This is a question which i've asked myself on many an occasion... My best guess is that it was Kohl - but cunningly mixed with Perilla oil !
It was common enough at the time : The plant being used for cooking and whatnot - but most importantly the oil was used in waterproofing cloth.
Jack probably knew this as waterproofing was necessary on a boat, and genius that he was - adapted it for his own custom eyeliner.
Are you saying you think I'm wrong?
Lookie all the facts about perilla - linkage
I think the mystery of the waterproof eyeliner is solved!!!
It's L'Oreal obviously ...
LOL, no um, from what I've heard, obviously in the movies they just use eyeliner and make up, but apprently it's coal, I mean like charcoal/ash from the remnants of a fire ... which is why the colour is always described as 'KohlBlack'. The other thing I head is that the eyeliner was drawn on much in the same way that tatoos are done and that it's permanent.
I'll have a dig around and see if I can find anything out!