Plastic corn halves coated with release
What we have here are fake corn cobs, made of plastic. They are sliced
exactly in half down their parting line, and then nailed to a piece of
melamine shelving. A chemical called PVA (poly vinyl alcohol) has been
brushed on to act as a mold release for the fiberglass resin.The whole idea here is to make a pattern for an aluminum corn-cob
making mold. The finished aluminum piece that this pattern will produce
will be used for casting epoxy replicas of…you guessed it, corn cobs.
It’s a “mold to make a mold” project!
On an earlier attempt, I had used just resin and cloth against the
corn-kernel surface. This resulted in a lot of trapped air, and big
ugly voids. So as you can see in the picture, I smeared the cobs with
bondo to help fill in between the kernels to make a better imprint. It
Now, on top of the bondo, I’m putting about 3 layers of fiberglass
cloth and resin, tucking it neatly down between the cobs. I used
aluminum duct sealer tape to form a dam to hold in the resin, which I
poured to about a quarter inch (7mm) thick.
The PVA mold release now officially has my utmost respect. The mold
pulled free of the melamine, and the corn cobs pulled very neatly out
of the Bondoed cavities.
I used the bottom of a paint can to draw the radii of the corners, then
cut out the whole pattern with a band saw. The tab at the right end
will be drilled and used for hanging the corn molds on a pegboard hook
There were still a few air bubbles in the resin, so I filled them in with Bondo putty as well, then sanded them down smooth.
I always paint my patterns with the obligatory “Dan’s
Workshop-dot-com-gray” paint (most accurately color matched of course),
acquired from my local Home Depot.Painting the patterns helps to spot any blemishes that might have
gotten missed. It also makes a nice slick finish for the molding sand
to release from. Stay tuned!