Composimold

Back on the topic of casting I heard about this reusable mold material called composimold. It comes in this natty plastic tub.

The jelly like blob on the right is the stuff after it was melted and poured into a plastic container. So what you are supposed to do is

Put the item(s) you want to cast in a container
Cover with a releasing agent (i.e. canola oil)
Heat the composimold and then pour over the items
Leave to cool
Use a knife to cut the mold and release the item
Tape up the mold, pour in some more releasing agent
Pour in you casting material (i.e. plaster of paris
Allow to dry
Release from mold and admire

Simple, eh? Well I can already add a few tips to that list. First off you should tape or glue the items down before covering with composimold otherwise they move around or just float to the surface. Which is entertaining to watch but not really the desired effect.

Also the plaster should be mixed a little thinner than usual so that it pours nicely into all of those cracks. Especially if you pick a small detailed model like a 4cm tall Dr Who’s Tardis. (Yes, the same one of stop motion video fame.)

As usual for a first attempt it’s not that great. The one on the right was using the thinner plaster which I think is slightly better than the one on the left. Also the plaster isn’t that great for fine detail. You can buy polyester resin which may work better but I haven’t found a cheap source of that. Also I have heard of some problems since the resin sets in an exothermic reaction (i.e. it gets hot) and it melts the composimold.

Practise makes perfect.