopefully, this will bring the firing back up. We’ll see how that goes.
The next test tile was one that had nothing added. Its absorption was 3.5% which is only a hair to high for functional work. However, it’s drying shrinkage was 9.5% which is high. I think I may add some fine sand back to that one and then add some neph sye.
These were all fired on Wednesday. Anyway, here is my almost melted test bar.
