Indelible ink’s new challenger: invisible ink

• Indelible ink, the purple stain that billions of Indians show off during elections, may face an invisible challenger in the near future.

Key highlights

• The Delhi-based National Physical Laboratory (NPL), the creator of indelible ink, has a new concoction that, when applied on the finger, doesn’t leave a trace it merely glows a bright orange when a low-intensity beam of ultraviolet light is shone on it.

• The NPL prepared the ‘invisible ink’ as part of a pilot project mooted by the Mysore Paints and Varnish Ltd. (MVPL).

• “The MVPL discussed with us the development of such an ink for use by a client in Europe,” said Dinesh Aswal, director, NPL.

• The indelible ink was formulated as a deterrent against voting twice.

• But strangely enough, voters in some countries found the stained finger rather unseemly.

• “In India, we are proud to display our voter’s ink, but apparently in some countries people don’t want to display such a mark.

• So MVPL asked us if there was a solution,” said Mr. Aswal.

Organic-inorganic mix

• The NPL’s invisible ink, however, wouldn’t be of immediate use to the EC.

• “The current formulation can’t be used for Indian elections as they are spread out over many weeks.

• We would need a different formulation,” said Mr. Aswal.

• He described the chemical a transparent liquid — as an “organic-inorganic” mixture that was biodegradable and could be washed off in 48 hours.”

• The ink works on the well-known principle of fluorescence — certain materials emit a characteristic glow when exposed to ultraviolet light.

• The NPL ink, however, glows only when exposed to a narrow band of frequencies of ultraviolet (UV) light. “Commercial UV markers or inks respond to a very broad spectrum of UV light.

• The NPL’s invisible ink experiment is linked to a larger project of creating security inks that could be used to make bank notes and documents, such as passports, more secure.


Prelims level: Indelible and Invisible ink- Chemical composition

Mains level: Not Much

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