To fix a cyanotype on fabric, rinse it in clean, cold water, changing the baths, often five or six of them, until the water stays clear; if needed, add one tablespoon of white vinegar per litre to the last bath, then wash it cold without alkaline detergent.
A cyanotype on fabric that fades the first time it goes through the washing machine is usually the result of incomplete fixing rather than a dyeing problem. Prussian blue is stable, but it only holds if everything that did not react has been carried away before drying, and if the washes that follow do not attack it.
In short, in 5 steps:
- Rinse in clean, cold water, changing the baths
- Add a little white vinegar to the last rinse if your water is hard
- Dry flat, out of the sun
- Wait twenty-four hours before the first wash
- Wash by hand, in cold water, with a neutral soap
This page sticks to fixing and washing textiles: how to rinse thoroughly, handle the first wash and care for a piece so that it does not fade.
It does not cover the choice of material, discussed in our guide to choosing a fabric for cyanotype, and it complements the method described in the article on cyanotype on fabric. The basics of the process, from the solution to the rinse, are gathered in our cyanotype guide.
Why a cyanotype on fabric fades
On fabric as on paper, exposure turns only part of the iron salts into Prussian blue, the insoluble pigment that draws the image. Everything that received no UV remains as soluble salts, still yellow-green, clinging to the fibres but ready to come out in water, and it is this unreacted share that, if not properly removed, clouds the design.
These two iron salts, ferric ammonium citrate and potassium ferricyanide, sensitise fabric just as they do paper; they are the ones brought together in a cyanotype kit. 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.
The weave holds these residues more deeply than paper does, so a piece dried too early keeps salts deep in its fibres that the first wash then carries away all at once.
Two phenomena therefore need to be told apart. A print that loses its excess salts at the first wash seems to fade when it is actually being cleaned, and a correctly exposed blue stays put. A print that fades wash after wash, on the other hand, is undergoing a chemical attack on the pigment, most often from an alkaline detergent, and that is the case fixing aims to prevent.
The thorough rinse that fixes the image
Fixing a textile cyanotype starts with a far longer rinse than for paper. Rinse the piece in clean, cold water, with no added product, changing the baths as long as the water picks up yellow; on fabric it often takes five or six baths before the water runs clear.
The guide is still the colour of the water, not the clock. Rinse until a fresh bath stays clear in contact with the fabric, because a rinse cut short makes pieces fade.
Handle the soaked fabric gently, pressing rather than wringing, then leave it to dry flat out of the sun; the blue strengthens as it oxidises, just as on paper.
The role of pH and acidity
The stability of Prussian blue depends largely on pH. This pigment copes well with neutral or slightly acidic conditions, but it breaks down in basic, that is alkaline, conditions, where it turns yellowish-brown and eventually dissolves. The whole logic of fixing follows from this: avoid anything alkaline and lean towards the acidic.
That is why a final, slightly acidic bath helps to anchor the blue. A little white vinegar in the final rinse water, one tablespoon per litre, lowers the pH and stabilises the pigment, which is especially useful where tap water is hard and full of limescale.
Conversely, a perfectly rinsed piece can still fade if it is then washed with an alkaline product, because fixing is not only a matter of rinsing but of the textile's whole life afterwards.
The first wash
The first wash often decides the fate of the piece, and it is best done by hand, in cold water, once the print is completely dry and oxidised. Wait at least twenty-four hours after rinsing so that the blue has reached its stable density, then wash the piece on its own, without mixing it with textiles that could pick up a tint from the slight excess that remains.
For this first wash, rule out any ordinary laundry detergent, which is too alkaline for Prussian blue, and if cleaning is needed, use barely soapy water with a neutral or acidic soap before rinsing in clean water.
On a garment that is worn, such as a cyanotype-printed t-shirt, turn the piece inside out to wash it, so the blue is protected from rubbing. A slight loss of blue is normal at this stage, as it is the unfixed residue coming away; what should worry you is a loss of colour that continues over the following washes.
Ease the textile through its first wash without wringing it or rubbing the design.
Which detergents to avoid on a cyanotype
The most important point for the life of a piece comes down to one rule: avoid alkaline detergents and phosphates. Most commercial laundry detergents are alkaline so that they lift grease better, and many, especially washing powders, contain phosphates or carbonates that raise the pH and gradually dissolve Prussian blue.
Also rule out bleaching agents and household bleach, which destroy the pigment outright, as well as percarbonate detergents and Marseille soap, which are alkaline too.
On the other hand, a mild, neutral soap, used by hand and in cold water, preserves the blue, and a well-fixed textile cyanotype lasts for years, because it is repeated harsh washing that fades it, not normal use of the piece.
Caring for a piece over the long term
Beyond washing, dry pieces in the shade, as prolonged full sun tires the colours, and iron on the reverse at a moderate temperature if needed, since Prussian blue does not cope well with heat combined with moisture. The pigment remains one of the most resistant in the process, and above all you protect it from the two things that really attack it, alkalinity and strong oxidising agents.
Everything starts with good sensitising and the right exposure; without them, no amount of fixing will rescue a blue that was too weak to begin with.
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.