Expert: Sam Kelly - 9/15/2008

Question
I would like to make plaques to go on the wall, but each time i try it,it is a hit or miss on cracking when it drys in the middle of the back. I've been given different suggestions and have yet to figure it out. Is it drying too fast, moving it to quickly?

Answer
Hi d, Usually its because it is to thick and the outside dries quicker than the middle. If you are slip casting into a mould some clays just don't like to be a flat square.
You can add 10% molochite to a casting slip which will give it more 'tooth', molochite is the finest form of grog available and helps to keep all the clay particles together.
The best way to make tiles is to roll out clay on a slab roller, cut out the tiles and place them between 2 wooden boards(heavy enough to keep them flat) and forget about them for a week. This process compresses the clay and helps with warpage in the firing.

Sam