Magic Color Changing Raised Salt Painting: A STEM Activity

This activity takes raised salt painting to a whole new level! In this twist, we use some secret ingredients that will make the special paint change color once it hits the salt!

The above picture was made entirely by my almost four year old. And even though this was the fourth picture she had made, the process was still as magical to her as the first time.

 

The secret to the color change is in the special paint. Instead of a true watercolor, we are using red cabbage juice! Red cabbage juice contains molecules called anthocyanins that change color when exposed to different pH levels. For more of the science involved, check out this post. The painting surface, which is usually just glue and salt in the classic activity, is actually different mixes of glue, salt, and safe household acids or bases in our version. You can create the picture beforehand for your child (like I did above in the mermaid video), or they can plan and create their own science art all by themselves (like the snowman further up).

Materials

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Method

Making Red Cabbage Juice

There are several ways to get juice from a red cabbage. All of these methods make quite a bit of juice. We freeze leftover juice in an ice cube tray, then save the cubes to melt for future projects.

  • Just juice some in a juicer (if you have one).
  • Add about a quarter of the cabbage to a blender and blend with about a cup of water (adding more or less depending on how much cabbage you have). Then strain the liquid.
  • Bring ~2 cups of water with chopped red cabbage to a boil, turn off heat and let sit till it’s cool. Strain the liquid.

Making the Salt Mixes

You can safely access three colors of the red cabbage juice with household solid chemicals: blue-green, purple, and pink. Prepare the mixes in a bowls or cups. Don’t forget to label them. Make as much as you need, or save some for later. The amount you make will depend on how much glue you need to cover, but the mermaids above took about 2 tbs of each.

  1. Acidic Mix (Pink): 1 part citric acid to 6 parts table salt
  2. Alkaline Mix (Blue green): 1 part baking soda to 3 parts table salt
  3. Neutral Mix (Purple): All table salt

Making Your Art

  1. Draw your design on the paper with a pencil.
  2. Decide which parts will be blue, pink, or purple.
  3. Using the glue, trace the drawing on just the lines that will be pink.
  4. Sprinkle the Acidic Mix onto the glue (with fingers or a spoon), then shake off the excess.
  5. Using the glue, trace the parts of the drawing that will be blue-green.
  6. Sprinkle the Alkaline Mix over the new glue, then shake off the excess.
  7. Using the glue, trace the parts of the drawing that will be purple.
  8. Sprinkle the Neutral Mix over the newest glue then shake off the excess.
  9. Let dry for about 30 min (This is optional. It will still work when the glue is wet, but you just have to be careful to not smoosh it with the paintbrush otherwise acid or base crystals that get stuck to the brush may change the color of your paint stock when you double dip.)
  10. Load a brush with red cabbage juice and touch it to the salt/glue lines. Keep dabbing until your whole painting changes color before your eyes!

If you try this, be sure to share your creations with us! Find us on Instagram and Twitter @cara_florance. Use the hashtag #IBravedTheElements and we might feature you!

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