Inside: Experiment with acid and alkaline compounds to obtain natural colors from red cabbage and use them to paint a world under the ocean. Add a pop-up shark and treasure chest for an extra bit of creativity and to get in the mood for shark week. It’s a shark art and color science experiment all in one activity.
Do you like to throw around ideas to get your kids’ creative juices flowing? I do, too! Some time ago, looking at my kids playing with maple leaves in our backyard, I began to wonder if we could extract the color out of those leaves and paint with it (Maple Leaf Science).
We tried it with my kids, and it was a wild success.
It got my kids wondering what other leaves we can try and what other colors we can obtain naturally.
After a bit of experimenting, we discovered that red cabbage leaves give us a variety of colors from pink and purple to blue and green. We used these colors to paint pictures and eggs, as well as to color bath water, lemonade, ice cream, and daisies.
Today I want to show you what we did to extract colors, but that’s not all. My kids remembered that shark week is coming up next month (it’s a week-long celebration of everything shark on Discovery Channel), and wanted to add a pop-up shark and a treasure chest to our beautiful underwater scenery.
If you are in the mood for some science experiment + shark art, follow along.
What you need
A head of red cabbage
¼ tsp baking soda
¼ tsp lemon juice (or vinegar)
3-4 jars, yogurt containers, or cups
Print out a shark silhouette or draw a shark
Underwater stickers (optional)
Sticks and tape (for optional cover)
What to do
- Chop red cabbage, cover with water, and simmer for 30 minutes.
- Pour the contents of the pot through the colander to strain out the cabbage. If you want a more concentrated and vibrant color, put the liquid back into the pot and boil it down to half the volume.
- Divide the cabbage juice between cups.
- Add baking soda to the first two cups.
Start with a tiny amount of baking soda (¼ teaspoon) and add more as you go. A bit of baking soda turns the juice a blue color. More baking soda turns the cabbage juice green. Once it turns green, it might be impossible to go back to blue.
- I took the cups outside for better lighting. We used one teaspoon of soda in the left cup (green color). And less than ¼ teaspoon of soda in the middle cup (blue color).
We added lemon juice to the third cup and got a pink color. The fourth cup (not on a pic) is an original cabbage juice left as a control sample (naturally purple).
Did you also end up with blue, green, punk, and purple colors obtained from one cabbage head?
- Now dip a brush in your all-natural paints and saturate the paper. Even our toddler had fun doing it. Paint at least two pages for each piece of art and let it dry overnight.
- Fold the piece of paper in half horizontally and cut a pair of slits across the equator of the card like on the pic below.
- If you are adding a treasure chest, cut two more lines. We googled “pirates treasure chest” and found just the thing we had in mind.
- Google “shark silhouettes,” print (or draw one yourself), and cut it out. We decided to draw a shark we found by googling “shark picture for kids.”
- Everyone ended up with a different shark. My daughter traced the shark I drew on white printer paper and colored it with pencils.
- Glue the shark and the treasure chest to the spaces between the slits.
Try closing and opening the card before you apply the glue to make sure everything fits the way you want it to. You might need to extend the slits, depending on the height of your shark and treasure chest.
- Add bubbles if you want. My kids really wanted the bubbles, so we drew circles on a piece of paper, and then colored, cut, and glued them.
If you have done everything according to our instructions so far, you will have ended up with a card that looks like this on the outside.
- Don’t worry! We are going to take the second piece of painted paper and glue over it to over to cover the cuts and slits. Keep the painted side on the outside.
Do you see the double layer of paper? You can do a better job than us of squeezing the two pieces of paper together while the glue is drying.
My daughter decided to add some puffy fish stickers for extra fun.
You can also use the outside side to write a message. We spent a few days thinking about our message and picked, “I love sharks.”
We used sticks to write the text. My kids made the message with sticks first and were then planning to glue it down piece by piece. But I mentioned that they could also tape it down and they liked that idea.
Voila! By opening and closing the card, your shark looks like it’s moving. Isn’t it cute?
The Science Behind Red Cabbage
Your kids will probably ask what happened to the cabbage juice and why. Here is an explanation in a nutshell.
Red cabbage leaves contain color molecules called anthocyanins. They’re water-soluble, which means that when you cook cabbage leaves, they dissolve in water. That’s why we discard the leaves and keep the water we boiled the leaves in.
Red cabbage juice changes color depending on what it’s exposed to. On its own, cabbage juice is neutral and purple in color. When you add an alkaline compound (or base) like baking soda, it turns blue. As you keep adding even more baking soda, it’ll start turning green.
On the other hand, when you create an acidic environment by adding vinegar or lemon juice to red cabbage juice, it turns pink (or reddish). (What’s interesting is that when you leave it out all night, it goes back to purple in the morning. I’m not sure if it’s because the acetic acid (vinegar) decomposes over time or because vinegar absorbs moisture from the air and it lowers the acidity in the cup.
Anthocyanins are fascinating, and we can’t get enough of experimenting with them. Next time we will show you how we use blackberries to make ink for writing on homemade parchment paper (aka Egyptian research).
Let us know if you liked our shark art and if you’re planning on watching Shark Week this year.
Looking for more Under the Sea Craft ideas?