HOW TO MAKE A FLEXIBLE RTV SILICONE RUBBER MOLD
This is how to estimate the amount of RTV Silicone Rubber needed. Measure the mold cavity (length x width x height in inches) to get the total cubic inches. Subtract the size of the pattern. Example: The plywood case is 1.75" thick x 12" long x 14" wide = 294 cubic inches. The pattern is 1" thick x 10" long x 12" side = 124 cubic inches. The difference is = 174 cubic inches. The rubber weighs about .038 lbs. per cubic inch, so take the 174 x .038 = 6.6 lbs. of catalyzed rubber. Read the instructions on the containers and the M.S.D.S.
Example for making a flat casting such as a wall plaque:
Mount the pattern on a plywood base. Do this on a flat table. Use silicone adhesive, dispensed from a tube, around the perimeter to prevent any RTV from going in between the pattern and plywood. Wipe off any excess adhesive. Now screw the plywood sides to the plywood base to enclose the pattern.
R1 FAST CAST® is a two part liquid urethane casting resin that sets up to become a rigid or flexible plastic with a few minutes after being mixed. Take time to read this plastic 'How to...' information, and the container labels for good results with the parts you make. This is a guideline only, hands on experience is the best teacher. We supply all of the casting materials needed to make molds and castings.
TOOLS AND EQUIPMENT RECOMMENDED FOR CASTING AND MOLD MAKING
The usual variety of wood working hand tools plus putty knife, razor blade knife, level, Rubber Spatula, "U" Channel Knife, Jiffy Mixer®, rasp, hand saw or electric power saws, hair dryer, sander, 1" and 2" wide inexpensive paint brushes, postal scale in ounces and another up to 25 lbs.. Milwaukee® electric hand drill (#124-1 Magnum Holeshooter, var. speed, reversible). Wagner™ airless spray gun #200 series with extra quart containers and lids. Fire extinguisher and fire storage cabinet. Metal trash can with lid. A level, Formica topped table. Plastic mixing buckets in the 1 to 3 gal. sizes (tall and narrow without inner ribs or cavities molded in). Do not use styrene based plastics as some disintegrate upon contact with resins. If you purchase 55 gal. drum quantities, then you will need a drum dolly. Other useful items are duct tape, box of 1 1/4" sheet rock screws, 3/4" particleboard or plywood, variety of sandpaper, Plasti-Clay® modeling clay, and silicone adhesive in tubes. The above items are for a shop that wants to get into production. If you are just experimenting or making prototypes, you can eliminate much of the above.