No, the molds are silicone rubber, and the knob material is epoxy resin. Many hobby shops have these materials. You can reuse the molds 30 or 40 times before they start to go south on ya. Some of the molds pictured are for Sears (Arvin) metal radios, they are always missing.
Ya might start here:
http://www.hobbycast.net/video.htm
or here:
http://www.smooth-on.com/
or here:
http://www.alumilite.com/
or here:
http://www.sfjssantafe.com/
just google silicone rubber and you will be flooded with sources.
Same with the epoxy resin.

I made up some blank shafts coated with a release and plug them into the back of the knob after I pour it.
Denny Graham
Sandwich, IL


Denny G
Sandwich, IL