Color Changing Invisible Ink (Using Leftover Hand Sanitizer)


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Since having kids, I have fallen in love with all things related to treasure hunts, secret messages, and invisible ink. I love that I can make a little fantasy world of mystery with my kiddos. So when I learn about a new way to add some mystery to their lives, I can’t wait to share it. 

This time, I’ve figured out how to make color changing invisible ink with things I have lying around the house. No special pens or lights, and no heat involved. Just some turmeric, baking soda, and hand sanitizer (I had a giant bottle just sitting around after a certain pandemic).   

To make color changing invisible ink, mix water and baking soda and brush a secret message on a piece of paper. To reveal the message, mix turmeric with hand sanitizer (or rubbing alcohol) and paint the solution over the paper. The paper will turn yellow, but the secret message will turn red. 

Related: How to Weather Paper to Make it Look Old (The Ultimate Guide)

This article is originally from www.dadstuffsite.com

Supplies:

  • ½ cup water
  • 1 tbsp baking soda (sodium bicarbonate)
  • ¼ cup rubbing alcohol or hand sanitizer (not the thick kind. The one that is super runny)
  • ½ tsp turmeric
  • Paper (watercolor paper is best)

Directions:

1. Make the Invisible Ink

To make the invisible ink, mix the water and baking soda. Use warm water to help the baking soda to dissolve. If it’s not completely dissolved, that’s fine. You may need to occasionally stir the mixture if everything has settled. 

Baking Soda and warm water
Stir the baking soda in the water

2. Write a Secret Message

Use a fine tipped paint brush, dip it in the baking soda/water mixture and write out your secret message. 

Baking soda and water mixture brushed onto plain paper to read the message "Ben Stinks"
Invisible ink message written on plain paper

This article is originally from www.dadstuffsite.com

A Note About Paper Selection

I found that thicker watercolor paper works the best. You can send and reveal secret messages with regular paper, but because you’re writing with water, the paper tends to get a little wrinkly. Also, if you look at the paper at the right angle, sometimes you can see a difference in sheen revealing your secret message. This is made even more obvious with smooth and glossy paper (even if it’s just a little glossy).

What good is a secret message if you can see just see it in the light or on wrinkled paper?

This is the major advantage to using watercolor paper. The paper is thicker, so it won’t wrinkle (unless you get the paper super saturated), it’s textured, and it has a flat finish. Combined, it hides the message much better than plain paper. 

Baking soda and water mixture brushed onto watercolor paper to read the message "Sam Smells"
Invisible ink message written on watercolor paper

Looking for another art activity? Check out DIY Dragon Eggs (For Rainy Days, Parties, and Just Because).

3. Reveal Your Secret Message

To reveal your secret message, we need to first mix a solution. Mix the hand sanitizer (or rubbing alcohol) and turmeric in a bowl. Just like the baking soda, the turmeric doesn’t love to dissolve, so you may need to occasionally mix up the solution. 

Photo of turmeric being mixed into a bowl of hand sanitizer
Mix ½ tsp turmeric to ¼ cup rubbing alcohol or hand sanitizer

This article is originally from www.dadstuffsite.com

Dip a foam brush (or a small rag or crumpled paper towel), into the turmeric solution and brush it across the paper. You don’t need a lot of the solution to reveal the message, so don’t saturation the paper; it’ll just create a mess. 

Brushing turmeric/hand sanitizer solution over a secret message to reveal "Sam Smells" in red
Brush the turmeric/hand sanitizer solution to reveal the secret message

Related: Dripping Melted Crayon Art (Easy Project for Kids)

A Note About Hand Sanitizer

A quick note about the hand sanitizer. At the beginning of the pandemic, there was a major shortage of hand sanitizer. Some alcohol distillers used their booze-making equipment for producing larger bottles of hand sanitizer. 

Image of a bottle of hand sanitizer
Bottle of hand sanitizer

The difference is that they often didn’t add thickeners, so the hand sanitizer stayed runny. This is the stuff you want to use. You can use the thick stuff; it’ll just leave a thicker mess on the paper. An alternative is to use rubbing alcohol (or if you have some lying around, some Everclear). 

Dad tip: Turmeric will stain your clothes and table. (I learned this the hard way). When decoding your message, place the paper in a baking sheet. And be sure to wear a shirt you’re not in love with. 

Why does the secret message turn red?

The reason baking soda turns red when mixed with turmeric is because turmeric contains a chemical called curcumin. When curcumin is mixed with an acid it turns yellow, but when mixed with a base, it turns red. 

Baking soda is a base, so adding a turmeric solution turns the message red. Baking soda is also white, so a solution of water and baking soda will dry white on paper making it look invisible. 

To learn more about secret codes, check out 6 Secret Codes and Ciphers to Teach Young Kids.

This article is originally from www.dadstuffsite.com

Can you use something other than baking soda?

If you don’t feel like messing around with mixing baking soda and water, use a little laundry detergent. If it’s too thick, water it down a little (or if you’re lazy, just use it straight from the cap). 

The cool thing is you can use just about anything as a substitute to baking soda as long as it’s a base. The problem you come into is that other than baking soda and laundry detergent, most household items that are basic are drain cleaner, bleach, and ammonia. And for the record, I DO NOT recommend using those items (just to be clear). 

Gregory Grabowski

Greg Grabowski is the principal creator of DadStuffSite.com, a website for dads by dads. Inspired by his two boys Ben and Sam and his wife Dianna, Greg loves to make things, learn things, and loves doing fun stuff with his family.

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