From UPSC perspective, the following things are important:
Prelims level: Indelible and Invisible ink- Chemical composition
Mains level: Not Much
- 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
- The ink was first used during India’s third General Elections in 1962. Indelible ink has been used in every General Election since
- 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.
- Indelible ink is made of a chemical compound called silver nitrate.
- When applied to the skin and exposed to ultraviolet light, it leaves a mark that is almost impossible to wash off.
- The stain is so strong, in fact, it is only removed when the external skin cells are replaced
- When put on the skin, silver nitrate reacts with the salt present on it to form silver chloride.
- Silver chloride is not soluble in water, and clings to the skin. It cannot be washed off with soap and water.
Issues with it
- 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.
- The NPL prepared the ‘invisible ink’ as part of a pilot project mooted by the Mysore Paints and Varnish Ltd. (MVPL)
- It is a transparent liquid as an organic-inorganic mixture that was biodegradable and could be washed off in 48 hours.
- It 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.
- 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.