I have built two puppets that use poly foam sheets as the structure for the head and torso. Would like to know how expandable soft urethane foam compares to the soft sheet foam as far as durability and ability to keep its shape and anything else that matters. I can form the look I want with clay first and make a mold. If I use expandable foam, how well would it look without a covering or skin? Also, what brand and weight/density expandable foam do you recommend?
Thanks, Kevin

Expanding foam is fairly dense, I would think it would hold up fairly well. I don't think I would want to use more than 2 lbs/cu. ft. just for the weight issue. You can always add a coloring agent to the liquid foam to get the color you want, or you could go all out and put down a skin layer first, and then add the foam.