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Mold Making and Resin Casting

Once this is done put up one wall of your box. Seal it to the base using hot glue. Repeat this all the way around the subject until you have your completed mold box, using hot glue at the corners and at the base (Fig 15). Then seal the clay where it meets the walls. I have found that the rounded end of a paintbrush works best. If you have any gaps here, break off small chunks of clay and press them in using the brush or your flat scraping tool.

Many people build their mold boxes before they embed their subject but I build them a side at a time. The reason I do this? I have found that it is easier to work the clay bed and gives you better access to the sides of your prototype to make sure you have a good clay to prototype seal.

The next step is to make dimples all the way around your clay bed. Use two different size brush ends to make these, making sure not to get too close to your prototype. Make the dimples about 1/4" deep (Fig 16). These dimples will become keys after the silicone is poured and will help lock your mold halves together when making a resin pour (Fig 17).

I usually run a bead of hot glue up each corner of the mold box from the clay bed to seal this area.

That is it. You are now ready to pour your silicone! You can use the same method to figure out how much silicone to use as earlier. Once you have done this for a while, you will start developing a feel for how much silicone to mix. If you are a little short, don't panic. Silicone bonds to itself so it is a simple matter of mixing some more and pouring right over the top of your cured or uncured silicone. I have run completely out of RTV and have had a part sitting half molded for a week and it comes out fine once you finish the pour.

Again, you can use the same process discussed in the single part mold section to measure out your silicone.

Mix in the same manner described earlier and pour (Fig 18 and Fig 19)
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  • fig16
  • fig17
  • fig18
  • fig19
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