What is the ingredient of the indelible ink used during the process of voting?

Indelible ink is the one which is used during the process of voting in India. It is applied on the forefinger of voters after they have cast their vote in order to ensure that they do not do it again. It was in 1962, when the Election Commission of India together with the Ministry of Law, National Research Development Corporation and National Physical Laboratory of India entered into an agreement with the Mysore Paints and Varnish Ltd. for manufacturing of a type of ink which will not be able to wipe off with ease. The Paint company is the only supplier of the ink to the governmental body and is used both in the State and General Elections. It came into being in 1937 Maharaja Krishnaraja Wadiyar IV. Mysore Paints now also the supplier of ink to 25 countries of the world. The best part of the indelible ink is that it stays on for 10 days and stands to fade away. The ink contains silver nitrate and is manufactured secretly.