Whether you're announcing a special occasion or painting a mural, window chalk is a viable medium for decorating glass surfaces. However, window chalk can be pricey and difficult to locate, and some versions may not be the color and consistency you want for your project. Make your own window chalk to control the color and opacity of the chalk. Homemade window chalk can be made at a fraction of the cost of store-bought chalk.
Obtain a paper or plastic disposable cup for each color of window chalk you want to make. Set the cups on a flat work surface.
Crush a stick of sidewalk chalk in the color of your choice using a mortar and pestle. Mash the chalk into a thin dust.
Measure the amount of chalk dust. You need to know the amount in order to mix the window chalk.
Put the crushed chalk dust into a cup.
Add dish washing liquid to the cup. Avoid dish detergents with bleach or other additives. Use twice as much dish washing liquid as chalk.
Stir the mixture with a wooden tongue depressor until it is an even consistency. The chalk paint will be thick – about the same texture as paint made for walls. Add more detergent for a thinner or more transparent paint that allows more light in. Add less for a more opaque formula.
Repeat the process for each color of chalk you have. Use a separate cup and tongue depressor for each color to avoid unintentional color mixing. Rinse your mortar, pestle, and measuring cup between each color.