> Is it that the paper we have now is less compatible? The article describes how the oxidation, which causes the ink to darken, causes a reaction between tanni

> Is it that the paper we have now is less compatible? The article describes how the oxidation, which causes the ink to darken, causes a reaction between tannic acid and these newly created ferric ions. Doesn't that neutralise the acidity? If so, perhaps it is a case of 'survivorship bias' in the old manuscripts which do survive, as they had just the right ratio of tannic acid to iron ions to completely neutralise, whereas the books written with ink containing not enough iron ions would be damaged and discarded.