Cyanotype - color it blue

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Author: Louie Powell
Date: June 1991
From: PSA Journal(Vol. 57, Issue 6)
Publisher: Photographic Society of America, Inc.
Document Type: Article
Length: 2,024 words

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In 1839 two events occured which began the era of photography. Daguerre read a paper at the French Academy of Sciences in which he announced a process for producing a permanent positive image on a metal plate--a process which came to be known as the Daguerrotype. The Frenchman claimed he had been using this process for six years.

The same year, an Englishman, Henry Fox Talbot, announced to the Royal Society that he too had developed a process for photography. In this instance, however, the process led to a negative image on a paper substrate. Fox Talbot reported he had four years of experience with his method.

Students of marketing know that just about any publicity is good publicity if it serves to increase public demand for a product. Such was the case in the early days of photography. Daguerre and Fox Talbot's competing claims to be the inventor of photography led to an enormous increase in public interest--even though both methods were slow, messy, impractical and for the Daguerre process, dangerous. As a result, there followed a great deal of research into other ways to make photographs.

In 1843, Sir John Herschell read a paper to the Royal Society in which he discussed two topics:

* First, light will bleach the juices extracted from certain flowers, a process he called Chrysotype or Anthotype.

* Second, when ferric salts are exposed to sunlight, they are reduced to the insoluble ferrous state, a process known as Cyanotype.

Of these two, the Cyanotype process proved to be a very practical method to produce permanent images, while Chrysotype was shown to be completely useless. Cyanotype was a common experimental photographic process through the 1850's, and for a period there were even commercial iron papers. By the mid 1870's, however, the silver process we know today had matured to the point where Cyanotype was no longer used for photographic objectives, but it remained a viable process for reproducing technical drawings until the diazo process became available in the 1950's. Many PSA members who are involved in engineering or architecture will recall wetprocess blueprints which were white images on blue backgrounds.

Cyanotype still lives today. Usually thought of as an experimental, non-silver alternative process, it is also an option to be considered for its creative value when its characteristic blue iron stain color will add to the final image.

How To Get Started:

Cyanotype is a process which can be easily employed today for creative purposes. Darkroom requirements are minimal, but one needs two essential ingredients.


Cyanotype is a slow contact printing process, and as such, requires negatives the size of the final print. For most applications, this means that the original negative must be shot using a large format camera, or else an enlarged negative must be produced. The latter option is the practical choice for most of us.

A number of years ago I acquired a small supply of Kodak 2575 Direct Positive Duplicating Film. This is a continuous tone film of moderately high contrast which can be handled under ordinary safelight and which, when exposed in an enlarger and processed in Dektol, produces a copy negative. That is, a negative can be enlarged in one step to produce a larger negative. All of my experiments with Cyanotype has been using this material, and I recommend it.

An alternative is to enlarge a negative on conventional film. If I were to do this, I would first contact print the original camera negative (35mm or 6x6) to produce a film positive, and then enlarge this to produce a large negative. This would be more economical.

Litho film could be used instead of conventional negative film. Of course, litho film has very high contrast and the resulting prints will contain only the extremes of the tonal scale--bright highlights and deep shadows. However, starting with litho film might make sense for someone who is already experimenting with high contrast images and who wants to try Cyanotype without investing in another special emulsion.

Enlarged negatives can also be created directly from slides. In this case, only one step is required--a contact positive is not needed. However, one must recognize the spectral sensitivity of the film used to make the large negative will respond naturally to the colors in the slide with the result that the tonal range of the final image may be distorted.


The other element is printing paper, and this is strictly do-it-yourself since commercial papers are not available. Home-sensitized paper is often an obstacle in experimental processes, but for Cyanotypes, sensitizing paper is neither hard, messy, nor very dangerous.

I have found that for Cyanotypes, I prefer a paper with a distinct texture. For this reason, I use a fairly heavy "cold press" water color paper which has a rough texture on the felt side. I buy the paper in a nearby hardware/art store in pads of twenty sheets--which works out at about 20 cents a sheet.

Many references on Cyanotype recommend sizing the paper before sensitizing it, and then talk at length about boiling Knox gelatin or Argo starch. The thought of that hassle caused me to try Cyanotypes on unsized paper, and I have found the results to be acceptable. Later I discovered spray starch which does just as good a job as the boiled variety but with much less effort. If you choose to size your paper, this is the way to go.

Sizing does two things for the final image. First, in a sized print the image lies directly on the surface, while in an unsized print, it is embedded in the fibers of the paper. The decision of which is better is purely subjective and may vary from one image to the next. The second advantage of sizing is that because the "emulsion" is on top of the sizing and not in the paper fibers, the unexposed ferric salts in the emulsion can be more easily washed out in processing. As a result, unsized prints require much more washing and even then the highlights may gradually turn a faint blue as the print ages.

