Handout #3: Silicone Tube Molds

ART 35  ~  SCULPTURE: CASTING

Sean M. Monaghan, M.F.A., Instructor

To make flexible rubber molds quickly and inexpensively, silicone sealer in 10 oz. rigid caulking tubes can be used. You'll need:

1. “GE Silicone I, 100% Clear Silicone Rubber Sealant, for Windows and Doors.”
2. A bucket or bowl with about two quarts of slightly warm water.
3. 'Dawn' concentrated dishwashing detergent.
4. Cheesecloth, cut into strips (for larger molds).
5. Plaster and jute for making a mother-mold.
   1. Prepare your pattern as always: seal any cracks, attach to a board if necessary, coat with mold release, establish any parting lines, etc.
   2. Put 1 – 2 tablespoons of Dawn detergent into the bucket of slightly warm water.
   3. Spread some Dawn onto your hands as a release agent. Repeat during process.
   4. Squirt three or more full squeezes of Silicone I caulk into the water.
   5. Gather the strands of silicone and form it into a 'patty' in your palm.
   6. Place over your prepared pattern, being careful to eliminate air bubbles and pushing away water droplets.
   7. Repeat above steps as necessary, until you have at least 1/4" thickness for small pieces, up to 1/2" for larger pieces. Several layers of cheesecloth may be added-after applying 1/4" layer of silicone-on larger pieces by pressing pre-cut strips over silicone, and continuing with more layers of silicone patties, encasing cheesecloth.
   8. When silicone has cured, make a plaster and jute mother mold.

Notes: Silicone rubber emits acetic acid when expose to air. Use adequate ventilation. Always check the expiration date—old silicone may not cure properly. Silicone will get firm in 30 minutes or less, and may take up to 24 hours to fully cure. Humidity slows the cure of silicone. Clean up tools and hands with mineral spirits or turpentine. Do not use silicone for items that will be poured at 400Fº or more.