This medieval ink starts with a wasp.

In spring, it punctures the soft young buds of the oak tree and lays her eggs. The tree, in response, forms little nutlike growths around the wasp holes, and it is these protective oak galls which form the basis of an intense black.

It was the standard writing and drawing ink in Europe from about the 5th century to the 19th century and remained in use well into the 20th century. The process was probably learned from the Arabs, who used it for ink, cloth dyeing and mascara.

The ink was prepared by fermenting the crushed oak galls in water to release the concentrated brown gallotannic acid. Adding green copperas (iron sulfate) helped darken the ink further and aid in permanency.

After ltering, the ink had a binding agent of gum arabic added to control the ow from nib or brush. A well-prepared ink would gradually darken to an intense purplish black. The resulting marks would adhere rmly to the parchment or vellum, and (unlike india ink or other formulas) could not be erased by rub- bing or washing.

In the UK it is still used in Registrars’ Ink for all of cial documents of birth, marriage and death certi cates.