What material can i make my sculpture out of?

I need to make a sculpture for my architecture cl. I would like a material that i can melt, shape into a volume, and sculpt it. thing is it has to be clear so i can be able to put things in it or that i can make a gradient from it from side to side. I already researched glycerin (raw material for soap) but that is pretty expensive, Any help??? Thanks in Advance