Making A Brush-On Mold With A Lightweight Support (Backer)

Making A Brush-On Mold With A Lightweight Support (Backer)

The advantage of making a mold by brushing rubber onto the model is that it minimizes the amount of rubber used, saving you material costs. Making a brush-on mold, however, requires more time and labor vs. pouring rubber. The following is a demonstration on how to make a mold of stone veneer using Rebound® 25 Platinum Mold Rubber and Foam-It® 5 Rigid Foam as a rigid lightweight foam backer. Rebound® 25 is an incredibly strong flexible rubber. Mixed 1A:1B by volume (no scale necessary), Rebound® 25 self thickens and will hold a vertical or inverted surface and will cure to a soft Shore 25A rubber. Foam-It® 5 Rigid Foam consists of two-component system that is versatile and easy to use. Foam-It® 5 will expand many times the original volume and develop a uniform cell structure.

1 - Secure original models to acrylic coated baseboard with hot melt glue gun to prevent movement during the mold making process.	2 - Place models in center of baseboard. Keep a 1'' (2.5cm) space between stones.	3 - Spray all surfaces with Ease Release® 200 Mold Release.
4 - Dispense equal amounts of Rebound 25® A + B into mixing container.	5 - Miix rubber thoroughly, make sure you scrape the sides and bottom of container many times. Eliminate all color streaks.	6 - Brush a very thin layer onto model. Work rubber into fine detail.
7 - Cover the entire model and create a 3'' (7.6 cm) flange in all directions around model. Allow rubber to cure 60 minutes until tacky.	8 - 2nd Layer - Mix and apply another layer of rubber this time add a small amount of SILC-PIG® color pigment. This will help you distinguish one layer from the next.	9 - Rubber should be sticky to the touch, does not come off onto your glove. If rubber is still wet, do not apply the next layer.
10 - After model and board are covered, let rubber cure for 60 minutes until tacky.	11 - Measure and mix a small amount of Rebound® 25 A+B. Add 4 drops of Thi-Vex thickener to every 1 oz. of mixed Rebound® 25.	12 - Use thickened rubber to build up sections for support.
13 - The top of the mold is reinforced.	14 - 3rd Layer - Mix and apply another small batch of rubber.	15 - After model and board are covered, let rubber cure 60 minutes until tacky.
16 - 4th Layer - Mix and apply a final layer of rubber.	17 - Let all layers cure at least 6 hours at room temperature ( 72˚F/22˚C).	18 - Construct mold box and secure with drywall screws.
19 - Use a razor knife to trim the rubber. Sharp clean edges will help the rubber mold register with the support shell.	20 - Center mold box over mold.	21 - Seal all seams with hot melt glue.
22 - Apply a liberal coat of Sonite Wax® to the entire surface of the mold, baseboard and mold box.	23 - Use a piece of melamine board to completely cover the mold opening. This will minimize voids in the foam with back pressure. Using a ¾” (2 cm) drill bit, drill 2 holes in the board spaced a few inches / cm apart. Next, apply a liberal coat of Sonite Wax	24 - Measure and mix equal amounts Foam-iT! 5.Foams expand to full volume in 5 minutes, develop handling strength in 30 minutes and fully cure in two hours.
25 - Pour FOAM-iT® 5 into mold cavity.	26 - Remember, these products cure quickly. Do not delay between mixing and pouring.	27 - Make sure that, when the board is placed over the mold opening, the holes are over the mold cavity and rising foam will be able to make it through.
28 - Hold board firmly in place. As foam rises in the mold cavity, some foam will grow out of the drilled holes. After the foam stops growing, you can let go of the board.	29 - After 20 minutes, cut excess material that came through holes. Gently remove board.	30 - Turn box over and remove baseboard. Remove mold and models from support backer.
31 - Some of the benefits of making Brush-On molds include lower cost in materials, lightweight, and good flexibilty.	32 - Mold is ready for production casting of stone veneer.	33 - You too can create a focal point in your living room with concrete stone veneer.