This is Alumilite's basic silicone rubber product for casting molds. It's intended to be used for casting with Alumilite's resins, see the standard resin for example Alumilite Super Plastic Casting Resin 28 oz..
This silicone rubber has a low tear strength, meaning that it's fairly stiff and creates pretty strong and firm molds. It's great for two part molds that need to be stiff for the two parts to line up against each other precisely. For making two piece molds, you will need a mold release agent Universal Mold Release by Aluminite Corp so that your two parts don't stick together. Make sure the first part of your mold is properly cured before applying the mold release and creating the second part. The rigidity does not make this silicone particularly good for complex molds with undercuts and deep parts, etc. that will be difficult to demold and you could end up damaging your mold. For those types of castings, use Alumilite High Strength 3 RTV Mold Making Rubber 1 lb. HSIII RTV which is very flexible, stretchy and does not tear easily.
The product has two parts, the base and a catalyst that are mixed in a 10:1 ratio by weight. The product comes with mixing containers that will help you mix the two parts. However, it's much better to get a scale, particularly one that measures in tenths of a gram or tenths of an ounce. This will be particularly important when making small molds for detailed parts when only a little of the catalyst is needed. We use American Weigh BLADE-600BL Blade 600G X 0.1G Digital Pocket Jewelry Scale Blue, which is both inexpensive, small and pretty accurate.
Once the two parts are combined, mix until no swirls of other colors are seen. Vacuum chamber will help remove the bubbles but it's not necessary. We've found that pouring in small increments helps eliminate bubbles. That is, we pour up to a 1/4 of an inch of the mixture into the mold and then wait for any air bubbles to surface and lightly blow on them to pop them. Once this layer of silicone is bubble free, we pour in another 1/4 inch or so and repeat the process until we're done. The silicone mixture has up to 30 minutes of open time for mixing and pouring so you have some time.
The mixture will make a perfect imprint of whatever piece you're making a mold of. It is great and will pickup even the smallest details and scratches, prints, lettering, etc. We created a mold of an N-scale shipping container and all the signs, labels, etc. showed up on the pieces we later cast into the mold. It's pretty impressive pickup of details.
For making a box for your mold, we've used Lego pieces, cardboard, or scraps of foam board. We typically put our mold box on a piece of styrene to get a clean flat surface and either use Alumilite's putty or hot glue gun to keep it all in place. Also, the manufacturer has a number of how-to videos on their website.
In summary, this is a great product that allows you to create your own molds for small and medium size things and then cast numerous replicas.
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