this is random [ as I havent actually molded anything yet! XD ] but I'm a sculpture student, and have used something called Aqua Resin to re-enforce certain things and it is exactly like most resins but TOTALLY safe and water based, you can get it on your skin, breathe around it ect. It comes out very light weight yet supposedly? you can toss cured aqua resin out a 2 story window and it would be undamaged [ I've never tried]. The only draw back is its expensive. Like really expensive, I dont quite remember since its been a while. It's def,. something to look into though. Also the good news is that the reason is it's so expensive is because it's relatively new and is only made by one company right now, but that will probably change as it phases out all other resins.