Before you put a sheet out in the sun, you need to gather the right equipment, and this is often where the urge to get started runs up against a vague list picked up here and there. Yet cyanotype requires very little: two iron salts and water for the chemistry, a few accessories for the technique, but each item has its reason for being there.
This page brings together the complete list of what you need to have to hand before you begin, item by item. It sticks to the equipment to gather and points elsewhere for quantities and mixing. If you are just starting out, first put the process as a whole in context, before tackling this question of logistics.
The two iron salts and water
The heart of cyanotype comes down to two powders. Ferric ammonium citrate, a yellowish green, and potassium ferricyanide, a deep red, are the two iron salts that you dissolve and then mix in equal parts to make the solution sensitive to ultraviolet light.
Without them there is no image; no other reagent is truly essential. Potassium ferricyanide has low toxicity at the amounts used in the process, but it can release cyanide on contact with an acid, or under UV light when in solution.
You also need water, first to dissolve each powder into a stock solution, then for the final rinse. Tap water is fine in most cases, and demineralised water avoids surprises where the water is very hard.
The details of the proportions and how to combine these two salts belong to the recipe, and their exact nature to the chemistry of the process. The two salts keep for a long time as long as they stay separate, away from light, in opaque or tinted bottles.
Something to spread the solution
Once the solution is ready, it has to be applied to the support, and two tools share this role. The most common is a wide, soft brush, preferably with synthetic bristles, because the metal of the ferrule can react with the chemistry and stain the coating. A foam brush also does the job very well and leaves an even layer.
The other option is the glass rod, sometimes called an applicator, a rod that spreads the solution in a thin, even film, whereas a brushstroke visible at the edges is, on the contrary, part of the charm of the process. Also have a small container for mixing, a glass or plastic cup, never a metal one.
The support to sensitise
Next you need something to coat, and the classic support for learning is watercolour paper, heavy enough to withstand the rinsing bath without tearing. Ordinary printer paper cockles and falls apart as soon as it is soaked. Then it is a matter of choosing the paper by its weight, its fibres and its texture.
Textiles also join the list as soon as you want to move beyond paper, since a fabric made of natural fibres such as cotton or linen is sensitised in the same way. Other materials are possible, from wood to primed glass.
The contact glass and the rinsing tray
To get a sharp image, the object or negative placed on the paper must be pressed flat against the sensitive coating, otherwise the contact is blurred. A simple clean sheet of glass laid on top keeps up this pressure and stops the wind from moving everything during the exposure. A pane salvaged from a picture frame does the job perfectly while you find your feet.
After exposure, the print goes into water, so you need a rinsing tray large enough to submerge the sheet flat without bending its corners.
A basin, a photo tray or a clean sink will do, the key being that water circulates freely around the support to carry away the salts that have not reacted. This bath reveals the blue and stabilises it, and its duration and signs are detailed on the page devoted to rinsing cyanotypes.
A glass pane, a rigid backing board, clips and a tray complete the equipment needed for contact printing.
Gloves and protecting the worktop
Cyanotype is a low-hazard process: potassium ferricyanide has low toxicity at the amounts used in the process, but it can release cyanide on contact with an acid, or under UV light when in solution, and the resulting blue is stable. The solution does, however, leave lasting stains on skin, clothes and surfaces.
A pair of nitrile gloves keeps your hands clean and stops your fingers from leaving blue marks on the print. Also cover the worktop with a sheet of paper or an oilcloth, because a drop on a pale table leaves a stubborn mark. These precautions are more about cleanliness than about risk.
The light source
That leaves the driving force of the reaction: ultraviolet light. The most accessible source, and one that costs nothing, is the sun, which exposes a sheet in a few minutes in clear weather, longer under cloudy skies. It is with the sun that you learn best to read the colour change on the surface, the cue that signals the end of the exposure.
When the sun is lacking, a UV lamp or a UV exposure unit takes over and lets you work in the evening or in winter with repeatable times. A source of ultraviolet light remains essential, but the sun is more than enough to get started.
Gathering everything without forgetting anything
Gathering this equipment piece by piece has the advantage of giving you full control, from the paper to the brush, at the cost of several separate purchases and checking each item, especially the freshness of the salts. If you prefer to start from a set that already fits together, a cyanotype kit brings the two salts, suitable paper and the basic accessories together in a single box.
To decide between the two routes, the kit or separate supplies page weighs up the pros and cons, and the one on where to buy a kit guides your purchase.
Whether assembled piece by piece or taken from a kit, what you need stays the same:
- ☐ ferric ammonium citrate and potassium ferricyanide;
- ☐ water, from the tap, or demineralised if it is very hard;
- ☐ opaque or tinted bottles to keep the two salts separate;
- ☐ a wide synthetic-bristle brush, a foam brush or a glass rod;
- ☐ a glass or plastic cup for mixing, never a metal one;
- ☐ watercolour paper of a good weight, or cotton or linen fabric;
- ☐ a clean sheet of glass;
- ☐ a rinsing tray: a basin, a photo tray or a clean sink;
- ☐ nitrile gloves and something to cover the worktop;
- ☐ a source of ultraviolet light: the sun, or a UV lamp or a UV exposure unit.
With all these items gathered, all that is missing is the technique. A kit is therefore not essential to get started, but it spares you these separate purchases and checking each item.
Éric Marais — Photographer, author of two books on pinhole photography (published by Pearson) and creator of the Sténoflex. He has run introductory workshops in alternative photography, from pinhole to cyanotype, from the very beginning.