One other thing about Iroful -
Of the seven or so inks I've used so far in the notebook, there was one, Noodler's Walnut, that seemed to take a reeeeally long time to dry. I left the page open for about an hour before putting the notebook away.
The following day, I then wrote on the other side of the Walnut ink page, with a different ink. I found that the pressure of my writing actually worked like a carbon paper- the walnut ink transferred in many spots onto the blank page it was lying against. !
(Note that this Noodler's ink is not ACTUAL walnut ink, it's just named for the color of it)
So, I've learned not to trust things, and I now put a simple piece of loose paper in back of whatever page I am writing on, to totally avoid any possible 'carbon copy paper' effect. A simple enough solution and a good practice in general i think, not unlike taking the time to wash one's hands before writing, drawing, or painting on lovely paper.