I just had a comment from a friend that of course my writing sample washed away in water because it was dye ink. That got me thinking. If it was dye it wouldn't wash away because by definition dyes bond to the substrate. To my thinking, if something colored doesn't stick, then it's not a dye but just a colored material like pigment, only a soluble one.

So I checked a couple of internet sources.

Britania
"Dye, substance used to impart colour to textiles, paper, leather, and other materials such that the colouring is not readily altered by washing, heat, light, or other factors to which the material is likely to be exposed."

Wikipedea
"A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color."