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Throwing Away the Plan: Doing Fun Science at Home during School Closures (Activity #8)

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By Sandra Slutz on April 3, 2020 11:00 AM

Follow along with a Science Buddies parent who is using family STEM activities to keep her kids learning at home during the COVID-19 school shutdown. New posts every Monday, Wednesday, and Friday. Today's adventure... writing secret messages with invisible ink.

Student hand with multiple examples of messages written with invisible ink that has then been revealed using either an iron or turmeric in this science activity

Oops... New Plan Needed!

How many plans have you made since your school closed? Are you on your first or fourth family schedule? Have you tossed all schedules out the window? We've made a lot of plans and thrown a bunch of them away. Today was a "throw away the plan" day. I had planned to do the Walking Water activity, which is really cool and very pretty, but somehow the day got away from me. By the time we were ready to start our science time, it was already late afternoon, and there was no way Walking Water was going to fit in the day. So, I did what we're all doing these days — I winged it.

I went to the Science Buddies list of STEM activities and simply started browsing through looking for something that fit my criteria: 1) materials I had at home, 2) could be done in an afternoon or less, and 3) would interest my second grader. Here are a few options that made my short list:

Secret Messages With Invisible Ink!: every kid likes to feel like a secret agent.
Can You Catch a Bubble?: the materials are simple, and the challenge itself is fun.
Build a Gumdrop Geodesic Dome: grapes and strawberries can easily be substituted in this cool building activity.
Curl Metals With Heat!: the behavior of simple aluminum foil and paper in this activity is unexpected and fascinating.
Do-Re-Mi with Straws: all it takes to make music is a straw and a pair of scissors.

My Pick of the Day: Invisible Ink

I didn't actually pick today's activity; my second grader did. When presented with the five options above, she was pretty quick to choose the Secret Messages With Invisible Ink! activity. The idea of making invisible ink and delivering secret messages was irresistible.

https://www.youtube.com/watch?v=AOVD7WgFP2s

Video also available en Español

This activity lays out two different methods for making and revealing invisible ink. The first method is to write with a lemon juice and water mixture and reveal the ink with heat. The second method is to write with a baking soda and water mixture and reveal the ink with turmeric, which changes color when it encounters the more basic baking soda.

My daughter wanted to try both methods, which I thought was great. Just one kink in that plan — we didn't have a lemon. We did, however, have a lime, and we reasoned that because it was a citrus fruit, it would substitute just fine.

My daughter made up both invisible inks. I was both amused and proud when she also ran over to grab some markers and an extra piece of paper to make an experiment log. Clearly the previous seven experiments have already trained her to record her observations! And yes, she spelled "experiment" wrong, but we aren't going for perfection over here. With her log handy, she started writing her secret messages and placing them into one of two zones, separated by ink type, to dry.

Writing messages with invisible ink for science activity

Student writing in informal activity log to keep track of her science experiment

After they were dry, it was time for the big reveal. We used an iron to make the lime-water ink appear. This was definitely a parental-supervision step!

Iron being applied to a piece of paper on which an invisible ink has been used

While the lime-water ink was visible after the iron, the real winner was the next method, the turmeric. That process was by far more young-kid friendly (painting on the turmeric mixture was easy), and the color that emerged was more vibrant and clearer to read.

Turmeric being painted onto a message that has been written with an invisible ink

We were having so much fun, that we went on to try a few more things, including different types of paper (discovery: card stock works better than printer paper for the lime-water ink) and other mixtures. We won't reveal all our invisible ink discoveries though — you'll have to experiment and find them out yourself!

If you discover a particularly good invisible ink recipe, I'd love to hear about it. As always, you can email me your comments and questions.

If this blog post was useful to you, please share it with other parents. Follow the links below to see what other science adventures we've been having at home.

View All Posts in this Series

A science activity log is available as a Word document or as a Google doc for online convenience. (Just choose "File/Make a copy" to save it to your Google Drive.)

About the Author

Sandra, Science Buddies' Vice President of STEM education, holds a PhD in Genetics from Stanford University and has spent the last twelve years working on science education and STEM outreach. Right now, she's stuck working from her home in the Pacific Northwest with her husband, second grader, middle schooler, and two oddly noisy gerbils. She hypothesizes her sanity will hold as long as she gets a daily dose of sunshine.

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