This review is part of a series of "blues reviews". I was fortunate enough to obtain a bottle of Sailor's custom ink for Bungbox 4B through Vanness while they had some. The papers are Mohawk via Linen, Hammermill 28ln inkjet, and Tomoe River.
The ink appears to be a single dye, similar to pthalo blue.
Reasonably waterfast. Note: one should also mop up water on an inky page with a paper towel, and one should blot up the water. Using a tissue is an error as these do not mop up the water well. Also, do not wipe as this causes the ink to spread and may obliterate your writing.