The first step in making a silicone rubber mold is the weighing of the base material. Measure sufficient base material for your application requirements. Use a clean container that is approximately four times the volume of the base material being weighed. This extra container capacity is required to allow adequate room for mixing and deaeration.

When using less than a full kit, the curing agent must first be weighed and measured to provide the proper 10:1 weight ratio.
After the curing agent has been added to the base material, mix thoroughly using a clean, flat-bladed spatula or paint stirrer until all visual streaks disappear. Material clinging to sides and bottom of the container should be folded into the main contents twice during the mixing cycle. Using a power mixer, only two 20-second cycles are required for thorough mixing. The sides and bottom of the container should be scraped with a spatula between cycles.

Air entrapped during the mixing cycle must be removed to eliminate voids in the silicone rubber mold-making material before cure. As the vacuum is applied, the mixture will rapidly "froth" (expanding to approximately 4 times its original volume), crest, and eventually recede to approximately its original level. Using a vacuum of 29 inches mercury, deaerating is complete approximately two minutes after the "frothing" action ceases. If the container size is found to be inadequate for its contents, the vacuum can be "broken" during operation to reduce bubble formation. If molds are to be used for only a few duplicates, and care is taken in pouring, deaerating is not absolutely necessary.

Pour the silicone rubber contents from approximately 8 centimeters (3 inches) above the pattern surface. On complex masters, the material should be poured in a continuous stream over the entire surface, and the thin coating allowed to settle for approximately 5 minutes. Any bubbles must be broken with positive air pressure or by passing a spatula gently across the surface. Remaining contents may then be poured into the mold frame. Release agents are not required on most surfaces. However, on extremely porous material such as wood, a lacquer coating dried and coated with Vaseline will greatly enhance the releasing . Vaseline on other substrates will create a high gloss finish on the resulting mold.

RTV 770 silicone molding material cures, regardless of thickness, to a durable, resilient rubber at room temperature 24 hours. Cure may be accelerated with heat for faster processing.

To demold the cured silicone rubber from the master, fist remove all frame support materials. Gently loosen the edges of the mold and use a slow, continuous pulling motion to strip the mold from the master surface. To prevent the mold from tearing, avoid using short sudden jerks or sharp instruments when removing the mold form the master.

NOTE: Mandatory and recommended industrial hygiene and safety procedures should always be used when handling materials.