what is iron gall ink
Oak galls and iron(II) sulfate, ingredients of iron gall ink. Iron gall ink (also known as iron gall nut ink, oak gall ink, and common ink) is a purple-black or brown-black ink made from iron salts and tannic acids from vegetable sources.hile a very effective ink, the formula was less than ideal. Iron gall ink is acidic ranging from roughly equivalent to a lemon (pH â 2) to that of a cup of black coffee (pH â 5).