Review on Sculpey III 10 Classic Colors Polymer Oven-Bake Clay 1.25 lbs. Non Toxic - Ideal for Modeling, Sculpting, DIY, School Projects, and Holiday Crafts. Perfect for Kids, Beginners, and Artists! by Megan Johnson

This is my first experience with polymer clay but I found that it doesn't harden in the oven. I followed the directions and baked at 275 degrees F for a while depending on the thickness of the item, but after it was done and cooled it was still flexible which wasn't what I wanted. I ended up baking it longer to get it. a little firmer, but you can still press it in with your fingernail.