Homemade Invisible Ink Experiment

Have you ever visited Rachelle Doorley’s site Tinkerlab?  It’s devoted to encouraging creative thinking in kids (and adults too)!  I’ve been a fan of Rachelle’s for a while, so I was incredibly excited to hear about her recent book release.  It inspired Engineer, Snoopy, and I to delve into our very own homemade invisible ink experiment!

Amazon links below for your convenience.

Just so you know, I received a free copy of TinkerLab: A Hands-On Guide for Little Innovators.  As always, my thoughts and ramblings are 100% mine.

The Book

When our copy of the book arrived, Engineer and I opened it right up!  We sat together, leafing through page after page of inspiring activities.  He and I have a long list of ideas to try out in the near future.  I loved the bright photos and clear directions, along with the sense of encouragement and excitement Rachelle infuses into every page.  Engineer loved the huge amount of fun and creative ideas!  My son is, inherently, a tinkerer — he likes to know how and why things work; he enjoys taking things apart and rebuilding them; and he is just plain curious!  So the Tinkerlab book is perfect for him (and me)!

The book is broken up into 7 headings – Creating Your Tinkerlab, Tools for Tinkering, Ten Tinkerlab Habits of Mind, Design, Build, Concoct, and Discover. There are a total of 55 experiments in the book, each with its own supply list, directions, and ideas for experimenting further.

The Homemade Invisible Ink Experiment

We decided to try making our own homemade invisible ink first.  Engineer’s friend Snoopy was interested in trying it out with us, which made it even more fun!

First, we gathered our materials:

• White construction paper
• Precision tip Q-Tips
• Lemon
• Lime
• Cow milk
• Almond milk

We squeezed lemon juice into one container, lime juice into another, then poured the different milks into their own cups.  The cups were all set out on the kitchen table, along with Q-Tips and construction paper.

Then I helped the boys fold pieces of construction paper into fourths.  Each box was labeled for a different invisible ink ingredient – lemon, lime, cow milk, and almond milk.  As we were labeling our papers, we talked a bit about how invisible ink was used in the past.  The boys and I predicted which liquids would work well, and we also wondered if the kind of paper we used would affect our experiment.

Together, we took turns painting and writing with the liquids and the Q-tips.  Once we were all done, we set everything aside to dry for the rest of the day.

Coming back the next day, we grabbed an iron and our papers.  After letting the iron heat up, we carefully applied it to our papers.  The boys and I were fascinated as some of our writings and drawings began to darken!  Based on our experiment, we determined that the citrus juices worked very well, as did the cow milk.  Our almond milk didn’t do much at all, though!  Citrus juices and cow milk are both acidic, while almond milk is not.  The acid broke down the paper a bit, making our homemade invisible ink burn faster than the paper when exposed to the iron.

Alternatives to Homemade Invisible Ink

The boys and I tried a few other methods of creating secret messages for each other.  We tried out glue resist painting, and the oldie-but-goodie white crayon/pastel on white paper.  They really got into drawing and writing notes to each other with white crayons, then switching papers and using watercolors to discover the “hidden messages”.

Have you and the kiddos ever made your own homemade invisible ink?  If so, how’d the ink turn out?  Any other suggestions for writing secret messages?

Coffee Cups and Crayons was also inspired to try out invisible ink – be sure to see how her experiment turned out!