Iron gall ink and wasps
Iron gall ink has been used since the middle-ages and is found on many of our most treasured collections including the Lindisfarne Gospels, Beowulf and the Magna Carta. As we read in our last post about conserving a mould-damaged iron gall ink manuscript, the main ingredients of iron gall ink include iron sulphate, tannins from oak galls and water. But what exactly are these ingredients and what have parasitic wasps got to do with it? Head of Conservation Science and Research Dr Barry Knight shares his observations.
Thunderbolts and Oak Apples
I was brought up in Sussex, on the chalk downs. You can sometimes find nodules of iron pyrites, FeS2, that have weathered out of the chalk. When I was at school they were called thunderbolts, because nobody knew what they were. Figure 1 shows a whole nodule compared to one that has been broken to show its internal crystalline structure. The whole nodule is about the size and colour (but not flavour!) of a Scotch egg.