It's a Pip
An It's a Pip liquid made of special latex ink was devised by Caryl Fleming and Charles W. Fricke (Judge) in 1937 (See ad in The Linking Ring, Vol. 17, no. 7, september) to accomplish the It's a Pip effect. It is no longer manufactured, in large part because much (but by no means all) of its applications can be accommodated by dry erase markers.