This is a very recent experiment, I have added 10% petalite to porcelain casting slip which has crushed shell additions. I recently made summer teabowls which had shell mixed in with the clay. The teabowls looked really interesting as the shell made the clay tear and pull apart. Unfortunately a few days after firing the bowls dissintergrated. After advice from Helen Moore I tried adding Petalite. This piece has been fired to 1260, I am going to try and re-fire with a pale green stoneware glaze on the inside. I will then experiment with throwing with petalite mixed in with the clay.