I keep a small notebook beside the board for every painting. Not the finished work, the process: pigment, brand, ratio, paper batch, the temperature of the room, and a one line verdict on whether the wash behaved. It is a habit left over from the laboratory and my students find it faintly ridiculous, but it has saved me more than once.

This morning I was laying a first wash of French ultramarine over a hellebore leaf, thinned further than I usually dare, and it bloomed at the tip exactly where the veins tighten. I checked the log. The same thing happened in November, same paper, same paper batch stamp, same dilution, and I had written "too wet for this sheet, size it first" and then evidently forgotten.

Two hundred and fourteen pages and I still repeat a mistake I had already identified and written down in my own hand. The log is honest. I am not always.

I have started underlining anything that went wrong, so at least the failures are the things my eye catches first when I open to a new page. It feels a little like keeping a book of my own errors on purpose. Which, I suppose, is what it is.