Need help with Resin casting project - Ice blades from anime Fairy Tales

[jardane]

I am making a cosplay prop and i need some help. It will be a large ice shard blade (images below) I was thinking of making a positive using foam then covering it with packing tape then release wax then resin coating it. That is my plan but there are several things that can go wrong. I plan on using acetone to melt the foam inside the Resin leaving a hollow resin shell but i am not sure if acetone also affects resin too. Most Resin is too thin for this and will just run off when i try to paint it on to an object. Is there any kind of resin that is thick enough to be painted on with a paint brush and not totally run off before it sets?

Am i going about this all wrong? is there a better way to get an hollow resin shell to look like the images below?

 

[HMS Mike]

You could do it in L200 foam construction and coat the inside with release and roto cast the inside. You could then do multipal coats inside to make it as thick as you would want.and peal the L200 off the cast. Or make a vacuum form mold.

 

[jardane]

I thought about doing a roto cast but it's a big prop and i would need to build a big roto frame to make it work. I could also build a vacuum form mold too and do it in pieces then glue it together.