Indelible ink’s new challenger: invisible ink

Note4students

From UPSC perspective, the following things are important:

Prelims level: Indelible and Invisible ink- Chemical composition

Mains level: Not Much


News

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

Indelible Ink in India

  1. The ink was first used during India’s third General Elections in 1962. Indelible ink has been used in every General Election since
  2. At the time, the country’s election commission was having a tough time dealing with identity theft, as they soon discovered that there were duplicate or fake votes.

Chemical Composition

  1. Indelible ink is made of a chemical compound called silver nitrate.
  2. When applied to the skin and exposed to ultraviolet light, it leaves a mark that is almost impossible to wash off.
  3. The stain is so strong, in fact, it is only removed when the external skin cells are replaced
  4. When put on the skin, silver nitrate reacts with the salt present on it to form silver chloride.
  5. Silver chloride is not soluble in water, and clings to the skin. It cannot be washed off with soap and water.

Issues with it

  1. The indelible ink was formulated as a deterrent against voting twice.
  2. But strangely enough, voters in some countries found the stained finger rather unseemly.
  3. 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.

Invisible Ink

  1. The NPL prepared the ‘invisible ink’ as part of a pilot project mooted by the Mysore Paints and Varnish Ltd. (MVPL)
  2. It is a transparent liquid as an organic-inorganic mixture that was biodegradable and could be washed off in 48 hours.
  3. It works on the well-known principle of fluorescence — certain materials emit a characteristic glow when exposed to ultraviolet light.
  4. The NPL ink, however, glows only when exposed to a narrow band of frequencies of ultraviolet (UV) light.
  5. 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.
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