How does erasable ink actually work?
12.3.2026
Translation: Elicia Payne
Pictures: Stefanie Lechthaler
It makes teachers go insane, but children love it. That’s right, I’m talking about erasable ink. Read on to find out why your writing disappears as if by magic.
In third grade, I was jealous that my classmate Linda had a cool, tribal eraser pen from Pilot. She’d bump up marked exams with her magic wand and turn a grade 4.5 into a 6. And it wasn’t long before everyone else was doing the same. You could see our teacher getting angrier by the day – until she finally banned eraser pens. It’s only taken me until now to realise that the teacher needn’t have worried, because the pen technically isn’t erased.
Erasable gel pens: temperature changes the colour
The rubber at the end of the pen isn’t used to erase the ink, but to heat it up through friction. The temperature causes the ink to change to a colour that reflects all waves visible to the human eye – therefore appearing invisible.
The secret lies in the pigments, in three components to be precise:
Leuco dye: A dye that changes under the influence of heat – just like the thermal paper used for receipts. In its normal state, it’s very light to almost transparent.
Colour developer: The actual colour only appears when it’s added to leuco dye.
Temperature regulator: This makes the colour change when it has reached a certain temperature and doesn’t disappear immediately. That way, you can even write your diary on a hot summer’s day.
When you’re done writing your secrets, you can dye the ink back to its original colour. You just need to cool it down to minus 20 degrees.
Ink eraser: the colour hasn’t really been erased
Just like the erasable gel pens, an ink eraser doesn’t catapult the scribble into the afterlife, it simply changes the colour of the ink. As early as the 19th century, industrial agents were produced in Germany under the names «ink death» («Tintentod») and «eraser water» («Radierwasser») to make writing disappear. This method’s still used today to disrupt the molecular structure of organic ink with chemical substances such as sulphites. This causes the blue colour to stop reflecting until aldehydes reverse the process.
The close bond between pencils and erasers
Things are a little different when you rub out your pencil with a rubber eraser. This is where adhesive force is important – put simply, this is how strongly molecules attract each other. The graphite particles bind to the paper after writing. However, because the eraser has stronger force of attraction, they stick to the rubber and are removed from the paper. Fountain pen ink, on the other hand, penetrates deeper into the paper, and erasers are completely powerless against it – the only thing that helps is Tipp-Ex. Or honesty.
Want to know what the Legami hype’s all about? Find out in Patrick Vogt’s article below.
Header image: Stefanie Lechthaler
Painting the walls just before handing over the flat? Making your own kimchi? Soldering a broken raclette oven? There's nothing you can't do yourself. Well, perhaps sometimes, but I'll definitely give it a try.
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