Molding and Casting#
This week’s group assignment is designed to familiarize ourselves with the the molding and casting materials we will be using.
- Review the safety data sheets for each of your molding and casting materials,
- Make and compare test casts with each of them.
The Material Line-up#
As part of the FabAcademy inventory, we have access to two different types of molding materials and two different types of casting materials, all by Smooth On.
The Smooth-On Document Library holds all the Technical Bulletins and Safety Data Sheets of their products.
- Mold Star 16 FAST (Platinum silicone)↗︎
- SORTA-Clear 37 (Water white translucent silicone)↗︎
- Smooth-Cast 300 (Ultra-low viscosity casting resin)↗︎
- Smooth-Cast 325 (ColorMatch Series plastics are urethane resin)↗︎
A quick comparison of the main features:#
| type | Mold Star 16 | SORTA-Clear 37 | Smooth-Cast 300 | Smooth-Cast 325 |
|---|---|---|---|---|
| Color | Blue | Water Clear Translucent | White | Clear-ish Amber |
| Pot Life | 6min | 25min | 3min | 2.5min |
| Cure Time | 30min | 4hours | 10min | 10min |
| Mix Ratio(Volume) | 1A:1B | 1A:1B | 1A:1B | 1A:1B |
| Mix Ratio(Weight) | 1A:1B | 1A:1B | 10A:9B | 115A:100B |
Stirring and Bubbles#
The 2-part materials need to be mixed properly, if that is not the case, they will not work as expected. The problem is, that stirring introduces air-bubbles. This creates a challenges, especially if the pot time is in the range of 3 min. Mix, stir, pour, de-gas (if available). Too fast, air bubbles. Too slow, materials starts to hardens.
The Safety Data Overview#
The safety data for the molding and casting material is basically the same-
- Wear protective clothing, gloves and glasses, so that the material does not touch your skin.
- Don’t eat or drink it. Don’t eat or drink anything in the working area.
- If swallowed, do not trigger nausea, call a doctor.
- Ventilate. Don’t inhale.
- Don’t do anything stupid with the material.
Test Casts#
For test casts we could either use normal plastic cups, empty PET bottles. Or we could go to the ¥100 shop and get some character silicon molds. We did the later.
We measured an poured all 4 materials, we introduced air bubbles on purpose and did not use the vacuum chamber to reduce the bubbles. (Thank you @Rico for borrowing the vacuum chamber).
Results are mixed.
But pretty and nice and かわいい。
What we learned: Do not cast silicon in silicon. It will be difficult to remove and some details will get lost when peeling.