I want to make impressions of dd's footprints that can be put outside in the garden as a gift for my mom. The research I've done says to use cement, I don't want to stick her little parts in cement. All the air dry clay I've seen isn't durable enough for outdoor use. When I was a kid I had some clay that we baked in the oven, the ashtray I made has been on my mom's deck for 20 years (they don't smoke, not sure why I thought they needed an ashtray) but I have no idea what the product was. I could arrange use of a kiln but it's mom's kiln so that would ruin the surprise. Any material suggestions? Thanks.