Cover an object with water-based clay. Cover clay in shellac, let dry. Remove object. Prepare a mold and place your clay into it, fill with plaster, and let harden.
Choose object to mold and place in a wooden frame, bury half of the object in sand. Mix plaster to the constancy of pancake batter and pour over object. Let the plaster dry completely, remove sand, coat plaster half with grease and pour second half of mold. Let second half dry completely and remove object from halves.
Ceramic molds are made up of two separate parts. Draw a line on the object where the part should be. Press the object into a square of water based clay. Boards are assembled around the clay to make a box with the clay in the middle. Press up against the sides of the boards so the plaster doesn't leak.
After securing the ceramic mold with straps, slowly fill the mold with slip. Allow 25 minutes for the slip to form a clay body on the inside of the mold.