A student left it behind three years ago when I still taught the Tuesday group, and it's been sitting on the shelf above the palette table since. The linseed has separated, there's a skin on top like the surface of old milk, and underneath it the paste has gone the colour of an old piano key. Not white. Warm.

I know what lead white does. Creminitz wrote about it, everyone wrote about it, it darkens and the world moves on. But this jar is the last of it I will probably ever have. Nobody sells it to a studio painter here now, and I am not going to order it from a restorer's supplier like some kind of criminal.

Part of me wants to use it. Not as white, as a warm pale for flesh in shadow, mixed with a touch of terre verte, and let it do whatever it does over ten years. The other part knows I'd be painting something I'll be apologising for in 2035.

I put my nose in it this morning, the way you do. Still smells of nothing much. That's the strange part, it doesn't smell like metal or dust, just faintly of oil.

So it sits there. I pick it up, I look at it, I put it back. It's become a kind of ornament, which is the worst fate for a material. If anyone paints in lead and has an opinion on whether a three-year-old paste is worth reviving with a bit of fresh oil on the glass, I want to hear it.