In our studio, mold making is part of our program. We use two
For molding models which can survive 307 degrees and lots of
pressure, as in vulcanizing, we prefer to do it that way. Most of
our metal “masters” are molded this way. “No-shrink” mold rubber
sheets work well, and molds are quick to make (1/2 hr heating time in
the vulcanizer for small molds).
For models which won’t take heat or pressure, we use a room-temp mold
compound which takes much longer to set up and cure (overnight), but
provides great detail and minimal shrinkage. Models can be of
absolutely any material, and parts can be glued with anything or
stuck together with wax, if you want. The liquid mold compound is
quite gentle with models, and will not disturb delicate patinas or
finishes. Antique carved ivory, as an example, is unaffected by this
type of molding, and molds well.
Companies which sell the room-temp curing mold rubber have varying
degrees of “durometer” or stiffness, so that aspect of the mold’s
character can be adjusted from batch to batch, if desired, by just
ordering a higher or lower durometer of the liquid mold compound and
catalyst. One nice part of making room temperature molds is that you
can make your own “U” shaped mold forms out of wood, and clear
plexiglass “windows” for each side. These mold forms have an open
top, and the thickness, width, and height are easy to make in wood.
We use wide masking tape to hold the frame and plexiglass together,
and then vacuum the liquid mold compound under a bell jar to get the
bubbles out. A pretty simple process, especially if you have a
vacuum casting machine.