I have had these in my head to do for awhile now and we finally made them. We used 3 bars of Ivory Soap to make 4 bath crayons, but we made them rather large. We grated the bars with a cheese grater then slowly added spoonfuls of warm water to the grating until it begins to stick together and you can form it. We divided the mixture into four containers and added food coloring. This was the fun part. We squished and mushed the mixture up in our hands. *WARNING* Your hands will get colored....but it washes off, so no worries. We formed them into fat crayon shapes. We let them dry for almost a week. I suggest putting them up and out of sight. My two were asking me every 20 minutes if they were ready yet, so I put them on top of the fridge until they were completely dry. Then when I brought them out for tub time, they were super excited.