Acrylic ink is generally a pigment or dye in an exceedingly low viscosity acrylic binder. You can paint with it, or use it with paint as part of a larger work, or you can use it as ink. That’s what I’m doing now. I’ve picked up some Daler Rowney acrylic ink and I’m using it in my Indigraph pen. It’s a pen that can use india or any pigment based ink without drying out and becoming unusable.
I picked up sepia. Daler Rowney’s sepia is a semi-opaque, pigment ink using PBk7, PR112, and PY1:1 for a nice rich brown sepia. It’s less red than I expected, really only having worked with sepia pencil before this. Anyway, I like it. Turns out acrylic ink dries fast, so fast I thought maybe it was because the pen. So I tried it in a boring old dip pen and it still dries “instantly” for all intents and purposes. Seriously, 3 seconds (didn’t I tell you 3’s are events after all), about the time it takes me to set down a pen and pick up a brush and the stuff’s dry.
Apply it really heavy, going back and forth over an area a bunch of times and that turns into half a minute, but that’s still fast as heck. Three days in and it still flows immediately when I pick up the Indigraph so I’d say I’ll be using acrylic ink for the time being.