Blue Hour: Cyanotypes from the Raval

Six photographers spent a year printing with nothing but iron salts, paper and Barcelona daylight. What came back is a city rendered in one colour, and it turns out one colour is enough.

The prints hang unframed on wire, close enough that you see the brush edges where the emulsion was laid on by hand. Larger pieces are pinned flat to the north wall, which is where the light does the most work between eleven and two.

Two of the six worked entirely at the river mouth, exposing paper on the sand and washing it in the same water it was printed with. Those sheets carry a tidemark you can read like a contour line, and they are hung low so you can get close to it.

A working table at the back is open on Saturdays: bring a negative or a leaf, and you leave with a print an hour later. The chemistry is mixed fresh each morning and thrown out each evening.

Entry is free before noon. The dye works has no heating, so the room keeps the temperature of the street.