Why do we use indelible ink during elections?

We always like to flex our purple-tinted fingertips after voting, but why do we use indelible ink during elections anyway?

On election day, Kuya Kim shared a trivia live on air, explaining that this is used to avoid double-voting.

The indelible ink, also called electoral ink, has seven percent nitrate in its composition, and cannot be erased using ethyl alcohol, gasoline, soap, bleach, acetone, or brake fluid.

It remains on one's skin for 72 to 96 hours, and it could stay on one's nail for up to a month.

This ensures that a citizen cannot vote more than once during the voting period.

It was first used during India's 1962 elections. —JCB, GMA News