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How do I successfully make a crystal clear casting?
Preparation Selecting A Mold Rubber Pre-Heat The Mold Measuring
Ventilation . . . good ventilation is essential. You must wear a NIOSH approved respirator to minimize inhalation of residual fumes. Wearing disposable gloves and long sleeve garments will help minimize skin contact. (Refer to safety information on reverse side of this technical bulletin & MSDS). Make sure mixing tools & containers are dry. Product has a limited shelf life. Use as soon as possible.
Selecting A Mold Rubber . . . Crystal Clear Plastics should be cast into Smooth-On Mold Max™ Silicones or Smooth-On urethane mold rubbers. Do not use other silicone or urethane rubber products. If you are unsure about surface compatibility, a trial casting should be made. To prevent cure inhibition, post-cure newly made Mold Max™ silicones for 8 hours at
150° F / 60° C and let cool prior to casting resin. Polyurethane rubber molds should be dry and require a coat of a suitable release agent (Universal Mold Release available from Smooth-On) before casting.
For Best Results . . . Pre-heat the rubber mold at 212°F / 100°C for 4 hours before mixing & pouring Crystal Clear.
This will minimize the chances that cured castings will exhibit casting phenomenon such as fish-eyeing, suck back,
corner rounding, large bubbles, etc.
Measuring . . . Crystal Clear plastics should be stored and used in a warm environment (72° F / 22° C).These products have a limited shelf life and should be used as soon as possible. The proper mixing ratio is 100A:90B by weight. You must use an accurate scale (gram scale) to weigh these components properly Dispense the required amount of Part A into a mixing container. Weigh out the appropriate amount of Part B and combine with Part A. Important: Shelf life of product is drastically reduced after opening. Immediately replace container lids after dispensing. Use remaining product as soon as possible.
Casting Thickness Curing Post Curing
Post Curing . . . Castings will achieve maximum physical properties and better heat resistance if Crystal Clear is post cured.
Post curing is recommended if castings are thin or of low mass concentration. Castings should be post cured in a mold or
support structure. Post Cure Schedule: Allow the material to cure for 6-8 hours at room temperature followed by 6 hours at
150 – 160 F (65 – 72 C). Allow casting or part to cool to room temperature before demolding.
Materials should be stored and used in a warm environment (72° F / 22° C). Castings will reach ultimate physical properties
at room temperature in 5 – 7 days. Castings removed from mold before recommended cure may exhibit a tacky surface that
can be eliminated by exposing casting to 150 F / 65 C for 6 hours.
Casting Thickness & Cure Time – The cure time and ultimate shrinkage of all Crystal Clear products will vary depending
on mass concentration, thickness of the casting, mold configuration, etc. For example, a 200 gram mass of CC 200 will cure
faster if left to cure in a conical vessel (cup) versus a casting dispersed as a thin sheet measuring 3 centimeters square by
1 mm thick. This is due to the heat generated by the concentration of material in the cup versus heat that is dissipated from
the sheet casting. Castings will resist yellowing when exposed to UV, but may darken over time.