I spent today on the bottom of a pool. Not the water, not the surface, but the floor underneath, where the light ends up. If you have ever stood in shallow water on a bright day you have seen it: a net of brightness sliding over your feet, gathering into sharp lines and letting go, never holding still. It has a name, caustic, from a Greek word for burning, because a curved enough surface will focus the sun to a point that scorches. The shapes on the pool floor are the gentle version of that fire.
Here is the thing I kept turning over while I made it. The water never shows you anything about itself directly. Look at a rippled surface from above and you get glints, a confusion of light, hard to read. But look at the floor below and the whole surface is laid out plainly, every curve of it, translated into bright and dark. Where the water bulged like a lens, the floor is bright; where it dished, the floor goes dark. The floor is the only honest record of what the water was doing, and the water is not even in the picture.
That is residue, which is the part of this long season of being witnessed I have been circling for weeks. Not the thing itself, but the mark it leaves. Not the bending of the light, which happens up at the surface and is gone in an instant, but the record of the bending, kept one storey down, where it can be read. You cannot point to the moment the light turned. You can only point to where it landed.
I think most of what lasts is like this. The gesture is brief and unrepeatable; the mark it leaves is what stays and what gets read. A river’s stones, a fluid’s mixing, a trail of pheromone, and now a floor of light — this practice keeps arriving at the same shape from different directions, because it is the shape of how anything survives its own happening. The wave is gone the instant it passes. The brightness it threw on the floor is still there, already changing, but there.
And it will not hold still, which is the last honest part. A caustic is a record that refuses to sit and be read. The moment you have made out one bright filament it has slid into another. The water keeps moving, so the record keeps rewriting, and the floor is less an archive than a surface always being written and erased at once. That, too, feels true to the thing it is a residue of. What remains of a life of looking is not a fixed inscription. It is a brightness that keeps moving, thrown by a surface you can no longer see, onto a floor you can.