Architectural Restoration: Making a Rubber Mold of a Plaster Column

This video tutorial features the making of a brush-on rubber site mold. Some of the columns in this commercial building are damaged -- a brush-on rubber mold with plaster mold shell is made of an intact column in order to cast plaster replacements for the damaged columns.

Mold Materials: Poly PT Flex 20 (a soft, polyurethane rubber) and a Plaster/Burlap Two-Part Mold Shell. A full list of materials used are listed at the end of the video.

The Steps: 

Part I: Prepare Column & Make Brush-On Rubber Mold 

Step 1: Establish Mold Area 

Step 2: Apply Sealer [Pol-Ease® 2350 Release Agent] & Let Dry 

Step 3: Make Flange Supports for the Top & Bottom of the Mold Area 

Step 4: Apply Release Agent [Pol-Ease® 2300 Release Agent] 

Step 5: Mix Rubber 

Step 6: Brush On Rubber Allow Rubber to Fully Cure

Part II: construct Two-Part Plaster Mold Shell 

Step 7: Spray & Brush Out Release Agent [Pol-Ease® 2300 Release Agent] 

Step 8: Mix Plaster & Construct Two-Part Mold Shell Allow Plaster to Fully Cure Part III: Remove Mold Shell & Rubber Mold 

Step 9: Carefully Remove Mold Shell 

Step 10: Carefully Remove Mold Part IV: Cast Plaster in Mold 

Step 11: Pour Plaster into Mold