This convincing technique makes use of thickened tempera paint to evoke stained glass. After transforming your windows, the material cleans up with little more than soapy water.
For each color of paint, combine 1/4 cup cornstarch, 1/4 cup paint, and 1 teaspoon of dish detergent in a bowl and stir until the mixture is the consistency of yogurt.
Use the funnel to pour the black paint into the squeeze bottle.
Cover the floor beneath a clean glass door or window with the sheet or drop cloth. To avoid potential stains, cover any exposed wood with newspaper and painter's tape.
Use the paintbrushes to paint a picture on the window.
Once the paint is dry, use the squeeze bottle to carefully outline the shapes with black paint, creating a stained glass effect. Add more black lines as desired.
When you're ready to remove the artwork, use a plastic spatula to scrape off the paint, then wash away any remaining streaks with warm soapy water.