Cover work as it dries if your work is;
- thin,
- has joins (i.e. handles),
- uneven in dampness (i.e. one part is much dryer),
- flat (i.e. a tile), or
- drying in a hot or drafty environment.
Slow and even drying gives clay the best chance of getting through the drying process without cracking or warping. The type of clay used can also affect cracking and warping. In general clays with more grit or grog are less likely to warp and crack.