Put into bowl and grind into a powder. A mortar and pestle works fine for this. Discard any large pieces. Add food coloring if desired. Allow to dry approximately 3 days until hard.
Eggshell chalk is for sidewalks only.
If you use Elmer's School Glue instead of regular white it doesn't bounce or pick up pictures. Mix together and use. In a large bowl, mix peanut butter, corn syrup, and powdered sugar together. Add powdered milk and knead until smooth. The children can mold dough into any shape they wish.