Granny never knew until recently that those little spherical, corky growths on Oak trees that we know as oak 'apples', formed in response to the developing larvae of a gall wasp, had played such an important part in our written history. How? Because for centuries those little spongy balls have been collected for the manufacture of oak gall ink.
Also known as common ink, standard ink, or iron gall ink, it is purple-black or brown-black and made by mixing iron sulphate (Vitriol), tannic acid - usually from oak galls - and gum Arabic. Recipes varied greatly, but it was the standard ink formulation used across Europe for fourteen-hundred years between the 5th and 19th centuries and remained in widespread use well into the 20th century.
The earliest recipes for oak gall ink come from Pliny the Elder and there are many available today on the internet should you wish to make your own! A good ink, gradually darkening to intense purplish black is indelible, adhering firmly to the parchment or vellum it is written on. Well-made vellum, usually of calf-skin, has had its fat scraped from the skin and the dense mat of collagen fibre left has been stretched and dried under tension. It needs to be kept in carefully controlled humidity to prevent deforming.
Laws passed in Great Britain and France specified the content of iron gall ink for all royal and legal records to ensure permanence. This combination of well-prepared ink and vellum ensured no alterations could be made without scraping into the background and removing a layer, leaving any alterations or interference clearly visible.
The oldest, most complete Bible thought to have been written in the middle of the fourth century was written in oak gall ink and important manuscripts from the Middle Ages and Renaissance as well as many drawings by Leonardo da Vinci survive thanks it its permanence, as do four copies of Magna Carta drawn up in England in 1215.
During colonisation and beyond, the United States Postal Service had its own official recipe for iron gall ink that was to be made available in all post office branches for the use of their customers.
Not until the invention of chemically-produced inks in the latter half of the 20th century did iron gall ink fall out of common use along with its required dipping pens.
When Granny was at school fountain-pens had pretty-well ousted dip-pens and ink pots though we still had an 'ink monitor' for those who could not afford a 'posh' pen. Ball-point Biros, initially frowned on and seen as being bad for handwriting soon ousted the blobby, smudgy writings of both.
Now, I guess most composition and correspondence is done by computer and I wonder how Leonardo would view that?