how can i do large scale resin casting?

I am aiming to make a large resin sculpture, First of all, how can i make the mold? the original piece I want to duplicate is made from card board, it is about 4 feet by 4 feet, Could i put the cardboard piece in a tub and then spray expanding foam on it, also what would i put on the cardboard so the foam or what ever wouldn't stick?
would i next pour some sort of casting resin in to the mold?
Thanks very much

frithahobbs4 years ago
a little late for you but might help anyone else in the future: i'm casting polyester resin and after a few tests in small molds I will line a large (400mm x 850mm) mdf box with cellotape then mold release. I don't think the mold release is hugely crucial on top of the cellotape but I'm doing it anyway. The cellotape is going to give me a glassy smooth finish. Choose the right resin for large scale casts and you will probably need to do it in small increments so that heat does not build up.
RTV Steve6 years ago
Silicone might be best. It is liquid that turns to rubber. You would need Vaseline to make sure it does not stick to the cardboard. There are mold making free articles at www.RTVMoldMAking.com under freebies
NachoMahma6 years ago
> what would i put on the cardboard so the foam or what ever wouldn't stick?
.  Try searching for release agent and mold release agent.
+1 It will likely be some form of oil. A rubber or rubber-like goo can also be used to form the mold, although you'll still need to provide support beyond it to ensure that deformations in the final are kept to a minimum. Look for latex molding compunds