CYANO - Cyanotype Photos

Every colour becomes the wrong brightness. Yellow goes black, blue goes to bare paper. That is what a cyanotype does, and now your camera roll can do it too.

Cyanotype is the oldest surviving photographic process, and the reason old engineering drawings are called blueprints. Paper is brushed with iron salts, a negative is laid on top, and it is left in the sun. What develops is Prussian blue, in water, with no darkroom and no chemistry set.

CYANO does the chemistry in software.

This is not a blue filter. A cyanotype is blind to red and green and sees only ultraviolet and deep blue, so it renders the world at the wrong brightness. That is the whole point of it. A bright yellow sign goes almost black. Green leaves go dark. A blue sky burns straight through to bare paper, taking the clouds with it. Two colours your camera recorded as equally bright come out at opposite ends of the print.

Everything here is simulated from the physics rather than approximated with a preset. The sensitiser's response is integrated against sunlight across the spectrum, the pigment is built up through the Beer-Lambert law with the way it clumps at high concentration accounted for, and the tonal curve falls out of the photochemistry instead of being drawn by hand. What you get is what the paper would actually have done.

And it reads each photograph before printing it, the way a printer reads a negative and makes a test strip, so the exposure suits the picture in front of it rather than some average one.

WHAT YOU CHANGE

Sun: how long the print was left out. Overexpose it and the shadows merge into one mass, the way they really do.

Bath: tea, green tea, coffee, wine, tannin, washing soda, or a split bath. Each turns the Prussian blue into another pigment, which is why a toned print reads as a different process and not a recoloured one. Tea, coffee and tannin stain the paper too.

Paper: cotton rag, rough watercolour, buff, linen or washi. Each has its own surface, and it shows through everywhere, because in this process the paper is part of the picture.

Edge: clean, brushed, or the whole sheet with the brush strokes running past the picture. Every sheet is brushed differently, so two prints of the same photograph are never quite the same.

Image: a positive, or a negative.

Formula: the classic 1842 sensitiser, or the modern one, which holds its shadows deeper.

Then watch it develop: out in the sun, into the wash, into the bath.

The app prints at full resolution, keeps nothing, and puts no mark on your pictures. There is no account, no subscription, and nothing is sent anywhere.