I was just surfing around and found a very old thread where someone mentioned seeing something about Sand being added to epoxy and then that being spread on as a build up for molds. The thickened concoction was called 'mud'. Anybody hear about this? There was a link to a very old thread here but its not working. Here's the link to the thread I found...
http://www.rcuniverse.com/forum/comp...2337-sand.html