Creating an invisible ink pen using a highlighter involves extracting the fluorescent ink and then modifying it to become invisible until revealed under UV light. Here's a breakdown of how to do it:
Steps to Create the Invisible Ink Pen:
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Disassemble the Highlighter: Carefully take apart the highlighter pen. The goal is to remove the ink reservoir (usually a felt or fiber component) from the plastic casing.
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Extract the Ink: Place the ink reservoir in a small container (a glass or plastic cup will work). Add a small amount of water to the container. The water will help to dissolve and extract the fluorescent ink from the reservoir. This may take a few minutes; gently agitate the reservoir in the water to speed up the process.
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Neutralize the Color (Make it Invisible): Add a small amount of lemon juice to the extracted ink solution. Lemon juice contains citric acid, which reacts with the dye molecules in the highlighter ink and converts them to become less visible under normal lighting. This step is crucial to making the ink invisible. Start with small amounts and add more if needed.
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Create the Pen: Now you need a delivery system. You have a few options:
- Reuse the Highlighter Casing: Clean out the original highlighter casing and refill it with your new invisible ink. You may need to replace the original writing tip.
- Use an Empty Pen: Acquire an empty pen cartridge or a refillable pen. Fill the cartridge with the invisible ink.
- Cotton Swab/Brush: For a simpler approach, use a cotton swab or a fine-tipped brush to apply the ink directly to the paper.
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Testing the Ink: Write or draw on a piece of paper with your invisible ink pen. Under normal lighting, the writing should be nearly invisible. Shine a blacklight (UV light) on the paper, and the writing should glow brightly, revealing the message.
Explanation of the Chemistry
The highlighter ink contains fluorescent dyes that absorb ultraviolet (UV) light and then emit visible light, causing the glowing effect. The lemon juice (citric acid) changes the structure of the dye molecules. This change significantly reduces the visible color under normal light, making it appear invisible. However, the modified dye still reacts to UV light, causing it to fluoresce, thus revealing the hidden message.
Important Considerations:
- Safety: Although this process is generally safe, avoid getting the ink or lemon juice in your eyes. Wash your hands thoroughly after handling the materials.
- Ink Concentration: The amount of water you add will affect the ink's concentration. Too much water will dilute the ink, making it less visible under UV light.
- Paper Type: Some papers may show the ink better than others. Experiment to find the best type of paper for your invisible ink.
- Lemon Juice Amount: Adding too much lemon juice can completely destroy the ink’s fluorescent properties, so add it incrementally and test.
- Alternatives: Other acids like vinegar can also be used instead of lemon juice, but lemon juice is often preferred due to its availability and relatively mild acidity.
