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10b. Molding and Casting (CLS Adults)

This week, our group was asked to review the safety data sheets for each of the molding and casting materials, then make and compare test casts with each of them.

The following shows the material we each researched in the Charlotte Latin School Fab Lab:

Task 3: Performance Urethane Casting Resin–Nidhie Task 8: Heat Resistant Urethane Plastic– Barbara Mold Star 31T: Platinum Silicone Rubber– Scott Liquid Plastic: Urethane 666–Charlie Smooth Cast 300Q–Avery

We did not find out (until much later) that we had “Dragon Skin 10 NV Silicone”. However, Barbara Morrow and Nidhie Dhiman used this material with their individual project molds and compared it to the Mold Star Silicone.

Material Pot Time Cure Time Viscosity Mixing Ratio (Part A: Part B) Special Notes
Dragon Skin Silicone 15 min 70 min low 1A:1B Very flimsy
Mold Star Silicone 5 min 23 min relatively low 1A:1B More durable
Task 3 Urethane Resin 2.5 min 10-15 min very low 1A:1B Moisture sensitive/absorbant
Task 8 Urethan Plastic 20 min 90 min low 1A:1B Produces exothermic reaction
Urethane 666 Plastic 7 min 30 min low 1A:1B Finicky– if mixed improperly
Smooth Cast 300 3 min 7-10 min low 1A:1B Bubble free and no de-gassing

The following video shows us all mixing each material’s Part A and Part B. (All of the materials we had in the Fab Lab had a mixing ratio of 1:1).


The first thing we did was spray eight batman and superman “chip” molds with “Ease Release-200”. We mixed equal amounts of Part A with Part B of each substance in a disposable cup, and mixed (gently and vigorously). We poured enough of the material into the mold to just reach the top (although some of them were over-poured). We allowed the materials to cure for the next three hours and examined them, noting characteristics of each substance.


One of the biggest things to note is the fact that the Task 3 Resin seemed to be outdated as it foamed. We thought at first that we didn’t mix it well, and we redid it. The same thing happened when we repeated it. When we left that night, the Task 8 resin bubbled up. (The bubbles were not present when we left for the night). Within the eight hours we were gone, it not only bubbled in the center, but it also darkened in color.

Link to Files/Datasheets

Last update: May 24, 2022