Election ink

Electoral ink, indelible ink, electoral stain or phosphoric ink is a semi-permanent ink or dye that is applied to the finger of voters (usually the index finger) during elections in order to prevent electoral fraud such as double voting. It is used in countries where voter identity documents were not standardised or institutionalised. One of the more common ink is based on silver nitrate, which can produce a stain lasting several weeks. It was first used during the 1962 general election in India. The ink was developed by the National Physical Laboratory of India, a research institute under the Ministry of Science and Technology of India, and manufactured by Mysore Paints and Varnish Ltd. It is exported to more than 30 countries.