1. Safety considerations first, read the container labels and then read MATERIAL SAFETY DATA SHEETS.  KEEP OUT OF REACH OF CHILDREN. FOR INDUSTRIAL USE ONLY.
  2. Pre-measure resins. Our R1 FAST CAST® is 50/50 by volume
  3. If using with our fillers #M15, #HG3000 or #P1, pre-measure by volume, usually 50/50 or 60% resin to 40% filler for better detail.
  4. Mix (using the Jiffy Mixer® and electric drill) equal amounts of filler into resin side "A" and also in Side "B". Be careful of moisture contamination. Add Molecular Sieves to side "B" (refer to the label instructions for the amount).
  5. Read all the label instructions first. Spray auto primer on the RTV Silicone Rubber mold, let it dry for a couple of minutes.
  6. Mix each bucket of resin/filler again to get it back into solution.
  7. Pour both resin/filler solutions into a third mixing bucket and mix completely for 30-45 seconds. For the #709 resin, mix for 1 3/4 -2  minutes. Avoid whipping in air. Keep the mixing blade below the vortex. Pour the mixture into the rubber mold. Mixing time may have to be shorter at 80o F.
  8. Dust the back of the casting with a hair dryer to break any bubbles just before the resin gels. Demold when firm in 10 to 30 minutes. Let the casting cure flat overnight. Choosing the right resin and filler combination for your casting: Here is a quick guideline. A retail item should have the no odor #891 or Roto-One. Fillers are optional. Medium to large parts usually benefit by using #M15 and or #HG3000 to give it less weight or more weight and improved dimensional stability, less shrinkage, stronger physicals. We can recommend when you order. The #709 is for mass castings and does need to be mixed with fillers to prevent cracking. If using 50/50 by volume, you can pour unlimited thickness in one pour or pour layer after layer (each layer has to come to a firm gel for about 10 minutes before the next layer is poured). For making Machineable Plastic and patch repairs, refer to it's own brochure and instructions. A quality casting will be smooth and dry on the back surface.


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 MSDS

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.

  1. Wax or use SP Mold Release on the inside of the plywood. Apply the appropriate mold release on the pattern.
  2. Mix 10 parts of white Base with 1 part of blue Catalyst (shake first, it settles) completely until you have an even light blue color with no streaks. Do not whip in air during mixing. Keep the Jiffy® Mixing Blade below the vortex. Use the Large Spatula on the sides and bottom of  the mixing container and mix that amount into the rest of the rubber. If you have a vacuum chamber, de-air the rubber. Pour a thin stream of the mixed rubber from about 18" above the highest point of the pattern to break any air bubbles during the pour. Let the flow lead, just continue pouring on the high point. Fill to about 3/4" over the highest point.
  3. Let the rubber mold cure for 24 hours at 75o F. or higher with medium relative humidity. If you are in a dry desert area, have an open pan of water next to the rubber. The rubber cures by heat and humidity after being catalyzed.
  4. After 24 hours, if the rubber feels firm, remove the rubber mold from the pattern and let the rubber mold post cure for another two days before using. The extra post cure time will give you a longer mold life.
  5. The first casting out of the mold will probably have some of the mold release residue on it.
  6. For production castings, we recommend using an auto primer.
  7. SMS(Silicone Mold Saver) is applied when you need maximum amount of castings out of the mold, or to extend the life of an old mold that is about ready for the graveyard. SMS must be fog sprayed only (not brushed), at the end of the day and let cure overnight. Instructions are on the container.
  8. The used rubber mold can be recycled if cut into small bits and pushed into fresh rubber after poured over a 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.

How To....​


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.

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