How To Handle Large Undercuts In The Brush‑On Mold Making Process

Here is the plaster 3-D model to be molded using the brush-on process. As you can see in the back views, there are 2 large undercut areas under the shoulders. Examine the model carefully, and develop a plan of attack before you apply rubber or a support shell. Minimizing undercuts now means an easier demold later. Draw parting lines to help identify individual support shell segments. Parting lines also help identify the cutting line for mold rubber.

Optional technique: use modeling clay to define the outer flange edge. Secure the model to the base with hot glue gun and apply SuperSeal® sealing agent. SuperSeal® does not alter surface detail.

Apply Universal® mold release.