How to Make an Invisible Ink Message

Do you want to write your password down so that no one can see it, or do you want to send someone a secret message? Knowing how to make an invisible ink message will have you feeling like a secret agent in no time.

Method 1

Method 1 of 5:

Lemon Juice Invisible Ink

1
Squeeze the juice of half of a lemon into a bowl.^{[1]
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2
Add a few drops of water. Stir the juice and water with a spoon.

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3
Dip a cotton swab into the lemon juice mixture and write a message on a piece of white paper.^{[2]
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Research source} A feather, a toothpick, a fountain pen, a paintbrush or a calligraphy pen will also work in place of the cotton swab.
4
Allow the invisible ink to dry. As the ink dries, your message will disappear.^{[3]
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5
Hold the paper that contains your invisible ink message over a light bulb or flame/candle. Keep the paper near the bulb or flame/candle until the message reappears. Be careful not to put the paper too close if you are using a flame/candle.^{[4]
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Method 2

Method 2 of 5:

Baking Soda Invisible Ink

1
Dip a cotton swab into a mixture of 1/4 cup (60 ml) of baking soda and 1/4 cup (60 ml) of water. Use the swab to write a message on a white piece of paper.^{[5]
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2
Wait until the ink is dry.
3
Dip a paintbrush into some grape juice concentrate or any dark juice. Paint the grape juice over your message and wait for the message to appear.^{[6]
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Method 3

Method 3 of 5:

Milk Invisible Ink

1
Dip a cotton swab into a shallow dish of milk.
2
Use the cotton swab to write a message onto a white piece of paper. Allow the milk to dry.
3
Dry the message for about 30 minutes.
4
Expose the message to heat. You can use a light bulb, candle/flame, or an iron. The milk will heat up at a slower rate than the paper, which will cause the message to reappear.^{[7]
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Method 4

Method 4 of 5:

White Crayon Invisible Message

1
Use a white crayon to write a message onto a white piece of paper.
2
Paint over the message using watercolors and a brush. The message will reappear.^{[8]
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Method 5

Method 5 of 5:

No Ink Invisible Message

This method relies on pressure and indentation of the paper.

1
Lay out two sheets of paper. Place the first sheet of paper under the second piece.
2
Write your message on the top paper. Do this by applying strong pressure on the pen or pencil.
3
Remove the first sheet.
4
With a pencil, gently shade over the bottom sheet. The message will appear, similar to chalk on a blackboard.

Community Q&A

Question

Are there other ways to make invisible ink?

Community Answer

One other way is to take the highlighting part out of a fluorescent yellow highlighter and leave it in warm water until most of the highlighter is out. Then you can dip a Q-tip in the highlighter water and write a message. Once it dries, turn off the lights, or go into a dark area and take a UV light or blacklight and shine it onto the message. The message will be revealed!
Question

Will a light bulb work, or does it have to be heat?

Community Answer

As long as the light bulb isn't LED, it should generate enough heat to display the message; just be sure not to hold it so close that the paper catches fire.
Question

Could I use a hair dryer as a source of heat?

Community Answer

Yes, but it needs to be on high, and don't hold it too close to the paper or it could catch fire.