Crystal Clear™ 204

Crystal Clear™ 204 *NOTE: Product Packaging May Vary

Technical Bulletin and SDS

Crystal Clear™ 204 is a water white clear and made specifically for applications that require clarity. These rigid urethane casting resins differ only in working and demold times. Low viscosity ensures easy mixing and pouring. Crystal Clear™ resins cure at room temperature* with negligible shrinkage.

CAUTION: NOT FOR HOME USE. THIS PRODUCT IS FOR INDUSTRIAL USE ONLY. With adequate local exhaust ventilation, respiratory protection is not normally required when using this product. Where risk assessment shows air-purifying respirators are appropriate, follow OSHA respirator regulations and European Standards EN 141, 143 and 371. Protective clothing (gloves and long sleeves) is required to minimize the risk of dermal sensitization. If breathing is affected or a dermal rash develops, immediately cease using this product and seek medical attention. Read SDS before using.


Cured castings are:

  • UV Resistant
  • Not brittle

Vibrant colors and color effects are achieved by adding pigment dispersions.

Applications include:

  • Encapsulation
  • Making prototype models
  • Lenses
  • Sculpture reproductions
  • Decorative cast pieces
  • Jewelry
  • Prototype models
  • Special effects
  • Props

Click here for more Crystal Clear™ resin products.


Safety - Store and use at room temperature (73°F/23°C). These products have a limited shelf life and should be used as soon as possible. Environmental humidity should be as low as possible. Good room size ventilation is essential. Wear safety glasses, long sleeves and rubber gloves to minimize contamination risk. Wearing a NIOSH approved respirator will minimize inhalation of residual fumes. Use in a low humidity environment (below 50% RH). Mixing containers should have straight sides and a flat bottom. Mixing sticks should be flat and stiff with defined edges for scraping the sides and bottom of your mixing container.

Selecting A Mold Rubber - Pour into a urethane rubber mold (Vytaflex™ urethane or Brush-On™ series urethane – release agent required), tin cured silicone mold such as Mold Max™ 20, 25, 30 or Mold Max™ STROKE (not Mold Max™ ‘T’ Series) or Mold Star™ 15, 16 or 30 platinum cured silicone (not Mold Star™ ‘T’ Series). Do not use other rubber mold products.

If using Mold Max™ silicone; to prevent cure inhibition, post-cure newly cured silicone mold for 8 hours at 150° F / 60° C and let cool prior to casting resin. If you are unsure about surface compatibility, a small scale trial casting should be made.

For Best Results Before Pouring Crystal Clear™ Into Mold: Pre-heat rubber mold at 212°F / 100°C for 4 hours. This will minimize chances of fish-eyeing, suck back, corner rounding, large bubbles, etc. in finished casting.

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 Crystal Clear™ 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.

  • Crystal Clear™ 200 is intended for a casting thickness ranging from ½” to 3” at a casting weight maximum of 16 lbs. (7.25 kgs.) Castings greater than 3” should be layer cast.
  • Crystal Clear™ 202 is intended for casting in thin sections. Developed for casting thicknesses of no more than ½”.
  • Crystal Clear™ 204 can be cast in thicknesses up to 6” at a casting weight maximum of 35 lbs. (15.88 kgs.).
  • Crystal Clear™ 206 is for castings greater than 6”. Crystal Clear™ 206 castings greater than 1/2” (1 cm) can be demolded after 48 hours and left to fully cure outside the mold. Castings less than 1/2” (1 cm) should be left to cure in the mold for 7 days.


Liquid urethanes are moisture sensitive and will absorb atmospheric moisture. Mixing tools and containers should be clean and made of metal or plastic. Materials should be stored and used in a warm environment (73°F/23°C). Stir or shake Part B thoroughly before dispensing.

Measuring - Materials should be stored and used at room temperature (73°F / 23°C). The proper mixing ratio is 100A:90B by weight. You must use an accurate digital gram scale to weigh Parts A and B properly. Do not use an analog scale or attempt to measure components by volume. Dispense the required amount of Part A into a mixing container. Weigh out the appropriate amount of Part B and combine with Part A.

Mixing - Mix SLOWLY, but thoroughly, for at least 90 seconds making sure that you scrape the sides and bottom of your container several times. If coloring or filling Crystal Clear™ product, add filler or pigment dispersion to Part B and mix thoroughly before adding Part A.

Bubbles in the finished casting will be greatly reduced by vacuum degassing prior to pouring. Your vacuum pump must pull a minimum of 29 inches of mercury (or 1 Bar / 100 KPa). Leave enough room in container for material expansion. Vacuum material until it rises, breaks and falls. Vacuum for 1 minute after material falls.


Pouring - If casting Crystal Clear™ into a rubber mold, pour mixture in a single spot at the lowest point of the mold. If encapsulating an object, do not pour the mixture directly over the object. Let the mixture seek its level. A uniform flow will help minimize entrapped air.

For Best Results: Bubble elimination is best achieved by pressure casting. After pouring the mixed compound, the entire casting assembly (mold, dam structure, etc.) is placed in a pressure chamber and subjected to 60 PSI (4.2 kg/cm2) air pressure for full cure time prior to heat curing.

Castings will reach ultimate physical properties at room temperature in 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. Pot life and cure time depend on mass concentration and mold configuration.

Post Curing - Castings will achieve maximum physical properties, better heat and UV 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 fully at room temperature followed by 6 hours at 150°F–160°F (65°C–72°C). Allow casting or part to cool to room temperature before demolding.

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.

IMPORTANT: Shelf life of product is reduced after opening. Remaining product should be used as soon as possible. Immediately replacing the lids on both containers after dispensing product will help prolong the shelf life of the unused product. XTEND-IT™ Dry Gas Blanket (available from Smooth-On) will significantly prolong the shelf life of unused liquid urethane products.

Related Categories: Urethane Resins

Related Series: Crystal Clear™ Series – Water Clear and UV Resistant