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Molding and Casting Group Assignment

Molding and casting products on hand:

Smooth-On

  • Safety Data Sheets (Oomoo, Smooth-Sil): Link

Oomoo (25 & 30)

1.2 part Tin-cured Silicon Rubber Mold Mix. The main difference in Oomoo 25 and Oomoo 30 is the pot life and cure time.

  • Oomoo 25: Hardness: 25A. Pot Life 15min. Cure 75min.

  • Oomoo 30: Hardness: 30A. Pot Life 30min. Cure 6hrs.

2.Short Shelf Life: The manufacturer states a shelf life of 9 months (from date of manufacture) at 23°C; 6 months at 27°C; and 2 months at 38°C. We live in a hot Caribbean country, so we lost allot of our stock to hardening (and thus becoming unusable) because of the heat.

3.Webpage Link

4.Product overview: Link

Smooth-Sil 940:

  • 2 part Platinum Silicon Mold Mix. Hardness: 40A. Pot life 30 min. Cure 24hrs.

  • Food Grade silicon. Mix needs to be poured over mold positive and placed in a vacuum chamber to remove all air from mold before it sets in order to be made food safe.

  • Shelf Life: 12 months at 23°C.

  • Website Link

  • Product Overview: Link

EpoxAcast 650 – w/EpoxAmite 101 (fast hardener) or w/EpoxAmite 102 (medium hardened)

  • Shelf Life 24 Months at 23°C.

  • SDS:

  • EpoxAcast 650: Link

  • EpoxAmite 101 Hardener: Link

  • EpoxAmite 102 Hardener: Link

  • Website: Link

  • Product Overview: Link

Plaster of Paris:

  • SDS:

  • Website Link

  • We used generic Plaster of Paris from our local hardware. It didn’t come with an SDS, but we found this SDS online for a particular brand.

Procedure:

We read the Safety Data Sheets for the above products that we used in our testing. Everything we used was designed for normal consumer and hobbyists use and is pretty safe to handle. Nothing stood out as particularly worrying from a safety standpoint.

Although our lab is fairly large, it is still an enclosed air conditioned space; Out of an abundance of caution we decided to mix our liquids and leave then to cure in an open area with full ventilation.

The most noteworthy thing about the mold making materials we have on hand was the short shelf life of the Smooth-On materials. This is not strictly a “safety” note in the storage section of SDS. The storage notes in the SDS simply says “store in a cool, dry, well ventilated place away from heat, direct sunlight…”. But cool is a relative term. We had to hunt for other documentation on the products websites to get information on their stated shelf life. We live in a hot country, so had we done proper research we might have picked a range of products that, although they might be a little more difficult to work with, would have given us a longer shelf life. Even from the same manufacturer (Smooth-On) the Oomoo product line is the easiest to work with (according to manufacturer) but has a much shorter shelf life, and we believe it is much more susceptible to spoilage being stored in a warmer environment than Smooth-On’s other products. Almost all of our Oomoo (Part A of the 2 part mix) hardened before being opened, where most of the Smooth-Sil and all of the EpoxAcast survived the same environment.

Pictures

  • Oomoo 30 cast

  • Smooth-Sil 940 cast

  • EpoxAcast cast

  • Cast of plaster of Paris.

Last update: November 28, 2023