Making a 2‑Part Mold of an Architectural Bracket


After Hurricane Katrina hit New Orleans, city native Chep Morrison used Mold Max® XLS II LOW SHRINKAGE silicone rubber to replicate an ornate bracket for an architectural restoration project near the Garden District.  

After the unique, two-part block-mold was made using a custom-shaped mold box, the ornate brackets were cast in a two-step process that involved coating the surface of the mold first using duoMatrix® NEO Polymer Modified Gypsum. This was done to create a hollow piece and reduce the overall weight of the casting.

Once the duoMatrix® NEO was applied and allowed to cure, the second step involved backfilling the hollow castings to add dimensional strength and stability to the bracket structure. Foam-iT!® 10 SLOW is a 10 lb. / cubic foot expanding urethane foam that was used to backfill the hollow castings. Foam-iT!® 10 SLOW expands approximately 6 times it's original volume and cures to a rigid finish. After measuring and mixing the foam, it began to expand and fill in all the nooks of the interior aspect of the hollow casting and was allowed to cure at room temperature (73°F / 23°C).

By using Mold Max® XLS II, Mr. Morrison could create many exact replicas of the original bracket, not only for this project but for future projects as well. In using duoMatrix® NEO and Foam-iT! 10 SLOW, the brackets display remarkable dimensional strength and stability, while maintaining an overall lightweight finish. Maintaining a lightweight finish enabled Mr. Morrison to easily install the ornate brackets, helping to reduce labor costs.

Materials Used in this Tutorial

Step 1: Preparing the Model