Iâ€™ve been taking pottery classes for a year. I made some flat wall pieces for a special raku firing. They are flat slab built, about 4 Â½ by 6 inches. I carved them extensively, in Frank Lloyd Wright style stained glass designs. I put about 4 hours work into each one.
They all got through the bisque firing just fine. But 3 of the 4 cracked during the raku firing. Not along the incised lines I made, Iâ€™m pretty sure it was because our instructor set them upon blocks to be able to pick them up from the kiln during firing, and they must have absorbed the heat unevenly.
Anywayâ€¦I want to make them over again, and fire them conventionally. But I donâ€™t want to put in all that carving labor.
Studio staff suggested I glue the pieces back together, then make a plaster mold, and push new very moist slabs into the resulting mold. I bought casting plaster already that states on the box it is good for fine detail.
But studio staff were sketchy about how to make the plaster mold exactly. No one had ever actually done it. Especially considering the pieces I am molding are flat. How would I get the originals out again? Apply a film of something, like Vaseline?
Can you offer me any instructions?