Mondo Knows Facts
Highlighters glow because the ink fluoresces
A dye absorbs ultraviolet and violet light and re-emits it as visible colour The ink carries a fluorescent dye such as pyranine, which absorbs short wavelength light and emits it at a longer visible wavelength. That added emission makes the marked line look brighter than the page under ordinary light. The ink is water-based and translucent so the printed text beneath stays readable. It sits in Mondo's everyday life collection, one of 200 facts that each trace back to the reference below.
Where this comes from
Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.
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More facts like this
The metal band on a pencil is a ferruleCrimped ridges grip both the wood barrel and the plug of rubberEnvelope gum is a starch adhesive activated by waterDextrin from cooked starch turns tacky when the flap is moistenedHB on standard pencils indicates a balanced medium lead hardnessPencil letters H and B measure graphite hardness and blackness intensityStandard ballpoint pens rely on gravity to feed ink downwardGravity draws heavy ink to the revolving ball tip of common pensBreadcrumbs were used as pencil erasers before rubber was introducedWriters rubbed soft white breadcrumbs over paper to erase pencil marksPost-it notes use low-tack microscopic adhesive spheresWeak microsphere adhesive permits sticky paper strips to peel cleanly without damage
🧭 Everyday Lifefact 171 of 200
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Tags: stationery, colour, chemistry
Highlighters glow because the ink fluoresces: the short answers
- Where does this come from, and can I check it?
- A dye absorbs ultraviolet and violet light and re-emits it as visible colour. The figure is taken from Encyclopaedia Britannica, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
- Is this really a everyday life fact?
- Yes. It sits on the Everyday Life shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
- What else can I read about it?
- The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.