How To Make a Metal Cold Casting Using Matrix Dryve™ Polymer Gypsum


Reproducing the look of metal (bronze, brass, copper, etc.) is a common application for Dryve™ because you can achieve the look of real metal at a fraction of the cost. –325 mesh metal powder is recommended and should be pre-mixed with Dryve™ powder prior to adding water. An accurate gram scale is necessary. Adding a dark pigment (Buddy Rhodes™ Carbon Black for example) to the dry mix will give the final casting added definition and dimension.

The chart below outlines example mix ratios for use with real metal powders.  Measured by weight; gram scale required:

Metal Powder Dryve™ Powder Water Metal Ratio Pigment
Aluminum 100 Parts 50-60 Parts 100 Parts 2 Parts
Brass 100 Parts 40-50 Parts 200 Parts 2 Parts
Bronze 100 Parts 30-40 Parts 200 Parts 2 Parts
Copper 100 Parts 50-60 Parts 200 Parts 2 Parts
Nickel-Silver 100 Parts 40-50 Parts 200 Parts 2 Parts


Metal powders are available from Smooth-On or your Smooth-On distributor. WARNING: Adding metal powder will reduce the pot life significantly. Matrix™ Retarder will extend the working time of the material if necessary. See Matrix™ Dryve™ Technical Bulletin for details.

Mix a small initial batch using metal powder as shown in chart above and brush mixture over mold surface. Let cure for 10-15 minutes. Mix a 2nd batch using no metal powder – 100 parts Dryve™ to 27 parts water by weight. If using a hand layup technique, dip fiberglass matting into liquid. Squeeze out excess and lay over previous layer. Repeat until 3/8” (1 cm.) thickness is attained.

Post Finishing Cold Cast Bronze Elements - To bring forth the metallic finish, buff with steel wool or sand paper (400 grit). Patina coloring can then be done using cupric nitrate (green) or ferric nitrate (yellow)

IMPORTANT: Casting must be sealed with wax or clear acrylic spray to prevent oxidation.