Shhh!! It's a secret!
Sending secret messages can be fun to do. Using invisible ink is a cool way to hide your messages until its time for them to be read.
There are 9 sneaky ways to make invisible ink below. You can use lemon juice, milk, baking soda, cornstarch and iodine, and a white crayon.
You will also discover how to send a message with a banana, how to make glow in the dark messages, and how to make disappearing ink.
These invisible ink recipes are great for wannabe spies and secret agents, mystery parties, pirates and treasure maps, wizards, mad scientists, or just for anytime you want to pass on a secret message.
Don't disappear, the secrets to invisible ink will be revealed below...
Other juices will work as secret ink as well. Try grape juice, apple juice, orange juice, onion juice, and even vinegar.
Invisible Ink with Lemon Juice
- Lemon juice (concentrate or freshly squeezed)
- Q-tip (or toothpick or paintbrush)
- Candle (any source of heat will work, ex. lamp, iron, oven)
The most common way to write a secret message is with lemon juice. When it dries on the paper, it will be nearly invisible. It's a great way to send messages that can't be read by everyone.
Begin by pouring a bit of the lemon juice into a bowl. If you are squeezing the juice from a lemon, you may have to add a little water.
Use a q-tip, toothpick, or a paintbrush to write your message on the paper. Don't get the lemon juice too thick or it will cause the paper to rumple where the juice is. But make sure you get enough juice on it that the message will be visible later.
Let the paper dry thoroughly. This will take about an hour.
To decode the message, you will need to heat up the paper. The best way to do this is with a candle.
Hold the paper over the candle until the words become visible. Don't let the paper actually come into contact with the flame or get too close to it. It will catch the paper on fire or scorch it. It will take awhile to fully decode the message. The words will become a brown color as they are heated up.
You can even put the paper into the oven on about 350o for about five minutes. Make sure to keep an eye on it so that it doesn't burn the paper. The oven method may be the best route if you are doing this with young children.
You can also use an iron or a lamp that is turned on, or even the sun to make the ink visible. Some of the methods will take a long time. Be careful not to get burned.
It works because the lemon juice oxidizes in the air. Heating it causes that process to speed up. The juice will turn brown on its own in time.
How to Make Invisible Ink
Invisible Ink with Milk
Milk is another thing that can be used as invisible ink. Most people keep milk in the house, so it can be easier to use than lemon juice. (It works the same way as lemon juice invisible ink if you need to peek at the more detailed instructions above).
Pour some milk into a bowl. You won't need much. Dip the q-tip or whatever you are using to write the message into the milk. Carefully write your message trying not to get the paper too wet.
Allow the milk to dry. When you are ready to read the message, just hold the paper over a candle or put it in the oven. The message will turn brown as the candle heats it up. Try to keep the paper from getting too close to the flame to avoid scorching and catching the paper on fire.
Invisible Ink with Baking Soda
- Baking soda
- Grape juice (optional)
You can make invisible ink with baking soda as well. You'll have to make the baking soda into a paste to be able to write with it.
Pour a few spoonfuls of baking soda into a bowl. Add a few spoonfuls of water. Mix it up until it the baking soda is dissolved in the water. Add more water if the mix is too dry. Add a little more baking soda if it is too runny.
Dip the q-tip into the baking soda mix and use it to write your secret message. Remember not to apply it too thick or too thin so that it will be legible without causing the paper to wrinkle. Let the paper dry.
There are actually two ways to ways to decode the message written with baking soda so it can be read.
The first way is just like the lemon juice invisible ink above. You hold the paper over the candle until the letters turn brown. Make sure you don't hold the paper too close to the flames.
The second way to read the message is to use juice. Grape juice will work best for this, but other juices will also work.
Pour a bit of juice in a cup. Dip a q-tip or a cotton ball into the juice. Rub it over the paper. As you do, the message will begin to appear.
This works because the baking soda reacts with the juice. The baking soda will even absorb the color of some juices. So if you use grape juice, the letters will turn a purple color.
Making Invisible Ink with Baking Soda
- Iodine solution
This is a type of invisible ink that doesn't need heat to be read.
First, you will need to make a paste with the cornstarch. You can just mix equal parts cornstarch and water together. But it will apply more smoothly and be less visible if you heat the cornstarch and water. This is like the method used to make gravy with cornstarch.
When the cornstarch mix is ready, use a q-tip to write the message on a piece of paper. Allow it to dry.
