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Image retrieved from https://giphy.com
This lesson is inspired by Jeronicus Jangle’s paranoia when meeting Journey for the first time. Jeronicus asked Journey to sign a contract with a special pen. When Journey goes to sign the contract, no ink appears on the paper. It’s not till Jeronicus moves the paper under a special light when the ink finally reveals itself and shows Journey’s signature.
Students will create hidden messages and patterns using thermochromic ink. A simple yet fun project for every age group and like Jeronicus, we will place our own unique mark on our work and inventions.
Thermochromic inks, dyes, pigments are temperature sensitive compounds, developed in the 1970s, that temporarily change color with exposure to heat. They come in two forms, liquid crystals and leuco dyes. Most thermochromic materials are based on liquid crystal technology. At specific temperatures the liquid crystals re-orientate to produce an apparent change of colour. The liquid crystal material itself is microencapsulated - i.e., contained within microscopic spherical capsules typically just 10 microns in diameter. Thermochromic pigment changes to a clear powder when heated to 77-88 degrees Fahrenheit. The process is also reversible: when it gets cold, the pigment returns to its original color.
(image shows how the thermochromic paint reacts when a hand is pressed on its surface. The pain reacts to the body heat and turns transparent, leaving a imprint of the hand)
Begin by gathering the necessary material and tools for the lesson.
This is the step where you think of your special message that you want to hide from unwanted eyes. This message can be anything, a famous quote from someone who inspires you, a combination to a safe with your most treasured items or just something simply fun. Think about it and write it down on the paper using either a marker or pen.
Now for the key moment: Mix spoonfuls of thermochromic pigment into binder (glue, mod podge, slikscreen base), following a 1-to-2 ratio of pigment to binder. Use a wooden skewer to stir until fully combined and clumps are dissolved. *In order to hide our secret message, we want to cover it with an image on top. Since we want the thermochromic pigment to fade clear, it is recommended to use a clear binder (glue, mod podge, silkscreen base, etc). Make sure to not add any inks or paint if you want our image to fade clear.
With your paint brush, dip the tip into the thermochromic pigment mix and begin to paint your image. For this project I used a stencil of a Christmas tree that I made in the lab. Its not necessary for you to use a stencil. A simple shape like a square over your message will be more than enough.
Tada! After your image dries you can test out your hidden message. Either use your body heat by pressing your hand over the image or use an external heat source (be cautious and ask for help when using external heat source.)
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