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9. Molding and casting – Group Kuriyama

This is group assignment page of Computer-controlled cutting (Kuriyama Student) :

Group assignment

  • review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them

What we’ve done this week

  • SORTA clear 37

  • Smooth-Cast® 300

SORTA clear 37

Reference pages:

Safety First!

  • Wear the eye protection
  • Wear the hand graves
  • Flush eyes with water for 15 minutes and seek immediate medical attention if contact with eyes.


  • Color: Water Clear Translucent
  • Pot Life: 25 minutes
  • Cure Time: 4 hours
  • Mix Ratio: 1A:1B by volume
  • Safety: food safe, non-hazzordous
  • Baking mold under 204℃

How to use


  • Pre-mix Part B thoroughly.
  • Dispense the required 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 time
  • Vacuum degassing is recommended to eliminate any entrapped air. Vacuum material for 2-3 minutes (29 inches of mercury), making sure that you leave enough room in container for product volume expansion.


  • 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.


  • Allow the material to cure fully at room temperature (73°F / 23°C) before demolding. SORTA-Clear™ 37 cures in 4 hours. Do not cure rubber where temperature is less than 65°F / 18°C.
  • Post curing the mold will aid in quickly attaining maximum physical and performance properties. After curing at room temperature, expose the rubber to 176° F / 80° C for 2 hours and 212° F / 100° C for one hour. Allow mold to cool to room temperature before using. IMPORTANT: Rubber will darken considerably when exposed to heat.


  • Time to demold can be reduced with mild heat. IMPORTANT: Rubber will darken considerably when exposed to heat. Note: Allow mold to cool to room temperature before handling.

Using The Mold

  • New silicone rubber molds exhibit natural release characteristics. Depending on what is being cast into the mold, mold lubricity may be depleted over time and parts will begin to stick. No release agent is necessary when casting wax or gypsum. Applying a release agent such as Ease Release™ 200 (available from Smooth-On) prior to casting polyurethane, polyester and epoxy resins is recommended to maximize mold life.

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 can 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.

Disposal method in my town (Kuriyama, Hokkaido, Japan)

  • Garbage that can’t be burned to ash

Smooth-Cast® 300

The Smooth-Cast™ 300 Series of liquid plastics are ultra-low viscosity casting resins that yield castings that are bright white and virtually bubble free. Vacuum degassing is not necessary. They offer the convenience of a 1A:1B by volume or 100A:90B by weight mix ratio. The differences between them are pot life and demold time.

These resins readily accept fillers (such as URE-FIL™ 3 from Smooth-On) and can be colored with SO-Strong™, UVO™ or Ignite™ color tints (Smooth-Cast™ 325 series accepts pigments better than the Smooth Cast™ 300 series). Fully cured castings are tough, durable, machinable and paintable. They resist moisture and mild solvents. Applications for Smooth-Cast™ 300 Series Liquid Plastics include reproducing small to medium size sculptures, making prototype models, special effect props and decorative jewelry.


  • Safety

    • Wear safety glasses, long sleeves and rubber gloves to minimize contamination risk. Use only in a well-ventilated area
  • Preparation

    • These products have a limited shelf life and should be used as soon as possible. Materials should be stored and used in a warm environment (73°F/23°C).
  • Applying a Release Agent

    • A release agent is necessary to facilitate demolding when casting into or over most surfaces.
  • Pouring

    • Pour your mixture in a single spot at the lowest point of the containment field and let the mixture seek its level. This will help minimize air entrapment.
  • Curing

    • Use this product with at least room size ventilation or in proximity to a forced outlet air vent and do not inhale/breathe fumes. Fumes, which may be visible with a significant mass concentration, will quickly dissipate with adequate ventilation.
  • Post Cure

    • Castings will reach “full cure” faster and achieve maximum physical properties if post cured.
  • Performance

    • Cured castings are rigid and durable. They resist moisture, moderate heat, solvents, dilute acids and can be machined, primed/painted or bonded to other surfaces (any release agent must be removed).
  • Disposal method in my town (Kuriyama, Hokkaido, Japan)

    • Garbage that can’t be burned to ash
  • Test

I added 10 g each of PartA and PartB.

As soon as I mix it, it began to get hot.

After 5 minutes, it turned white in color and hardened.

We found that when using the mixture for individual assignments, it needed to be poured in immediately after mixing because it hardened quickly.


Last update: March 28, 2022