6 Easy Ways to Write & Read Invisible Ink Messages

• Write a message with either lemon juice or milk and let it dry. Hold the paper a few inches over a lightbulb for a couple of minutes to reveal the message.
• Mix equal parts baking soda and water and write your message with a cotton swab. After it dries, spread grape juice over the paper to read your message.
• Write the message with liquid laundry detergent, and let it dry completely. Shine a black light at the paper to make your message glow.

Lemon Juice

Squeeze the juice of half of a lemon into a bowl. Cut a lemon in half with a knife, and juice half of it into a small bowl. If you don’t have a fresh lemon, use some prepackaged lemon juice instead.

Add ⁄2 tablespoon (7.4 ml) of water to the bowl. Stir the juice and water together with a spoon until they’re thoroughly combined.

Dip a cotton swab in the lemon juice and write your message on paper. Wet the end of your cotton swab and shake off the excess liquid. Use the cotton swab to leave your secret message on the paper. If the cotton swab dries out while you’re writing, just rewet it in your lemon juice. Alternatively, write your message using a toothpick, paintbrush, or calligraphy pen dipped in the lemon juice mixture instead of a cotton swab.

Allow the invisible ink to dry for 15 minutes. When the lemon juice is still wet, your message may still look slightly visible. As the invisible ink dries, anything you wrote down will disappear on the paper. To make your message even more invisible, crumple up the piece of paper so the creases hide where you wrote things down.

Heat the paper over a light bulb or candle to reveal the hidden message. Hold your piece of paper a few inches above a light bulb or lit candle for a few minutes. The heat from the bulb or flame causes a chemical reaction that darkens the lemon juice so you’re able to read the secret message clearly. Avoid holding the paper too close to an open flame since it could catch on fire. Alternatively, put your hidden message between 2 thin towels and run an iron over it on low heat. Keep moving the iron around for a few minutes until the invisible ink reveals itself. To quickly reveal your invisible ink message, set your oven to 300 °F (149 °C), and put the paper on a baking sheet. Let it heat up for 1–2 minutes until the lemon juice darkens.

Baking Soda

Mix equal parts baking soda and water in a small bowl. Make your invisible ink by combining about 3 tablespoons (44 ml) of water with 3 tablespoons (51 g) of baking soda in a small bowl with a spoon. Make sure the baking soda dissolves completely in the solution.

Write your message with a cotton swab, and let the ink dry completely. Dip the end of a cotton swab into your baking soda invisible ink and shake off the excess. Write your message on a blank piece of white paper. If your cotton swab dries out, just dip it back in the baking soda solution. When you’re finished with your secret message, leave the paper out to dry for about 15–30 minutes so the ink is invisible. If you don’t have a cotton swab, a toothpick or paintbrush will work great for writing your message.

Paint over the paper with grape juice to reveal your message. Fill a small cup or bowl with grape juice and wet the bristles of a paintbrush. Lightly spread the grape juice over the piece of paper and wait for your invisible ink message to appear. Grape juice has a natural pigment called anthocyanin, which darkens the color of the baking soda because of the change in pH. Alternatively, mix 1 teaspoon (5 g) of turmeric with ⁄2 cup (120 ml) of rubbing alcohol. Apply the solution to have your invisible ink message turn red.

Milk

Dip a cotton swab in milk and write your message on paper. Any type of dairy milk will work for making invisible ink. Wet your cotton swab and shake off the excess milk. Then, write your message on a blank sheet of white paper.

Dry the message for about 30 minutes. Leave the piece of paper in a cool, dry spot so the milk can completely dry. Once the milk dries, the message you wrote will disappear on the page.

Hold the paper over a heat source to reveal the invisible ink. Keep the piece of paper a few inches above a lit light bulb or a candle. Because milk burns at a lower temperature than the paper, your message will darken so you’re able to read it. Try putting the paper between 2 towels and running an iron on low heat over your message. Within a few minutes, the message will reveal itself. Avoid touching the paper to the candle or it could catch fire.

Laundry Detergent

Write your message using laundry detergent. Dip a paintbrush or cotton swab into liquid laundry detergent and shake off the excess. Write your secret message on a sheet of paper, rewetting the paintbrush or cotton swab whenever it dries out.

Let the detergent dry completely. Leave the paper out on a table or countertop for 15–30 minutes so the detergent has time to dry. Once the paper is dry to the touch, your message will be invisible and the page will look blank.

Use a black light to reveal the message. Point the black light at the sheet of paper and turn it on. Because detergent has whitening agents to clean your clothes, your message will glow brightly under the ultraviolet light. As soon as you turn off the black light, your invisible ink message will disappear again.

White Crayon

Write your message on a white piece of paper with a white crayon. Press down hard as you write your message so the crayon wax sticks to the paper. Avoid using any other paper colors since the crayon will be visible.

Paint over the message with watercolor paints to reveal the message. Wet a paintbrush in water and then dab a little paint onto the bristles. Spread the paint across the sheet of paper in a thin, even layer. The paint will stick to the paper but not to the white crayon wax, so your secret message will stand out from the background. Alternatively, color over the paper with a dark-colored marker. You may be able to see the message by holding the paper at a slight slant next to a bright window. That way, the wax will look a little shiny so you’re able to read it.

Pencil Indents

Stack 2 sheets of paper. Place one sheet of paper on your table or work surface. Then, set another piece of paper on top so the edges line up. This method doesn’t use any invisible ink, but instead uses indentations in the paper to reveal the message.

Write your message on the top paper. As you’re writing the message in pen or pencil, push the tip against the paper and apply pressure. It may help to go over each line 2–3 times to make sure the indentations go through to the second piece of paper.

Remove the first sheet. When you’re finished writing your message, keep the top sheet if you want to remember what your secret message says. Otherwise, just throw the paper away since the bottom copy has the message you want to send.

Shade the bottom sheet of paper to reveal the writing. Use the side of a soft pencil and gently shade the sheet of paper. The graphite will stick to the flat parts of the paper but not the indentations leftover from writing the original message, so you’ll be able to read it clearly. Avoid applying a lot of pressure with your pencil since you could make the original message disappear.