Things I learned today

Today I went to a nearby elementary school to do an art project for their earth day family event. They wanted something using recycled materials, so I had an idea to make stepping stones using soda and water bottle caps as for mosaic decoration. I got my mom to help me out, which was a good thing, because I don't think I could have handled it myself.
So, here's what we did: We used pizza boxes with the tops cut off for the molds, lined with plastic grocery bags. My mom and I mixed up the concrete and poured it into the molds, and then when it was ready to go we had the kids add the decorations. Unfortunately, we had far fewer bottle caps than I had expected, so we ran out right away, and had to scrounge around for odds and ends to add to the stepping stones. It was a lot of leaves, sticks, and pine cones, which I'm hoping will leave impressions in the concrete when it dries, a lot of rocks, and some strange bits and pieces that the kids found lying around- some golf balls, pencils, even a tiny baby doll leg. So the last few stones were a little, shall we say, surreal?
Anyway- this is what I learned today:
-Pizza boxes make great stepping stone molds
-50 lbs of concrete makes about 3 12" square stepping stones.
-If you want a lot of bottle caps for a project, make sure you have a lot yourself. If other people bring more, that's a nice bonus.
-Kids are really good at finding strange things in the woods.
-As long as the kids have fun, the project was a success.