After reminding everyone, how frugal sidewalk chalk activities can be, I decided to share the chalk recipe that we used. It was much easier and cheaper, than many I have seen.
Here is the recipe that we found to be, not only the easiest to use, but the most inexpensive that produced the desired result.
Begin by making sure you have a mold or molds of some kind. Candy molds, soap molds and even muffin pans work great. You will need to purchase a bag of plaster and some tempera paint, either liquid or powdered, which can often by found at discount department store chains, in the craft aisle, but is more commonly found at craft stores. One bag of plaster made well over 100 pieces of chalk for us. We also tried out different variations of plaster, and found that they all work about the same, so if you find a cheaper kind, go for it.
In a plastic bowl, you will need to mix one cup of the plaster to one cup of the water. If you want to make more, just double, triple or quadruple the recipe. This will make a basic, white chalk. But of course what child wants just white, right? So in order to make colored chalk, you will need to add some Tempera paint. If you are wanting to work with several colors, I suggest mixing one cup of plaster and one cup of water, for each color you want.
Add some Tempera paint and mix it into the plaster mixture. Just keep adding until you get the color you are looking for. When you have completely mixed the color in, you can begin pouring the plaster into your chosen molds. Provided that you used smaller molds, the drying time should be approximately 4-5 hours. If you chose a toilet paper tube, or paper towel tube, cover the end with waxed paper and a rubber band and pour the mixture inside. The drying time for these, is typically a few days. If the chalk doesn’t seem completely dry when you remove it from the molds, allow it to air dry for several hours to one day. Repeat for each color you would like. Enjoy!