Using cranberries and baking soda, you can create invisible messages that will be revealed to friendly eyes and self-destruct before your enemies have a chance to read them. You’ll see how some pigments in fruit can change color when they’re exposed to an acid or a base.
I showed viewers how to make Spy Juice on Kare11 this morning. Here’s the link, if you want to watch a video demonstration!
You will need half a bag of cranberries, water, baking soda and some printer paper. To write your message, you’ll also want to find a small paintbrush, Q-tip, or something else with an absorbent tip. We made our own pens by wrapping a tiny piece of paper towel around the pointed end of a wooden skewer and winding scotch tape around to secure it. Be sure to put on an apron or wear old clothes for this experiment, since cranberry juice stains!
Have an adult or teenager boil the cranberries in about three cups of water for 15 or 20 minutes. Be sure to put a lid on the pan, since the small pockets of air that help cranberries float can make them explode as they cook. If you listen, you’ll hear some of the them popping! Crush the cooked berries and push the liquid through a sieve or colander to collect the concentrated cranberry juice. Most cranberry juice from the grocery store is diluted with water, corn syrup and other juices and won’t work as well!
Let the juice cool and pour it into a casserole dish or cake pan that the paper you’re writing your messages on will fit into. If your cranberry juice seems thick and syrupy, add a little water (maybe half a cup.) It has to have enough water in it so that it will soak into the paper!
Add a few teaspoons of baking soda to about 1/3 cup of warm water and dissolve it as well as you can. (Don’t worry if you can still see some baking soda.) Using a Q-tip, paintbrush, or your homemade writing tool, use the baking soda solution to write a message on your paper. It may take a little practice, so don’t get frustrated. You’ll get the hang of it!
Let your message air dry, or speed things up with a blow dryer.
To reveal your message, place your paper in the cranberry juice and see what happens!
The science behind the fun:
Cranberries contain pigments called anthocyanins (an-tho-SY-a-nins), which give them their bright color. In nature, these pigments attract birds and other animals to fruit. This is important because animals eat the berries and spread plants seeds from one place to another.
These pigments, called flavanoids, change color when they come in contact with acids and bases. Cranberry juice is very acidic, and the pigment is red in acids. When you add it to a base, it turns purple or blue. Baking soda is a base, so your baking soda message will turn blue when it comes into contact with the pigments in the cranberry juice. Eventually, when enough cranberry juice soaks into the paper, it will dilute the baking soda and make the paper acidic, turning the pigment back to red and your message will disappear!
There are over 300 kinds of anthocyanins which are found in many fruits and vegetables including blueberries, red cabbage, grapes and blueberries. Scientists think they may have many health benefits and some researchers are even making organic solar cells using flavanoids!
What other juices can you use to reveal secret messages? What other bases could you use as ink?
Try making your own recipe for spy juice! I’d love to hear how red cabbage works! Check out my red cabbage litmus paper experiment to find out how to make red cabbage juice.
Let me know what works best!
My kids love to play spy games. They spy on us, they spy on each other. They write notes in code and hide them all over the house. I knew right away that they would have fun with this science project. There’s definately enough 9-year old girl left in me to think it’s really cool too! This is a project that kids can actually do IN their science notebooks (or, they can just tape their note into the notebook when it is dry.) Like most projects, it doesn’t work perfectly. However, it is fun and you will see a message appear although it may be fuzzy.
All you need is paper, water, baking soda and grape juice. Simply add a few big spoonfuls of baking soda to a cup of water and mix it well (I heated the solution in the microwave to warm it in an attempt to dissolve more of the soda.) Dip a paint brush in the mixture and write a message or draw a picture on your paper. Let the paper dry completely.
When you are ready to reveal the secret code, have them paint over the paper with grape juice. Don’t use to much, or it will be a sloppy mess. The grape juice will react with the baking soda on the paper,changing the acidity of the grape juice and causing the words to appear a little darker than the background of the regular juice. Ours turned green. You could also try some different types of juice to see what happens. Have your kids record their results in their science notebooks! If they are interested, have them look up the definition for acid and base on a science website like chemistry.about.com.
The words weren’t very clear, but it was still a fun project and my kids loved it. Maybe your kids can perfect the technique. After all, trouble-shooting is a great life skill.