There's more than one way to make a resin. Some people use a roto-caster, which results in a lightweight, hollow cast model. Jennifer Scott prefers to use an air compressor and pressure tank (also called a pressure pot or casting pot). The filled mold is placed inside the pot, and the pot is closed. The air compressor forces air into the pot, which shrinks the air bubbles in the liquid resin to microscopic proportions. This creates a solid cast, but extremely clean model with no pin holes.Jenn's resin of choice is Smooth-Cast 305. She likes it for its whiteness, strength, sandability and seven minute pot life. She used to use Smooth-Cast 300, which has a two min pot life, but she prefers having more time to mix, pour, fasten and fill the tank. Trying to do all that in just two minutes was crazy and stressful!
Different resins have different mix ratios, but Smooth-Cast 305 is 1:1 of Part A and B. Jenn likes to "cross the streams" as she pours for added mixing. As soon as the two parts combine, the clock starts ticking!
Mix very thoroughly...
and then it's time to pour. Because she's pressure casting, she doesn't have to worry about degassing the resin or pouring in a slow, thin stream.
This particular mold uses a hind leg for a pour hole.You can see the other hind leg's air vent at the bottom of the photo.
When the mold is filled with resin, it's pushed back into the pot and the lid is fastened via the wing nuts. Everything must be good and tight before you start letting air into the tank.
Pressure casting requires at least thirty psi of pressure to work, but sixty psi is ideal. Jenn's tank tank is rated for up to eighty psi, but since there's no quality difference between sixty and eighty, she uses the lower setting.It's better to mix too much resin than too little. However, resin is expensive, so Jenn pours the excess in a small medallion mold.
These will be wonderful live show prizes!
The mold will stay inside the pressurized tank for approximately forty minutes, so there's lots of time to cuddle Jenn's studio helper while waiting for the new arrival.
The third and final part of this series will cover removing the new resin from the mold and basic clean-up. Thanks again to Jennifer Scott for making these posts possible!