No Vacuuming – No Scale – Easy To Use . . . OOMOO® 25 is an easy to use silicone rubber compound that features a convenient one-to-one by volume mix ratio (no scale necessary). It has a low viscosity for easy mixing and pouring . . . vacuum degassing is not necessary. This product cures at room temperature with negligible shrinkage. OOMOO® 25 has a 15-minute pot life and 75 minute cure time.
For The Novice Mold Maker - OOMOO® silicones do not have great tear strength. They are good for making simple one or two-piece block molds. If you require a high-tear strength silicone, Mold Max® silicones are recommended.
OOMOO® 25 is suitable for a variety of art-related and industrial applications including making one and two-piece block molds for sculpture and prototype reproduction, casting plaster, resins and wax. OOMOO® silicones are also suitable for electrical potting and encapsulation applications.
Safety – Use in a properly ventilated area (“room size” ventilation). Wear safety glasses, long sleeves and rubber gloves to minimize contamination risk. Wear vinyl gloves only. Latex gloves will inhibit the cure of the rubber.
Store and use material at room temperature (73°F/23°C). Storing material at warmer temperatures will also reduce the usable shelf life of unused material. These products have a limited shelf life and should be used as soon as possible. Premix Parts A and B thoroughly before using.
Cure Inhibition - Silicone rubber may be inhibited by certain contaminants in or on the pattern to be molded, resulting in tackiness at the pattern interface or a total lack of cure throughout the mold. If compatibility between the rubber and the surface is a concern, a small-scale test is recommended. Apply a small amount of rubber onto a non-critical area of the pattern. Inhibition has occurred if the rubber is gummy or uncured after the recommended cure time has passed. Materials found to cause cure inhibition include sulfurbased modeling clays and latex rubber.
To prevent inhibition apply a sealing agent . . . apply a “barrier coat” of clear acrylic lacquer sprayed onto the clay surface.
Applying A Release Agent - Although not usually necessary, a release agent will make demolding easier when pouring into or over most surfaces. Ease Release® 200 is a proven release agent for making molds with silicone rubber and for releasing new silicone from cured silicone. Mann Ease Release® products are available from Smooth-On or your Smooth-On distributor.
Because no two applications are quite the same, a small test application to determine suitability for your project is recommended if performance of this material is in question.
Measuring & Mixing - Before you begin, pre-mix Parts A and B thoroughly. After dispensing equal amounts of Parts A and B into mixing container, mix thoroughly for 3 minutes making sure that you scrape the sides and bottom of the mixing container several times. Mixture should have a uniform color with no color streaks. If you observe color streaks, continue mixing until they are eliminated.
Pouring – For best results, pour your mixture in a single spot at the lowest point of the containment field. Let the rubber seek its level up and over the model. A uniform flow will help minimize entrapped air. The liquid rubber should level off at least 1/2” (1.3 cm) over the highest point of the model surface.
Curing – Allow to cure for 75 minutes at room temperature (73°F/23°C) before demolding. Post curing the mold an additional 4 hours at 150°F (65°C) will eliminate any residual moisture and alcohol which is a by product of the condensation process and may inhibit some resins. Allow mold to cool to room temperature before using. Do not cure rubber where temperature is less than 65°F/18°C.
Using The Mold – No release agent is necessary when casting wax or gypsum. Applying a release agent (Ease Release® 200) prior to casting polyurethane, polyester and epoxy resins is recommended to prevent sticking and mold degradation.
Mold Performance & Storage – The physical life of the mold depends on how you use it (materials cast, frequency, etc.). Casting abrasive materials such as concrete will quickly erode mold detail, while casting non-abrasive materials (wax) will not affect mold detail. Before storing, the mold should be cleaned with a soap solution and wiped fully dry. Two part (or more) molds should be assembled. Molds should be stored on a level surface in a cool, dry environment.
Mold box construction, model preparation and release agent application for a 2 part pour on mold are covered in this video.
This mold making tutorial video shows how to make a one piece silicone block mold using OOMOO® silicone rubber
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Not premixing silicone can result in the material not setting up correctly...
This mold making essential video demonstrates the double mix and pour technique using a 1A:1B OOMOO silicone rubber.