Last summer, the International Cast Polymer Association (ICPA) held an informative multi-regional meeting at the headquarters of Ashland Performance Materials in Dublin, Ohio. The meeting featured several workshops, including one sponsored by Polytek Development Corp., an Easton, Pa.-based manufacturer of a variety of polyurethane mold rubbers and silicone liquid rubbers.
In the workshop, Jill Spohn, a technical sales representative for Polytek, showed attendees how to take an ordinary architectural objects such as crown molding, casement trim and baseboard trim and make an exact replica of an original piece using two-part silicone, existing shop supplies and a cheap frame made from an old laminate countertop. By doing so, she revealed a unique way to add style, distinction and diversity to a product line with a limited investment.
I recently met Spohn for a one-day workshop at Polytek’s factory in Easton. Before I arrived, I purchased a small corbel and trim piece at a local lumber yard. These would be my test pieces. I wanted to see what it would take to replicate these parts by making a mold, then casting a piece in engineered composites. Would it be simple? Cost-effective? Would my part turn out as detailed as the original?
Step 1: Create a frame or “box” to surround the original part with a one-inch gap around the sides of the original part. We used an old laminated countertop, cut it down and made a frame approximately one inch higher than our original part. Because polyesters don’t adhere to laminates well, they make a great surface for a mold box. Other options include glass, Teflon-coated baking pans or anything that will hold the silicone liquid until it cures.
Step 2: Mount the original part to the base of the laminate board using a ball of clay, hot glue or double-sided tape to hold the part firmly in place. The base edges of your original part (where it touches the base of the laminate mold) may need to be sealed with wax or clay to prevent liquid silicone from seeping under the part if it doesn’t lay flat on the frame base. Use clean clay or molding wax (available from various sources such as Gruber Systems, Composites One, Advanced Plastics and other suppliers) to seal the base of the part to the base of the laminate mold. This is the same clay and wax most manufacturers use to mount a floating bowl. Cheap clays may contain sulfur and are not recommended to use with silicones.