DIY: Invisible Ink | Tinkerer Box Blog

DIYs » Stem Activities » Chemistry » Age 6 - 8 » Invisible Ink

Invisible Ink

Stem Activities

Ages: 6-8

Greater than 30 minutes

Grownup needed

Save PDF

Have you ever dreamed of having mysterious invisible ink that makes your drawings disappear on ordinary paper, only to be revealed through special methods? In this science experiment, we'll not only make invisible ink but also make it glow with a magical fluorescent effect. Let's see how it's done!

Materials Needed

Baking soda
Cotton balls
Water
Glass
Lemon
Knife
Paper
Highlighter pen
Spoon
Dropper
Scissors
Paintbrush

Various materials are laid out on a light woodgrain table, seemingly for a science experiment or art project. Two clear glass bowls contain white substances: one appears to hold baking soda or a similar powder, while the other contains several cotton balls. A small glass beaker with a wooden handle holds a clear liquid. An empty clear glass jar, a whole lemon, a small knife, two yellow markers or paintbrushes with caps, a small black measuring spoon, a clear pipette or dropper, a pair of scissors, a paintbrush, and a blank white sheet of paper complete the arrangement. This flat lay suggests preparation for an activity involving invisible ink, citrus-based reactions, or a similar scientific or artistic endeavor.

Step-by-step tutorial

Step 1

Use scissors to take apart the highlighter pen and remove the ink cartridge.

A hand holds a pale yellow marker horizontally above a light woodgrain surface. The marker is being cut near its tip with a pair of scissors held in another hand. The focus is on the action of cutting the marker, with the scissors blades positioned to sever the plastic casing. The marker has some text visible, suggesting it's an art or craft supply. This image likely demonstrates a step in a DIY project or experiment involving modifying a marker, perhaps to extract ink or create a custom nib.

Step 2

Place the ink cartridge in the glass, use the dropper to draw up two millilitres of water, then position the cartridge vertically and drop the water into it.

A hand holds a bright yellow marker upright over a clear glass beaker on a light woodgrain table. A plastic pipette dispenses drops of a clear liquid onto the exposed, cut end of the marker. The beaker appears empty or contains a small amount of a clear solution. This close-up image suggests a scientific experiment or DIY project involving the absorption of liquid by the marker's inner core, possibly to create a custom color or effect.

Step 3

Wait patiently until the highlighter ink is washed out by the water and the cartridge becomes colourless.

A small, clear glass beaker sits on a light woodgrain table against a plain off-white background. The beaker contains a vibrant, fluorescent yellow liquid, filling the bottom portion of the vessel. A 60mm marking is visible on the beaker's side, likely indicating its diameter. This simple image suggests a scientific experiment or demonstration involving a chemical reaction or solution, highlighting the vivid color of the liquid.

Step 4

Cut the lemon using the knife.

Two hands are shown in the process of cutting a lemon on a light woodgrain surface. One hand holds the lemon steady while the other uses a small knife with a gray handle to slice through it. The lemon is bright yellow and appears ripe. The focus is on the act of cutting, with the knife positioned midway through the lemon. This image likely depicts a step in a recipe or experiment requiring fresh lemon juice.

Step 5

Add lemon drops to the fluorescent ink until it becomes pale or colourless. Your invisible ink is now ready.

A hand squeezes a cut lemon half over a small, clear glass beaker containing a bright, fluorescent yellow liquid. The beaker sits on a light woodgrain surface. Drops of lemon juice are visible falling from the lemon into the beaker. This image suggests an experiment or demonstration where lemon juice is being added to a pre-existing solution, likely to observe a chemical reaction or color change.

Step 6

Add lemon drops to the fluorescent ink until it becomes pale or colourless. Your invisible ink is now ready.

A blank white sheet of paper lies on a light woodgrain table. A hand is partially visible, dipping a small paintbrush or similar tool into a clear container filled with a pale yellow liquid. Another hand rests on the edge of the paper, seemingly holding it in place. This image suggests an art project or experiment involving applying the liquid to the paper, likely to create a design or observe a reaction.

Step 7

Next, add one teaspoon of baking soda to 60ml of water and mix well.

A black plastic measuring spoon filled with white powder, likely baking soda or a similar substance, is positioned above a small glass beaker. The beaker contains a clear liquid, possibly water or vinegar, and some of the powder is already visible at the bottom of the beaker, suggesting it's being gradually added. The beaker sits on a light woodgrain surface and has milliliter and ounce markings on its side. The image likely depicts a science experiment or kitchen task involving the mixing of ingredients.

Step 8

Use scissors to grip a cotton ball and soak it in the baking soda solution. Brush the dried paper from step 6 with the cotton ball. Watch the magic happen!

A hand partially visible in the bottom left corner holds a piece of white paper against a light woodgrain table. The paper has a few faint, light-colored markings on it, possibly from a liquid or light heat exposure. The focus is on the paper and its subtle markings, suggesting the result of an experiment or a creative process.

The Science Behind It:

Objects with higher density sink, while those with lower density float. Salt water has a higher density than food colouring, so the colouring floats on top of the salt water. However, since food colouring has a higher density than plain water, it slowly sinks in the cup of plain water.

Who Are We?

We’re a passionate team of scientists, engineers, and educators dedicated to delivering hands-on fun. Our mission is to inspire creativity and confidence in the next generation of young innovators.