This was a super fun project that would be completely "worry-free" with older children. I did it with preschoolers, age 2 1/2 to 5!!!
Because of their ages, we had a nice all-ears-and-eyes-on-me talk before we began! I explained that the rocks were HOT and that they were not to touch them with anything but the crayon. I showed them how I had to pick each rock up with big oven mitts. I demonstrated how to hold their crayon up and away from their hand. I showed them how to hold the edge of the plate to turn or steady their rock. I went back and asked, "What are you not supposed to touch?" Cute... they unanimously yelled, "The ROCK!!!" I asked, "What can you touch?" "The Plate!!!!"
Please note: the rocks are not hot enough to cause any real harm if touched, but it would smart.
When I was confident that everyone knew the rules, I started with getting one rock from the crock pot and let one child begin. All the others watched with fascination, paying close attention, and anticipation of their turn. Gradually, every child had a hot rock and they loved it! (I had an adult helper for every two or three kids) We did great. No owies!
My teenage helpers were completely enthralled with it too!
Getting the rocks hot!!!
The kids at work!