Name: Al S.
I am currently reviewing old recipes of ink making
specifically iron gall ink. I have found a recipe calling for the use of
iron dissolved in acetic acid and not the regular ferrous sulfate. It
claims it to be more permanent. I have myself experimented with both
inks and found the first one to be very water resistant whereas the latter
much less so. Can anyone please explain this? and also does this have
any bearing on the long term permanence of the ink?
The acetate salt of Fe(+2) evolves acetic acid (vinegar) when it dries
(especially if it is heated). This results in the formation of (probably)
iron oxides and/or iron salts of organic acids present in the paper or
canvas. Hence is forms a "faster" color (to use the jargon) than the sulfate
salt which remains water soluble because the sulfuric acid is not volatile
and forms a permanently soluble residue.