| Deciding how much material is going to be needed when making a mold is important.
You certainly don't want to mix to much material nor make to little. Silicone is expensive, and if you pour to much it is wasteful, if you mix to little, your mold is worthless and wasteful.
Therefore an accurate account of what you are casting will help to determine what volume of silicone is needed to reproduce it.
So, you pour water into your mold form to fill the form (in my case, a desk drawer organizer). Then pour that same water into a measuring cup so that you can see how much your form can accept total.
This value should be your absolute maximum of material. THIS VALUE IS VERY IMPORTANT!
Now you know your absolute limit. This is the volume of the form WITHOUT any parts being molded!
Now you can submerge your parts to be molded into this cup of water. There are two things you need to remember - the water in the cup is now only being used to determine the displacement (volume) of the parts you wish to mold. Once you have done this however, your parts are going to absorb/saturate with water and draw some of the displacement numbers down (since the parts will not absorb nearly as much silicone). So you should measure quickly as well as measure freshly cast parts (they will obsorb less water and give a more accurate reading).
So you subtract your part volume(s) from the max volume and you have the volume of material needed to fill the form.
However, rarely would you need to fill the form unless your pieces are that tall, there fore you will need to do a little more measuring. You will want to pour in enough water into the form to be able to submerge the part with at least an 1/8th inch layer above - 1/4 inch would be best. Follow steps above to measure your part and liquid volume levels.
You will also want to add about 5% - 10% for the amount of material that will remain in you mixing vessel and on the mixer as well.
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