What observation led László Bíró to the key chemical component for a successful ballpoint ink?

Answer

He observed the fast-drying, oil-based ink used in newspaper printing presses

László Bíró was inspired by the instant drying quality of newsprint ink, realizing this fast-drying property was necessary for a reliable ballpoint design.

What observation led László Bíró to the key chemical component for a successful ballpoint ink?
Historyinventorpatentballpoint penwriting instrument