The use of iron-gall complexes in ink and for dyeing or printing textiles is compared to degradation phenomena, which are well-known in ink corrosion on paper. Definitions of a dyestuff and a pigment are given and the general properties and classification of dyestuffs are described. The differences between dyeing wool or silk and linen or cotton (printing chintz) black are considered, from an historical point of view, with a focus on working practice in The Netherlands. It is concluded that black-dyed textiles suffering from degradation were not processed properly, whereas ink corrosion stems from the acidity and the iron (II) content of the uncorrected ink, when the ink was applied. -- SCMRE