I took the basic idea of sidewalk chalk paint (2 Tbsp. corn starch, 4 Tbsp. water, drops of food coloring) and froze it in cubes. Then we took them outside to let them melt all over some big pieces of paper. The moment we got everything set up, the clouds covered the sun. It was still hot enough to melt the ice cubes, but it took a little longer. I started them with spoons because I hate things staining my hands, but my youngest quickly abandoned hers for her hands. Which it's supposed to be a sensory experience, so she figured out the right way to do it despite her mother's phobias.
This activity could be done, and might be more fun, straight on the sidewalk. I used paper because we have a brick patio and it would be hard to slide the ice cubes around on it. The girls had fun, but again, it's potentially messy. I picked it because it sounded fun and I know I need to stretch myself to allow messy play to happen.
I also made Kool Aid playdough, which has been a huge hit. It smells better and the color was better than when I've used food coloring.
In a pot, combine:
1 c. flour
1 c. water
1/4 c. salt
2 tsp. cream of tartar
1 Tbsp. baby oil (you can use vegetable oil, but baby oil makes it smoother and smells better)
1 packet Kool Aid
Stir constantly over medium heat until a ball forms. Remove from pot and let cool. Knead it a few times to get it smooth.