Various references give different formulas for the sensitizing solution, which illustrates that the proportions are not critical. One common formula is:

* Solution A--100 ml water and 20 g. Ferric Ammonium Citrate (green, not brown)

* Solution B--100 ml water and 8 g. Potassium Ferricyanide

Store both solutions in tightly stoppered brown glass bottles until needed, and mix 1:1 for use.

I use a variation on this. Many years ago I acquired a number of small, plastic demmitasse spoons which I use for darkroom chemistry. I have a 50ml beaker which I half-fill with warm water. Then I add two spoons-full of the Ferric Ammonium Citrate and one spoonfull of Potassium Ferricyanide. The chemicals are inexpensive enough that if I make more than I need and have to throw it out, there is no real penalty.

The chemicals are very inexpensive and can be purchased through any chemical supply house. Photographer's Formulary sells both bulk chemicals and an economical starter kit.

Once the yellow-green sensitizing solution is mixed, brush it onto the paper. I use a sponge type brush, but a conventional bristle brush may give interesting results if the edges of the sensitized area are left rough. This step can be done under ordinary tungsten light. Let the paper dry--I usually either hang it from hooks using clothespins or lay it out on sheets of newspaper in the darkroom with the light off. Usually half an hour with the basement dehumidifier on is enough to dry the paper. If I am impatient, blowing warm (not hot) air over the paper with an old hair dryer speeds the process.

A common complaint about Cynanotypes is that the blue is too faint. This may be because of the proportions of the chemicals in the sensitizing solution, or it may be the result of using too little solution. I have found that if I recoat the paper a second time after it has first dried, I get a more intense blue image.


The ferric salts in a Cyanotype emulsion are sensitive to ultraviolet light. Some of the options to expose the paper are sun lamps, commercial arc lamps, or black lights, but the simplest answer is the cheapest--use the sun.

Place the paper in a printing frame with the dry yellow sensitized side face up. On top of this place the enlarged negative. Exposure times in direct sunlight vary from 10 to 20 minutes on a bright day depending on the density of the negative and the chemical activity of the emulsion. Recall that this is an experimental process and don't get uptight if your first few efforts are less than successful. A couple of hints on exposures:

* the image will bleach somewhat during processing--so print a bit darker than seems right

* correct exposure will result in the yellow emulsion turning silverish in color, and in some areas it will appear to reverse tonality. That is, what should be a deep shadow will look so silverish in color that it appears more like a highlight.


Processing is simple--just place the print in a tray of water and rinse it for half an hour or so, making sure all the residual yellow sensitizer washes out. The reduced ferric salts will oxidyze to a deep blue. This oxydization process can be enhanced by briefly treating the print in a weak solution of Potassium Dichromate or Hydrogen Peroxide. After all the residual yellow sensitizer has washed out--and that is important because if it is not removed, it will eventually be reduced to the ferrous state and turn blue--dry the print using whatever convenient method you choose.


Like any experimental process, there are a variety of things you can do to produce different results. Some are improvements, and some are not, and only you can tell the difference.

Toning is an option which, according to most references, tends to be less

successful. I have never bothered to even try toning because I find the native blue color enough of a deviation from normal. Bleaching a Cyanotype in ammonia, and then toning in either tannic or gallic acid supposedly will produce purple tones. Treating the print in a warm solution of lead acetate is reported to produce deeper blue tones. There are even formulas for red tones. However, most of the toning formulas are not as permanent as the original iron stain image.

Another option, which I have found to be fun, is to hand color the Cyanotype image using ordinary transparent water colors--I borrow my kid's water color sets for this purpose. I'm not a painter, but the blue image gives me something close to a paint-by-numbers simplicity which even I can cope with. I have found that best results are when either just a little color is added to an otherwise monochromatic image, or when the colors are intentionally made unrealistically intense.

Finally, there is a good news/bad news aspect to Cyanotype. The bad news is the process can stain clothing and one must be careful to use an apron and/or old clothing when working in the process. The good news is that, because it stains clothing, it can be used to print images on clothing. Instead of sensitizing paper, try sensitizing a T-shirt and printing your favorite image on it. Most fabrics work well, but well-washed natural fiber fabrics work best. And, when you complete that T-shirt masterpiece, be careful how you wash it. The image can fade over time, especially if you are heavy-handed with household bleach.

I have had a lot of fun playing with Cyanotype--and have even had a few competition successes. Some subjects react very well to the blue treatment--old buildings, male portraits, and even flowers. It's easy, inexpensive, and most important, different from conventional silver-based monochromatic photography. Like they say at the hamburger shop, sometimes you've got to break the rules.

Louie Powell has been a member of PSA since 1984. A former Area Representative, he lives in Scotia, N.Y. where he is an active member in the Schenectady Photographic Society.

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Gale Document Number: GALE|A10888373