Enter Your Reply

Hi, Gary:  If you say it works, I'll take your word for it; I've seen
some of your artwork, and am not surprised that you get professional type
results with little sculptures:-) Sometimes hard molds are all you need,
and if you can do hand-finishing, well, okay.
I usually use a pourable silicon rubber for most molds, a rather pricy
specialized stuff, but the window-caulk works fine for a semi-stiff, tough
flexible mold, the advantage of which is the ability to make tricky
undercuts and highly detailed surfaces, and ease of removal when
demolding.
For a 2-piece mold:
1. Lay the pattern on its side on a small, clean work-board, and build a
vertical plastalene wall which covers the bottom of the pattern and
creates a flat area all the way around it for at least an inch.
2. Use Klean-Klay (sulfur-free, commonly available oil-based plastalene
clay, never dries or hardens) to build an area of 'land' around the
pattern, using a small knife to dress the edge up to the side of the
pattern at a clean right angle where you want the parting line to be.
3. Use a blunt tool to make a 'ditch' in the area of 'land' around the
pattern, or push a few shallow holes into it; these will register the two
halves of the mold into alignment.
4. Brush-apply the silicon all over the pattern and the land; let dry and
repeat until at least 1/8-in. thick all over.
5. When dry, mix a small amount of plaster and make a 'mother' mold on
top of the rubber; mix it thick enough to not be runny, but be quick
laying it on, maybe a half-inch thick.
6. When the plaster piece is set, flip the whole rig over and carefully
remove the plastalene clay, revealing the pattern, now buried halfway in
the rubber, and clean the area well with a small knife.
7. With a small brush, very lightly coat the exposed rubber with vaseline,
then do the other half of the rubber, just like the first half
8. When dry, make another plaster, right on top of the rubber; you now
have a sandwich of plaster, rubber, (pattern), rubber, plaster.
9. Remove plaster housings and gently peel the two rubber pieces apart,
completely or only down one side, if you like, and remove the original
pattern.  Now you have a mold that you can cast almost anything into, many
times. Reassemble for pouring and rubber band around to hold it together as
you pour into the exposed hole made in step 1.