Wasteland wrote:I work as a caster. I would recommend trying out some of the casting products that are designed to work without pressure or vacuum first, just to get a feel for how the process works. However, you won't get results as good as you would with production-grade materials. This can be fine! If this is intended as a hobby project and you're not making lots of casts, you can substitute time in place of money and equipment - your casts may not come out of the mold as professional-quality pieces, but nearly all the problems this creates can be fixed with putty, sanding and patience. Smooth-On sells starter kit with OOMOO silicon that's designed to be easy to work with without specialized equipment.

If you're being more ambitious, high-quality casts usually require some specialized equipment to produce. The process I use is much like the one used by companies such as Forge World. I use Smooth-On Mold-Max 20 silicone and Smooth-Cast 305 polyurethane resin, and ER200 mold release.

In order to avoid bubbles or voids in your finished product, the resin needs to cure under pressure. This is done using a pressure pot - a sealed vessel that you place filled molds into, then seal and pressurize with an air compressor to about 45-60 PSI. Most are adapted from industrial spray paint tanks. A new one will usually cost about $150-200.

In order to make your own molds, you'll also need a way to de-gas the liquid silicone after it's mixed. This requires a vacuum chamber to pull the trapped air out of the silicone so you have a void-free mold that will work when pressure casting. While these can cost upwards of $300-400, you'll only be using it for a minute or two each time you pour molds. If you're not starting your own casting business, owning your own is usually overkill. See if there are any local manufacturers or maker spaces that might have one you can use.


As a general rule, pick a slower-curing resin (305 is the slowest of the regular 300 series). This gives you more time to work, produces less heat when curing and is gentler on your molds.

You'll want to start out by doing at least a few simpler 1-part molds (parts that end up flat on the back) to build up your experience before tackling a more complex project with 2-part molds. There's lots of great information available online, but a lot of this can only be learned through practice.

Good luck!