I created a Halloween Escape Room for my kids that has a secret message that must be revealed. Earlier this week, I showed you how to create a hollowed-out book for the escape room as well. This time I’m going to show you how to send an invisible message on paper.
One of our favorites is creating secret messages on paper. It’s a great way to teach science to kids to show them the difference in a physical change and a chemical change.
Table of Contents
Physical vs. Chemical Change
When you have a physical change, the matter is just changed in appearance, but not composition. For example water changes into ice. You can still get back to the original water.
When you have a chemical change, you create a new substance and cannot get back to the original substance.
What do you need to create an invisible message on paper?
There’s a few ways to do this. My favorites are made with things you have at home.
You’ll need white copy paper and cotton swabs as well as water, watercolors, a white crayon, blackberries, lemon juice, milk, and baking soda.
Invisible Message #1
This is my favorite way because it involves blackberries, which I love.
You’ll mix 2 tablespoons of baking soda with 1 cup of water. It doesn’t matter if the baking soda is completely dissolved.
Take a cotton swab and dip it in the baking soda water and gently tap off the excess. Then, write a message with the cotton swab on the paper. You’ll need to keep dipping the cotton swab as you write the message.
Allow the paper to dry, which can take up to an hour if you write a lot. Or, you can use a hair dryer to speed up the process.
Then, take a blackberry and rub over the entire paper to see the message. It will darken in color to a dark purple color. You could also do this with a paint brush and grape juice.
Invisible Message #2
Take just a couple of tablespoons of milk in a small bowl.
Then, write a secret message on a new piece of copy paper using a cotton swab.
Allow the paper to dry, which can take up to an hour if you write a lot. Don’t use a hair dryer on this one as milk reacts to heat.
Next, this will take a grownup. You can reveal the message in a few different ways. We tried a candle and a an electric burner on the stove. Both worked to heat the messages up to turn brown. Just hold the paper away from either the candle or stove so it doesn’t catch on fire, but heats it up. You can also use an iron hot iron or holding the paper in front of a 100-watt lightbulb — not an LED lightbulb.
As you heat up the paper, the milk will burn and turn brown revealing the secret message.
Invisible Message #3
Take just 1-2 tablespoons of lemon juice in a small bowl.
Then, write a secret message on a new piece of copy paper using a cotton swab.
Allow the paper to dry, which can take up to an hour if you write a lot. Don’t use a hair dryer on this one as like milk, lemon juice also reacts to heat.
We found lemonade works just as good and lime juice is very light. We were out of lemons, so I gave my daughter some fresh lemonade (not made from concentrate) to use instead.
Next, this will take a grownup. You can reveal the message in a few different ways. We tried a candle and a an electric burner on the stove. Both worked to heat the messages up to turn brown. Just hold the paper away from either the candle or stove so it doesn’t catch on fire, but heats it up. You can also use an iron hot iron or holding the paper in front of a 100-watt lightbulb — not an LED lightbulb.
As you heat up the paper, the lemon juice (or lemonade or lime juice) will burn and turn brown revealing the secret message.
Invisible Message #4
Write a secret message on a new piece of white copy paper using the white crayon.
This one doesn’t need to dry! You’ll need to get some watercolors and brush a dark watercolor over the message to reveal it. The watercolor reveal was very surprising to my daughter.
One thing that did not work was scribbling over the crayon with a darker crayon.
Which invisible message is just a physical change?
Of the invisible messages shared with you, which ones are chemical changes and which ones are physical changes?
Did you guess there was only one physical change? It’s the crayon one. There is no chemical reaction happening. It’s just watercolor darkening the paper around the white crayon.
The rest of the invisible message methods are chemical changes because they are reacting with the thing that is revealing the message such as heat or the blackberry.
Will you send an Invisible Message on Paper to someone?
In our Halloween escape room for tweens and teens, there is a hidden secrete message somewhere that once found must be revealed with one of these methods. You can get this free printable here! (COMING SOON)
More Fun Kids Activities
- Tooth Decay Experiment
- Make a Kite from a Garbage Bag
- Pool Noodle Poppers
- Marshmallow Catapult
- Paper Cup Puppets
- Water Bottle Fun