Summer might be over, but there are still plenty of warm days left to spend outside! Today we are going to make our own sidewalk chalk! Before we start creating, let’s learn about the science of chalk.
What do you think of when you hear the word chalk? Many of you might think of the thin white stick that you use to write on a chalkboard. Or you may have memories of colored sidewalk chalk that you play with outside. Those types of chalk are manmade, but did you know that chalk actually appears in nature? Check out the examples below!
Where does chalk occur naturally?
These chalk deposits have built up over many, many years. There are other chalk formations around the world such as the chalk cliffs in Germany and Denmark. Believe it or not, chalk is actually a rock. It’s just soft enough that you can use it to write with. Chalk is made of a substance called calcite, which is actually a form of the mineral limestone. The scientific way of denoting calcite (or calcium carbonate) is CaCO3. While blackboard chalk used to be made of this same substance, it is now usually made of gypsum, or calcium sulfate. That is what you’ll be using to make your sidewalk chalk today.
Now that you know a little bit about chalk, let’s get started!
- Toilet paper tubes
- Duct Tape
- Bucket or large mixing bowl
- Wax paper
- Tempera paint (available at Target, Amazon, and most craft stores)
- Plaster of Paris (gypsum)
- Cookie sheet
Here’s what to do!
- Collect about six toilet paper tubes. This is what you will use for your chalk mold. Cover one end of each tube with duct tape. Make sure the tape is secure so none of your chalk mixture will leak out the end.
- Measure a 6x6 inch piece of wax paper and cut it out. Roll the wax paper square up and place it inside the unsealed end of one of your cardboard tubes. The wax paper is to keep your chalk mixture from sticking to the inside of the cardboard tube.
- Repeat step 2 until you have all six of your paper tubes lined with wax paper.
- Measure out 3/4 cup of warm water and pour it into your bucket.
- Measure 1 1/2 cups of plaster of Paris and sprinkle it into the warm water. Stir as you sprinkle. The plaster will begin to harden in the next half hour, so you will want to work quickly.
- Divide the plaster of Paris mixture into six different bowls. Pick six different colors of tempera paint, and add about 3 tablespoons of paint to each bowl. Stir until the color is evenly distributed.
- Place each cardboard tube tape-side down on a cookie sheet, then pour the colored plaster of Paris mixture into each tube (one color per tube).
- Move the sheet of tubes to a place where they won’t be disturbed. It will take about three days for the chalk to dry completely. Peel the tubes and wax paper off, and voila! You have your own homemade sidewalk chalk!
Vacker, M. Homemade sidewalk chalk. PBSParents: Crafts for kids. http://www.pbs.org/parents/crafts-for-kids/homemade-sidewalk-chalk/
Chalk. Wikipedia. https://en.wikipedia.org/wiki/Chalk
Images and Video Credits, in order of appearance:
Taichi, 2005. The needles. Image uploaded from Wikimedia Commons on 8/28/2016. https://en.wikipedia.org/wiki/Chalk#/media/File:The_Needles.jpg File used in accordance with the Creative Commons Attribution-Share Alike 3.0 Unported license. No changes were made.
Yuvair, 2008. "Nitzana Chalk curves" situated at Western Negev, Israel are chalk deposits formed at the Mesozoic era's Tethys Ocean. Image uploaded from Wikimedia Commons on 8/28/2016. https://en.wikipedia.org/wiki/Chalk#/media/File:Nitzana_chalk_curves_(2),_Western_Negev,_Israel.jpg File used in accordance with the Creative Commons Attribution-Share Alike 3.0 Unported license. No changes were made.
Tribble, 2008. Child drawing with sidewalk chalk. Image uploaded from Wikimedia Commons on 8/28/2016. https://en.wikipedia.org/wiki/Chalk#/media/File:Chalk-Sidewalk-Art-0092.jpg File used in accordance with the Creative Commons Attribution-Share Alike 3.0 Unported license. No changes were made.