DO NOT use grease, WD-40, vaseline or any other oil-based substance like suggested above, as your mold release. The whole point of using plaster is to take advantage of the capillary/wicking action of the material, to pull water from the clay and set it up faster - if you go and use something oil-based as a mold release, you've now clogged the pores and severely diminished capillary action, if any at all.
Use actual "mold soap" or purelube/greensoap, which are the products that should be available from any ceramics supply. Alternative is diluted Murphy's Oil Soap.
- Min likes this