Learn about acid-base reaction with DIY color changing paint.
What you'll learn:
Acids and bases can change the molecular structure of a molecule.
Alterations in the structure of a molecule can lead to visible changes such as color changes.
Natural pH indicators seem like magical color changing solutions. With them we have had the chance to see acid-base chemistry in action, written secret spy letters, compared cabbage and beets as indicators, dyed Easter eggs, and learned what a pH indicator is.
In this activity we will create our own color changing paint using a natural pH indicator. As we add acids or bases to our paintings the colors will change from purple to pink, red, green, yellow, even blue!
How to make color changing paint
Chop your cabbage or beets up and boil in 3-4 cups of water for 30 minutes.
Strain, and retain, the purple liquid. Then boil this until it reduces to about 1 cup of very dark liquid.
Mix equal parts of your cabbage/beet liquid with the white powdered paint. You can add a few drops of an essential oil if you do not like the smell of the purple liquid.
Paint your first layer.
Think about the layers of art you would like to create with your natural pH indicator color changing paint.
The first layer will inevitably be purple as the paint we created is purple. Lay down your first layer of paint in your art.
Change the color of your art
You can use acids and bases to change the color of your purple paint. Experiment with adding the acids and bases while the paint is wet or dry. Do paint brushes work better than q-tips or toothpicks?
You don’t need to change the color of the entire first layer of paint – you can etch in small graphics or make wide swaths of different colors.
Color changing paint chart
Below is a chart showing the colors beet juice and red cabbage juice undergo at various pH values. You can use this to plan your art as the colors you have to paint with are varied, but you certainly don’t have an entire rainbow!
Notice how the red cabbage undergoes more variations in color with the pH changes? That is why I think using the red cabbage is a better option when making color changing paint. However, you could make both types to be able to change the paint color in different ways.
Beet (top row) and cabbage (bottom row) painted on a piece of paper at various pH values.
Note: These do now have the white powdered paint added.