SLIP CAST MOLD MAKING, SIMPLIFIED

A mold can be made from virtually any object. Your original piece (or model) can be made of clay, wood or plaster. The more intricate the design of the object the more complicated the mold making process.

Let me show you an overly simplified demonstration of the mold making process for the mold of a ball made of wood.

1. Roll out a piece of modeling clay that is water based.

2. Press the ball into the clay so that it is half in the clay and half out.

3. When the clay is dried to the consistency of leather (leatherhard) the edges are trimmed up to be square.

4 . Because the clay and wood are porous, a sealant is applied. Two coats of Orange Shellac over the ball and surface of the clay can be brushed on with a soft brush. Let dry for 15-20 minutes, dust lightly with talcum or baby powder.

5. The whole surface is covered with a Parting Agent of Tincture of Green Soap, using a soft brush. With a dry brush, pick up all excess of the parting agent. The surface of the ball and clay should be slick.

6. Casting boards that have been wiped with Parting Agent are placed around the four sides of the clay and are clamped together using clamps. Seal where the clay meets the boards.

7. Slip Cast Molds are made of plaster (USG #1 Pottery). A plaster and water mixture is then poured into the boxed clay and ball, and left to dry for about 20 minutes (depending on size of object).

8. After the casting boards are removed, the plaster /clay mold is then turned over and the clay is lifted from the box, leaving the plaster half of the mold in the box.

9. Keys are carved into the plaster portion (simple round holes). These are what help fit the final two pieces of plaster together.

10. The plaster half of the mold is brushed with a light layer of Powder or Talc as in step 4. The second half of the mold is now cast by repeating steps 5, 6 & 7.

11. After the plaster dries, the plaster boards are removed and both sides scraped clean.

12. Using a wedge and gently pulling, the two pieces of plaster are separated at the parting line.

13. The original model is released from the mold by genteel prying or air pressure.

14. The mold is left to dry for ~5 days after a pour hole is carved. The placement of the pour hole depends on the object design.
*(When actually using the mold in production, this hole is where the slip is poured into. The slip is allowed to dry for a designated period of time, then the excess slip is poured out of the hole.)

15. The finished ball, once poured using the mold, will have a hole and seams where the two halves of the mold came together that will be sanded away. (What would you do with a ball with a hole it? How about adding a top an making an Ornament!