How to Calculate Material Volumes
Many of us just guess the amounts of mold making and casting materials needed for a project. But in guessing we are very seldom right. We either under mix or over mix our materials. Over mixing means waste. Under mixing means more work or worse we don’t have enough stock and we are caught short. Yet a mold maker can easily calculate the amount of silicone, resin or gypsum plaster materials needed down to a fraction of a gram. Here’s how:
Please view the video above for an explanation of tip and tricks in how to make more exacting material requirements.
You can use the calculator section of this page above, to determine the exact quantities of mold making or casting materials needed. Just make the measurements and then plug in the sizes of your mold container and model into the appropriate box on this page. Then click calculate. It will do all the work for you.
For those who prefer the written word, here is a short explanation of the procedures.
Make a note of the volume constants:
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Silicone Rubber: 0.740 ounces per cubic inch.21 grams (453 grams per pound).
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Polyurethane Resin: 0.544 ounces per cubic inch
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Gypsum Plaster: 0.490 ounces per cubic inch
To find the volume of mold making or casting material you must first calculate the volume of the mold container and then the volume of the model or pattern you are casting. Then just subtract the pattern volume from the mold container volume. That is all there is to it.
For a square or a rectangle, the volume = length x width x height
For a cylinder or tube shape, the volume = π (3.14) x radius squared x height
Those two formulas will provide the volumes of the mold container and the model or pattern being molded or cast.
Once you have obtained the volumes in cubic inches, multiply by the constants above (depending on the material you are using) to determine the weight of fluid ounces.