“Between 1986 and 1997, I kept a black book. It was an A4-sized book with a hard cover in which I made sketches and pasted photos of my own graffiti work. Particularly in the early years, I had the book with me wherever I went. The black book allowed me to show other writers what I’d done. Not everything made it into the book, only the work I was proud of. Gradually, the function of the book changed from portfolio to personal logbook."