Fetal Deep One Moldmaking and Casting 03

By the next day the molds have cured. The main mold of the body needs one more step before we can begin work on the other side. We need to get this sides half of the mother mold  shell on. The clay retaining wall for the silicone has been removed and the silicone trimmed to provide a clean edge. Another retaining wall is built a bit further out from the silicone. This one is for the mother mold. This will be a jacket to support the silicone mold.




The mother mold material applied to the main body mold. The material for the mother mold acts like cake frosting and sets up quickly.



A few hours later, i pried the clay platform up from the board and flipped it over. You can see the rapid build of the platform with chunks of clay from this side. The other side of the model is revealed.


And voila! One half is done. You can see the model couched in the silicone which in turn sits in the mother mold.


The process now begins again. A clay retaining wall for the silicone is put up.



The little clay boxes that contained the arms and legs were broken down and the walls reused to quickly build up new boxes to be able to do the second silicone pour. You can see the little buttons on the surface. These were the dimples from the first part. The sprues, those little conical towers, are buried in the silicone matrix. These are examples of block molds. When i use these, a couple of rubber bands will be all i use to hold the halves together.


The pouring of the silicone for the second sides is a two step process. The first silicone layer is put down thin to avoid bubbles and to make sure all the surface detail is captured. After the silicone becomes tacky, in about an hour, a second batch is poured into the small molds. The larger model model has a thickened silicone applied so that a shape can be generated instead of having the liquid just run down to the lowest areas leaving all the high points without enough coverage. This all needs to sit overnight again.