Invisible Ink Experiment (With Lemon Juice & Salt Solution)

Try out this fun easy science experiment of creating invisible ink using lemon juice and salt at home. You can write secret messages and show how oxidation works.

Today we are going to show you – how make your very own invisible ink at home.

Yes, using invisible ink, we can write and leave secret messages like secret agents do!

It is really easy to do and really fun to play with.

DIY Invisible Ink

Materials Required to Make Invisible Ink

You just need to keep the below list of items handy on your work table.

  • Lemon
  • Water
  • Paint Brush or Earbuds
  • Salt
  • Candle
  • Lighter
  • Paper
Things We need for Invisible Ink Experiment

That’s it! If you have the above supplies, then you are good to go to explore this activity.

Directions to Prepare Invisible Ink

We are going to make homemade invisible ink in two different methods using two different key ingredients.

Method-1: Lemon Juice Invisible Ink Experiment

Step-1: Take fresh and ripen lemons and squeeze out the juice using your fingers or any squeezing machine into a small bowl.

Step-2: Now, add a little amount of water into the bowl containing lemon juice. Just 10-15 drops of water are enough. Then, mix or stir the mixture of lemon juice and water using a fresh spoon. That’s it. Our invisible ink is ready to make magical tricks on paper.

start writing Your Message With Lime Juice - Invisible Ink

Step-3: As step-3, Pick a plain white paper and keep it ready on your table for writing a secret message of yours. Then, take a paintbrush and dip it in the bowl containing the lemon juice and water mixture. Here you can also use a cotton swab or earbud to write on the paper.

Step-4: Using the immersed paintbrush, write some text or message of your choice on the paper and let it dry. Once the liquid dried, you cannot see your text completely. So, that is the reason we need to dry the paper properly.

Step-5: As a final step, bring the paper over a heat source, i.e., a candle or lighter or light bulb. And wait for some time until you see the text on the paper appear.

Invisible Ink Experiment with Lemon Juice - Results

Note: You need to make sure the paper is close to the heat source but not too close to avoid catching fire.

Method-2: Preparing Invisible Ink Using Salt

Step-1: Pick a small bowl and add a certain amount of salt. Then, pour some amount of water into it until the salt dissolves completely in the water. You can use this salt solution as invisible ink.

Salt Water Invisible Ink Experiment

Step-2: After you make saltwater in the right proportions, which is our invisible ink, we continue performing the activity same as method-1 from step-3 to step-5.

Heat The Paper to get the message - Invisible Ink Experiment

Step-3: Check the results and observe whether you get the same result as method-1.

Invisible Ink Science Project

Suggested: Explore wonderful science experiments with Salt

Invisible Ink Science Project For Kids

Science Behind Invisible Ink

Lemon juice is a great source of carbon compounds. Since it is an organic substance, it also exhibits oxidizing properties.

These carbon compounds in lemon juice are colorless at room temperature.

However, when they are exposed to heat – these carbon compounds breaks down and release the carbon.

When carbon comes in contact with oxygen present in the air – oxidation occurs. It converts the substance to light or dark brown in color. Prolonged oxidation may even create black color signifying more carbons.

That is the reason your writings on the paper using lemon juice and water mixture turn out into brown color when exposed to the candle.

To make the text written on the paper invisible, we are making the concentrated lemon juice very light by mixing a few water drops.

Diluted lemon juice on the paper gets dry and completely disappears, giving the impression that nothing is written on the paper.

But when you expose to heat or light source, the lemon juice gets oxidized and appears as brown color text. Oxidation is the process of combining carbon atoms with the air and turning light things into dark brown.

Extension Ideas

  1. Try creating invisible ink using other substances such as milk, honey, wine, orange juice and onion juice.
  2. Besides, you can also use other chemical substances that would glow in black light.

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