A pattern release agent should then be wiped or sprayed on the pattern. Spreading a light coat of release agent on the sides and underside of the top of the frame will facilitate release.
A good pattern release agent can be made by combining 5 percent petroleum jelly and 95 percent solvent. Combine the materials and let stand overnight – then shake by hand to provide a good mix.
SILASTIC RTV-4136-M Curing Agent contains a pigment which acts as an indicator for proper measuring and mixing. Thoroughly shake/stir the curing agent before use so that any sedimented pigment is redispersed.
Weigh 10 parts of SILASTIC RTV-4136-M Base and 1 part of SILASTIC RTV-4136-M Curing Agent in a clean container, then mix together until the curing agent is completely dispersed in the base. Hand or mechanical mixing can be used, but do not mix for an extended period of time or allow the temperature to exceed 35°C (95°F). Mix sufficiently small quantities to ensure thorough mixing of the base and curing agent. It is strongly recommended that entrapped air be removed in a vacuum chamber, allowing the mix to completely expand and then collapse. After a further 12 minutes under vacuum, the mix should be inspected and if free of air bubbles, can then be used. A volume increase of 23 times will occur on vacuum de-airing the mixture, so a suitably large container should be chosen.
Note: If no vacuum de-airing equipment is available, air entrapment can be minimized by mixing a small quantity of base and curing agent, then using a brush, painting the original with a 12mm layer. Leave at room temperature until the surface is bubble-free and the layer has begun to cure. Mix a further quantity of base and curing agent and proceed as follows to produce a final mold.
Addition of Curing Agent
Automatic mixing equipment handles SILASTIC RTV-4136-M Liquid Silicone Rubber efficiently. The product is de-aired before shipment when packaged in drums.
SILASTIC RTV-4136-M Liquid Silicone Rubber Curing Agent should be mixed into the base material just before use (with either manual or mechanical stirring) in the amounts of 10 parts base to one part curing agent by weight. For the best curing results, use metal cans, clean glassware or unwaxed paper containers for mixing the base and curing agent. Inclusion of air during mixing may cause avoids in the finished mold. Entrapped air may be removed by applying a vacuum of 28 to 29 inches of mercury. Under such a vacuum, the material will expand to three to four times its original volume. As the froth collapses, the mixture will recede to its original volume. The vacuum should be held one or two minutes longer before releasing.