When it is time to reveal the message, you will need an iodine solution. Most pharmacies carry it in the health supplement section. Iodine comes in a bottle usually with a liquid dropper. It should be a about a 85-95% water solution with iodine and possibly potassium iodide.
Iodine is commonly used for first aid. There are anti-septics made with decolored iodine that will not work for this. Make sure you get an iodine and water solution.
Using a cotton ball, q-tip, or a paintbrush, rub the iodine over the paper to reveal the hidden message. The iodine will turn the message purple.
Invisible Ink with White Crayon
- White crayon
- Highlighter or marker
- Watercolors (optional)
- Paintbrush (optional)
This is the easiest method to make invisible ink and is great for younger children who want to do secret messages.
Write your secret message using the white crayon on a piece of white paper. Try to write as heavily as you can. This will make it easier to read later. The crayon writing will be invisible.
When you want to reveal the secret message, just paint over the entire paper with watercolors. You can also color over the paper with highlighters or markers if you don't want to go to the trouble of paints.
You will be able to read the secret message through the paint. Experiment with different types of markers and highlighters to see which ones make the best message decoders.
It works because the crayon leaves wax on the paper. The paint and marker won't stick to it.
Secret Message with a Banana
You can write secret messages on a banana peel that will be invisible for about an hour.
This is a fun way to send someone a message in their lunch or to pass a message without other people realizing it. Most people wouldn't suspect a banana could be a note.
Just write the message on the banana using the toothpick.
It will be nearly invisible at first. This is a good time to pass the banana to the person who is receiving the message.
After about an hour, the message will darken and will be clearly visible.
Disappearing Ink with a Pen
- Friction erasable pen (ex. FriXion made by Pilot)
- Regular ink pen
- Lighter or candle
Do you want to make disappearing ink? This is a trick many magicians use and it is my favorite way to make secret messages. The letters will disappear right from the page.
The secret is friction pens. They are erasable pens that work by friction. The brand FriXion by Pilot is a good pen to use for this. They are available at most office supply stores.
There are two ways to make disappearing messages. You can have a jumble of letters that will disappear leaving just your secret message. Or you can write a message that will completely disappear.
If you want to disguise your secret message, start by writing your secret message on a piece of paper using a regular ink pen. Leave space in-between the letters and around the words to add random letters.
Now switch to the friction pen. Write random letters around your message to disguise it.
When you are ready to reveal your secret message, hold the paper up to the flame from a lighter or a candle. A long-stemmed lighter is ideal. Be careful not to touch the paper directly to the flame or it will catch the paper on fire.
Move the paper back and forth across the flame and watch as the letters written with the friction pen disappear completely.
If you want to destroy your message after it is read, write the message using the friction pen.
Try not to press down very hard as you write or you will leave an indentation on the paper that will be visible later.
When the message has been read, hold the paper up to the lighter or candle flame. Move the flame back and forth across the paper to make your message disappear.
Now the evidence of your secret message will be erased.
Friction Pens to Create Disappearing Ink
Invisible UV Ink
Glow in the Dark Pens and Ink
- Blacklight ink or pens
Another ink that is completely invisible in normal light is blacklight ink. It glows in the dark under a blacklight.
A lot of places use this type of ink for stamping hands at the door. It is used at Chuck E. Cheese and in some clubs and bars. Many brides and other people planning parties are using blacklight pens to mark RSVP cards so they know who they came from.
You can order blacklight reacting ink or you can buy a blacklight pen. Ordering online is your best chance of finding the specialty pens. Some office supply stores might carry them as well.
Invisible Ink Pens and Markers
Secret Messages on the Walls
- Glow in the Dark Experiments and Activities
Light up the night with these awesome glow in the dark activities and experiments. Make glowing drinks and a glowing geyser. You can even make glow in the dark writing that is invisible in the day.
Glow in the Dark Writing
- Petroleum jelly
You can make writing that glows in the dark using petroleum jelly. The writing will be hard to see under normal lights.
Using your fingers or a q-tip, write a message with the petroleum jelly. You can write it on white walls if you don't want it to be very obvious. Or you can write it on a piece of paper for easy clean-up.
Smooth out any bumps or excess spots in the petroleum jelly as you write. The smoother you make the message, the more invisible it will be in normal light.
Then turn out the regular lights and flip on a blacklight. The writing will glow in the dark!
Some detergents, B-vitamins, tonic water, honey, and toothpaste with whitener will also glow in the dark.
This is a great trick for mystery parties or CSI-type parties. It is also fun for Halloween or just leaving fun secret messages.