|There are several topics to consider when deciding to use Body Double® silicone or Alja-Safe® alginate:
1. Mold Life - Alja-Safe is suitable for making molds intended for short-term use, typically 1 - 2 castings. Body Double on the other hand is frequently used because it is a "library life" mold making material. Molds made of Body Double silicone rubber can literally last for years and yield dozens of castings out of the same mold.
2. Casting Medium - Alja-Safe has limitations for what can be cast into the mold due to the fact that it is a water-based material. For the most part, only gypsum-based materials or very fast-setting polyurethane resins may be used successfully in an Alja-Safe mold. Body Double silicone rubber does not contain any moisture and therefore can accept many different types of casting media, many of which heat up during the cure process.
3. Tear Strength - Alja-Safe molds have relatively low tear strength, which limits how far they can be stretched before ripping apart. Body Double silicone rubber can stretch 6 times its original shape before tearing. 4. Shrinkage - As an Alja-Safe mold begins to dry out, it will shrink and deteriorate quickly. A Body Double mold will never shrink.
5. Cost - Alja-Safe alginate costs much less than Body Double silicone rubber.
6. Release - Alja-Safe alginate does not stick to anything. You don't need a release cream for most applications. You can make a mold of the hair on your head with alginate by using hair conditioner as a release agent. You can't make of mold of the hair on your head with Body Double. The best you can do is make a mold using a plastic bald cap.
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