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The Dübendorf Brothers

Making the silicone molds

Some materials are necessary to make silicone molds and cast resin. Here is a basic list: silicone with curing agent, plastiline, two component epoxy resin, double sided tape, styrofoam, sculpting tools and, of course, the parts to be molded (picture 12). A digital kitchen scale can prove useful when you use silicone and resin as it allows you to mix the components very precisely.

I decided to make the main part's mold in two pieces. It is important to plan ahead when you work with silicone and resin as all decisions will have a direct impact on the final product's quality. I first used pieces of styrofoam secured with double side tape to make a small box (picture 13A). This is a pretty straightforward and fast method, much more easy than making a box out of wood. The bottom of the box is made of plastiline and the part to be molded is half embedded inside. The holes were made to allow the two halves of the mold to go together precisely later. The trench around the part is to prevent resin flow between the mold. Once the box was finished, I mixed some silicone using my digital kitchen scale and applied some on the part using a small brush (picture 13B). This is to avoid bubbles forming at the most inappropriate places. Then the remaining silicone was poured in until nothing was visible anymore (picture 13CD). The double side tape acted like a hermetic seal and no silicone escaped. Now the big wait began and at least 24 hours were necessary to let the liquid mass become solid.

The day after, I took away the plastiline (picture 14A) and a nice negative form appeared (picture 14B). I applied some varnish (on the silicone only) and poured the second half of the mold (picture 14C) until, once again, everything disappeared. After another 24 hour curing period I broke the styrofoam box and the final result was a big silicone block (picture 14D). Now you would think is the time to free the part to see if the whole process was successful? The answer is NO! Before doing this, it is always necessary to make a solid hull (in this case plaster) around the mold (picture 15AB). Without it, the molds would not remain together while pouring the resin and it would end in a big mess! The final result can be seen in picture 15C. You can also see the pouring hole cut out of the silicone with an X-acto knife. Again, I used my digital kitchen scale to mix the resin components precisely (picture 15D).

For the detail parts I used almost the same technique as the main part (picture 16 and 17) with the difference that the resin can be poured directly in the form from the top, the second silicone part acting like a cover (picture 18). The result is a resin wafer including all the detail parts altogether. This technique is only effective for small parts of course. In picture 19 you can see the resulting resin parts in their rough state and now it is possible to go into mass production! (Picture 20)