Post #215763 by Rum Demon on Sun, Feb 19, 2006 9:52 AM

Nice, explicit details. Was this your first mold or have you done it before? You're totally right about the part line being the majority of the labor. I think every mold maker has their own tools/methods for the "clay up". I bet it's much easier with a silicon master. When working on the part line one has to be VERY CAREFUL not to gouge the original sculpt, which for us is usually plasticene. We generally make the box out of foam-core AFTER buiding the clay up. This way we have easier access to the part line. I think I'm going to build a reuseable, adjustable box out of wood for future molds.

You skipped the step where you poured the plaster. Did you do a "splash coat" over the sculp first? After spritzing the sculp with water, we gently brush a small amount of the plaster in it's fairly liquid state over the exposed half of the piece first and gently brush it around, or if possible, lightly blow on it with compressed air. This is a good way of getting rid of any bubbles that may form. When we're happy with this, we then pour the rest of the plaster into the form. It's a bit tricky, especially if the plaster kicks quickly, but always works pretty well.

In addition to keys, we add pry points to our molds. That is, before pouring the second half, stick a couple of small wedges onto the mold, making sure they touch the sides of the box. These wedges in our case are usually just bits of clay. This leaves you with a place on the mold in which to stick a flat head screwdriver for leverage in getting it open. Very nice to have, especially when you open it for the first time.

I could go on with asking questions and imparting the bits that I know for hours. I'm really liking this thread. Thanks for all the pictures. I think this should take some of the mystery out of the process for people.

nice work,
Joe