I have a shelf that was supposed to hold reference books. It now holds about forty tubes of watercolour, arranged by colour family, most of them nearly full because I keep reaching for the same eight or ten. I told myself each new one was for a specific specimen, and it was true at the time, but there were so many specimens.

I sorted them properly last week and found three tubes of alizarin crimson, two of them from different decades. That gave me pause.

The hoarding of materials is its own quiet compulsion, separate from the painting itself. I think we all know this. I am not quite ready to call it a problem. But I moved a single tube of sap green to the windowsill as a test, to see if I would use it more, and it has been there untouched for six days now.