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For best results, use sidewalk chalk instead of chalkboard chalk. It is much more pigmented. The more chalk you use, the more paint you will have. Use two different colors to create a new color! Place the bag with the chalk inside of it on top of a hard surface, such as a wooden board or a sidewalk. Hit the chalk with a hammer several times until it turns fine and powdery.  Take this time to create more colors. Use one color of chalk per bag. If you are using a thin bag, such as a sandwich bag, place a paper towel under it, and another one on top of it. This will keep the bag from ripping. Make sure that the jar is big enough to hold at least 1 cup (240 milliliters) of water. If you smashed multiple bags of chalk to create more colors, use a separate jar for each color. Use If you one piece of chalk, use ½ (120 milliliters) of water. If you used two pieces of chalk, use 1 cup (240 milliliters) of water. Stir the paint well until the chalk dissolves. If you need to close the jar tightly and shake it to help mix the water and chalk.  If you smashed additional bags of chalk, you will need another ½ to 1 cup (120 to 240 milliliters) of water for each batch. You can thicken the paint by adding 1 tablespoon (15 milliliters) of white glue to it. Keep in mind that this will make the paint permanent. Apply the paint using a paintbrush. When you are done using the paint, close the jar tightly. If the paint starts to turn too thick, add some water to it to thin it out again. You should be able to dilute it 5 to 10 times before it becomes too thin to use.  The chalk may settle in the water. If that happens, stir it back up again. If you added glue to the chalk, use it on paper—unless you want it to be permanent!

Summary:
Place 1 to 2 pieces of colored chalk inside a resealable plastic bag. Smash the chalk into a powder with a hammer. Pour the powder into a jar. Stir in ½ to 1 cup (120 to 240 milliliters) water into the powdered chalk. Use the paint on a sidewalk or driveway.