For images that have been reproduced for more than a century and looked at, quite intently, by millions of people, there is a great deal of secrecy surrounding the Rorschach ink blots. These famous cards – both intensely guarded and instantly recognisable – continue to be used for psychological diagnosis around the world. New copies are only printed every five years or so, and no one has ever been allowed to document the process. So when I asked the publisher recently if I might do so, I had not expected them to say yes. There were conditions, of course: the most perplexing of which was that if I were to document the printing of the Rorschach ink blots, I must do so without revealing any information about the printing of the Rorschach ink blots. It seemed a test as exquisitely elegant as the one for which the cards themselves are used.

The ink blots are named after Hermann Rorschach, a Swiss psychologist who died so young that he only makes it halfway through his biography. One Sunday in late March 1922 he is taking his wife Olga to see Peer Gynt at the theatre and a week – five pages – later he’s dead. He had been born in Zürich 37 years earlier, the first of three children – two boys and a girl – to Philippine and Ulrich. His father was an extremely skilled artist and wrote a 100-page treatise titled Outline of a Theory of Form in which he considered many aspects of visual perception, asking: “Who among us has not often and with pleasure turned our eyes and imagination to the ever-changing shapes and movements of the clouds and the mist?”. Hermann became a gifted student and joined the elite academic Gymnasium in Schaffhausen, northern Switzerland. His skill as an artist was perhaps his defining characteristic, however, and led to his admiringly mocking nickname of Klex, a shortening of klexen or klecksen, which means something like “to daub”. Klex also means ink blot.