The instrument
Spill responders estimate how much oil is on the water by looking at its colour. The scale above is theirs — the Bonn Agreement Oil Appearance Code — and every band on it is drawn with the same interference formula the works use, not picked by hand. Iridescence lives in one narrow window. Below it the film is silver. Above it, metal, then brown, then black.
Volatiles evaporate in hours, so the film thins and slides into the rainbow window — the work is more beautiful after a day than at the moment it was poured. Then it oxidises, and the colour dies for good, and what is left is residue: brown, matte, permanent.
Underneath, the work runs on a slower clock. The binder yellows, the titanium dioxide that makes the pearl eats the binder from the outside, and each material chalks into its own oxide — copper stays warm, chrome goes neutral, the mica goes white. Nothing converges.
A film of crude oil on water is a few hundred nanometres thick. Light bounces off its top face and its bottom face, the two waves meet, and whichever colour survives depends on one thing only: how much oil is there.
So the beauty is a dose. Under 0.3 µm the slick is a silver sheen. Between 0.3 and 5 µm it is the rainbow everyone has seen in a car park puddle. Over 5 µm the orders of interference pile up inside each colour channel and cancel — the film goes metallic, and the rainbow is gone. Not faded. Gone, because there is too much.
These works start clean. The owner pours the oil, with a finger or a mouse, wherever they like. The stain spreads on its own under its own weight, the way a viscous film spreads on a liquid less viscous than itself: the front breaks into fingers, never a circle. Each touch weighs more than the last.
Touching the part that already glows is what kills it — the film thickens past the window. And 62% of every pour is asphaltene and resin, which does not evaporate. It thins, it stops, and it stays. The covered area only ever grows.
Whoever opens the work sees the same oil, in the same places, at the same age, from any device. The gesture is recorded, not the picture — three numbers, six bytes: where, where, when. The work is rebuilt from the list of what was done to it.
Left alone for a decade, the oil is the most stable thing on the canvas. The materials underneath corrode, chalk and darken; the film has nothing left to lose. The contamination outlives what it contaminated.
For scale
Appearance-to-thickness bands follow the Bonn Agreement Oil Appearance Code, used for aerial estimation of spill volume. Coverage figure is the standard sheen arithmetic: 1 m³ spread at 1 µm covers 10⁶ m², so 1 litre covers 10³ m².