Rainbow Sidewalk Chalk

Make your own rainbow-colored sidewalk chalk out of Plaster of Paris. It's easy - we'll show you how!
Rainbow Sidewalk Chalk craft


  • Ice cube tray
  • Plaster of Paris powder
  • Water
  • Mixing container (paper cup or any
    disposable container)
  • Spoon
  • Poster paint
  • Petroleum jelly
  • Drinking straws (optional)

Safety Tips

  • Plaster of Paris powder should be used under adult supervision. The powder is extremely fine and easily dispersed through the air. Using a dust mask is highly recommended.
  • Never mix Plaster of Paris with your bare hands.
  • Watch out for this sign Ask for an adult's help.. It means adult help is needed for the particular step.


Step 1 Rainbow Sidewalk Chalk craft 1. Obtain an ice cube tray and grease the tray compartments with petroleum jelly.
Step 2 Rainbow Sidewalk Chalk craft 2. Choose the colors of poster paint that you want to use to make your multi-colored chalk.
Step 3 Rainbow Sidewalk Chalk craft Ask for an adult's help.3. Typically the ratio of the mixture is 2 parts Plaster of Paris powder to 1 part water. For this project you can start out with ½ cup of Plaster of Paris powder and ¼ cup of water. Mix Plaster of Paris according to the package instructions of your brand of Plaster of Paris or follow this basic mixing procedure.
Step 4 Rainbow Sidewalk Chalk craft 4. Add some poster paint once the mixture is free of lumps and has a smooth consistency. The more paint you add, the more intensely colored your chalk will be. Continue mixing from side to side until the color is uniformly dispersed.
Step 5 Rainbow Sidewalk Chalk craft 5. Pour the mixture into your ice tray mold. For a tri-colored chalk, fill each compartment a third of the way; for a two-toned chalk, fill it half of the way; and for a solid-colored chalk, fill it all the way to the brim.
Step 6 Rainbow Sidewalk Chalk craft 6. If you have a translucent ice cube tray, you can check out the level of Plaster of Paris mixture from the side.
Step 7 Rainbow Sidewalk Chalk craft 7. Level the mixture inside the tray by gently tapping the tray against the table.
Step 8 Rainbow Sidewalk Chalk craft 8. When the mixture is starting to solidify but is still soft, gently carve out shallow grooves across the surface of each block with a Popsicle stick or with the end of a spoon. The grooves will help bind the next layer of Plaster of Paris strongly with the current layer.
Step 9 Rainbow Sidewalk Chalk craft 9. Mix another batch of colored Plaster of Paris and pour it over the first layer. As with the first, carve out shallow grooves when the mixture has started to solidify.
Step 10 Rainbow Sidewalk Chalk craft 10. When the second layer has completely solidified, mix and add the final layer of colored Plaster of Paris.
Step 11 Rainbow Sidewalk Chalk craft 11. Allow your multicolored chalk to sit for at least 4 hours before removing them from the mold. Loosen them from the mold by slightly twisting the tray sideways, just as you would when removing ice from an ice tray.
Step 12 Rainbow Sidewalk Chalk craft 12. Carefully invert the tray and catch the Plaster of Paris cubes with your hand or lay them gingerly directly on the table.
Step 13 Rainbow Sidewalk Chalk craft 13. Wipe off the layer of petroleum jelly covering each cube.
Step 14 Rainbow Sidewalk Chalk craft 14. These cube-shaped Plaster of Paris chalk will be sturdier than your usual sidewalk chalk.

Now try out your rainbow-colored chalk. You can draw thick multi-colored lines with it!
Step 14b Rainbow Sidewalk Chalk craft Or make fine solid lines by drawing or writing with the chalk's corners.

More Ideas

Rainbow-colored Plaster of Paris Beads craft1 Create a hole at the center of each cube to turn them into funky big Plaster of Paris Beads that can be used for jewelry crafts or wind chime and mobile crafts. After pouring the first layer of colored mixture (Step 5), position a short piece of drinking straw (grease the straw with petroleum jelly beforehand) at the center of each cube, making sure that the straw touches the bottom of the tray.
Rainbow-colored Plaster of Paris Beads craft2 Continue following the steps in the tutorial above. After the cubes have been released from the tray, remove each straw from the Plaster of Paris cube.

Earth Friendly Tips

  • Do not throw Plaster of Paris into the drain, it will clog the pipes. If you have any leftover mixture, let it harden, then throw it into a garbage can.
  • If you want to save spoons or containers used for mixing Plaster of Paris, scrape off the hardened plaster and wipe the utensils with a damp cloth.