This instructable shows how to modify and use a pressure paint tank for pressure casting. This is mainly useful for achieving bubble-free transparent or translucent resin/urethane casting effects.
The first step involves modification of a low-cost paint tank and the following section depicts the pressure casting process. I assume you have a mold (here is a great instructable on making a mold and video on making a simple block mold like I'm using below) and have basic knowledge of casting.
A professional 5-gallon pressure chamber costs upwards of $700, not including the compressor. A modified paint tank should cost under $120, and of course you will still need an air compressor.
You will need:
in addition to the mold (ideally free of air-bubbles), casting material, and a release agent.
Note: the gallery image shows two casts of the same material (Smooth On's popular 325 urethane plastic), one that was pressurized and another that was not. I used the exact same mold and process for each cast except for pressurizing the first cast.