A pale cyanotype almost always comes from underexposure, with too little iron having reacted in the sun, whereas a print that washes out in the water points instead to a rinse that was too vigorous or too warm, or to unsuitable paper.
A cyanotype that comes out pale, fades in the water or ends up stained is always disappointing, especially since the process looks simple and you were expecting the deep blue the chemistry promises. In workshops, it becomes clear that almost all these failures come down to two or three recurring causes, and that a specific symptom usually points to a specific cause, and therefore to a clear correction.
The most practical approach is to start from what you see on the print and work back to what caused it. This page sticks to identifying the problem, with the detailed steps covered elsewhere, because the way to rinse a cyanotype and the way to expose it in the sun each deserve their own treatment. To place each step within the process as a whole, the cyanotype guide is the place to start.
A cyanotype that is too pale after rinsing
This is the most common failure of all. The print looked distinctly blue when it came out of the sun, then lost its colour in the water and ends up a dull blue with no density, sometimes almost grey. In the vast majority of cases, the cause is underexposure: too little UV reached the paper and too little iron reacted to form Prussian blue.
The trap lies in the misleading colour of the damp paper. Freshly exposed, the coating already shows a blue-grey that gives the impression of a finished print, whereas the rinse is going to carry away all the unreacted iron and reveal the true level of blue, which is always lighter than what you saw in the sun. A print that looks perfect on the exposure table is almost always underexposed.
Expose for longer
The correction is to expose for longer and, above all, to rely on the colour change on the surface rather than on the clock. The most brightly lit areas should shift to a bronzed grey that is distinctly darker than the final blue you expect, which seems counter-intuitive but remains the most reliable guide. Allow anything from a few minutes in full summer sun to several tens of minutes in overcast weather or in winter, and keep going as long as the bronze shift is not clear.
Two secondary causes produce the same symptom. A solution that is too dilute or a poorly coated paper lays down too few salts in the first place, and paper that was sensitised a long time ago loses some of its sensitivity, which lengthens the exposure time needed. If you expose for long enough and the blue stays pale, look at the solution strength and how fresh the paper is.
Looking at the paleness, the washed-out areas and the unevenness helps you describe a test print before looking for its cause.
A cyanotype that fades or washes out in the water
This symptom looks like the previous one but has a different origin. Here the blue does not lack density to begin with: it goes into the water, the rinse water turns blue and the colour leaves with it, leaving a weakened print, or even areas that are almost erased. The problem then lies in the washing and everything around it.
The most common cause is a rinse that is too vigorous or too warm. A direct jet, lukewarm water or energetic agitation tears away Prussian blue that is not yet firmly attached to the fibre, especially in the first few seconds. Rinse in cold water, under a gentle trickle or in successive baths, without rubbing, until the water stops taking on colour.
The paper may also be to blame
Unsuitable paper produces the same effect. A surface that is too smooth, coated or poorly absorbent holds the salts badly: they stay on the surface and come away in the wash. A watercolour paper of good weight anchors the pigment in the fibre and stands up to rinsing, whereas printer paper washes out almost entirely.
Gradual washing out on fabric is a special case, because textile needs its own fixing to withstand repeated washing.
It is a subject in its own right, separate from rinsing a paper print, and it is covered in the page on how to fix cyanotype on fabric without it washing out. On fabric, the pattern disappears in the wash mainly when the initial rinse was cut short or when an alkaline detergent attacks the Prussian blue.
Stains and tide marks on the print
Irregular marks that are not part of the image almost always betray a problem that arose before exposure, at the coating or drying stage. The blue merely reveals a defect already written into the sensitive layer.
Tide marks, those darker, wave-shaped edges, come from paper that was poorly dried or laid flat to dry without care, with the solution migrating towards the areas that are still damp and becoming concentrated there. Dry the coated paper perfectly flat, away from light, until it is completely dry to the touch before laying the negative on it.
Spots and fingermarks
Isolated lighter or darker spots often come from uneven coating, a brush overloaded in places, a drop that fell on the layer, or fingers that touched the sensitive surface and left a deposit on it. Handle sensitised paper by the edges and spread the solution in an even layer, crossing your strokes.
White dots in a blue area generally indicate dust or a bubble caught between the negative and the paper during exposure, which blocked the UV at that spot. A negative pressed flat under clean glass, on a dust-free surface, gets rid of this defect.
A blue haze over the whites
When the areas meant to stay white take on a bluish haze and the image loses its contrast, the paper has received UV where it should not have, before or during exposure. The white of a cyanotype is the white of the bare paper, and any iron that has reacted in these areas tints it permanently.
The cause most often lies in handling in the light. Sensitising or drying the paper too close to a window, leaving it lying around in daylight before exposing it, or using paper already partly fogged by poor storage is enough to muddy the whites. Work in the subdued light of a room, away from direct sun, and keep sensitive paper in an opaque sleeve.
A negative or object that is not pressed flat also lets UV leak in at the edges of the protected areas, which thickens the outlines and greys the neighbouring whites.
The contact must be firm and flat across the whole surface, with the negative pressed under glass or in a printing frame, so that the boundary between exposed and protected stays sharp. A blurred print likewise betrays poor contact, whether from a negative that was not pressed flat or from paper still damp enough to stick to the negative.
A dull or yellow-stained blue
A blue that lacks brilliance, looks dull or keeps yellow-green traces after drying usually signals an incomplete rinse.
The unreacted iron has not been fully removed and remains in the fibre, where it dulls the blue and can go on degrading it over time, which is why a rinse carried through to the end also determines how well the print keeps over the long term.
In that case, extend the rinse until the water is perfectly clear and the unexposed areas have turned white again, with no yellowish residue. A well-washed print, dried in the shade, also darkens naturally over the following hours as it oxidises in the air, which gives it more depth. This oxidation and the ways to speed it up are covered in the page on how to intensify a cyanotype.
If the blue stays dull despite a complete rinse, the paper is often to blame: a paper that is too acidic or too heavily loaded with coating agents hinders the formation and stability of Prussian blue. Going back to a neutral watercolour paper of good weight solves most of these cases.
Reading a failure to improve
Every failed cyanotype carries within it the clue to its cause, and learning to read it is better than piling up tests blindly. A pale print after rinsing points to the exposure, a print that washes out points to the rinse and the paper, stains and tide marks point to the coating and drying, and a haze points to stray light.
The opposite defect, a print that is too dense with blocked-up shadows, comes from overexposure and can sometimes be partly rescued in an alkaline bath, as explained in the page on how to lighten a cyanotype that is too dark. By isolating one symptom at a time, you quickly work back to the correction.
To rule out paper-related causes from the outset, the Sténoflex cyanotype kit brings together the two iron salts and a watercolour paper suited to the process, so you can focus your diagnosis on technique rather than on materials.
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.