Brian Young tells the fascinating story of salt prints and cyanotypes – photographic printing processes from the 19th Century.
With numerous websites, workshops and exhibitions inviting us to enjoy alternative prints and learn how to make them, non-digital photographic processes, such as salt prints, cyanotypes, van Dyke, albumen and platinum/palladium prints are claiming an increasing number of followers. A combination of science, intuition and lucky accidents, many of these processes have been around for over 170 years and the stories behind them read like an adventure.
Why am I interested in printing without an inkjet? Because it is satisfying to do everything from beginning to end, choose and prepare your own paper and produce final prints of richly toned monochromes. I like their timeless and dreamy look and the way different techniques, the personal touch and different papers create an infinity of unique works.
Are they outdated? I don’t think so and it’s interesting to see how they attract digitally fatigued young people, who invariably ask, ‘Please make me a print’.
There have been numerous arguments about “nostalgic and sentimental” alternative prints, whether they compete with digital and automatically position themselves as more “artistic”. Mike Ware’s essay, In Defence of Alternative Processes (www.mikeware.co.uk) overviews this debate. They are simply there as another expression of an image. Labour intensive and linked to a laboratory setting, old prints are unlikely become mainstream. I simply aim to make people mindful of their existence and their captivating history.
Since the early years of the 19th Century the development of the camera has proceeded alongside the understanding of how certain materials react to light and how they can be used to capture and retain an image.
As the title suggests, this article is concerned with the second partner in this joint venture: the photochemistry of early processes and how they matured up to the beginning of the 20th Century. Apart from interesting you in the history, I hope that you may be inspired to try some of these methods yourself.
The good news is that you don’t need to have studied chemistry to understand how these processes work or even how to carry them out. You will find plenty of help with the practical aspects of old print-making given at the end of the article.
The foundations of mainstream photographic printing were established in the 1790s by Thomas Wedgwood, the son of Josiah Wedgwood, the potter.
Thomas was a sickly and sensitive young man. He devoted most of his short life to studies in education and experimentation with light-sensitive materials. It was this latter work which has led some writers to refer to him as the ‘first photographer’.
In a paper published in 1802, Wedgwood (together with Humphrey Davy) described photograms made on white leather impregnated with silver nitrate. Unfortunately, he did not know how to make these images permanent. Nevertheless, this is the first record we have of silver salts being used in the production of photographic images.
Some thirty years later, in 1833, a certain William Henry Fox Talbot of Lacock Abbey in Wiltshire, went to Lake Como with his new wife Constance. In those days, travellers were expected to return home with pictures of their trip in the form of pretty watercolours and pencil sketches. Fortunately for photography, here was gentleman of private means who could not draw.
This was something of an embarrassment, as men of Talbot’s class were expected to be to be accomplished in the gentle arts. Poor Henry was so hopeless that even with a camera lucida (an optical device which superimposed a scene on the drawing paper) he couldn’t get a decent image.
When he returned from his honeymoon, Talbot began to try out a few ideas that had occurred to him whilst in Italy. He found that a sheet of paper soaked in a weak solution of table salt (sodium chloride) and subsequently coated in silver nitrate, darkened when exposed to sunlight. He also found that after exposure, the application of a solution of sodium chloride or potassium iodide inhibited further darkening. These were two very important discoveries.
First, he had hit on the idea of impregnating a sheet of paper with silver chloride alone. Yes, I know that doesn’t sound particularly inspired but this was such a decisive moment for photography that I can’t resist telling you about it – please stay with me!
If you mix a sodium chloride solution with a silver nitrate solution in a glass it will immediately turn white – the water into milk trick. A chemical switch has taken place, the sodium chloride (table salt) has become insoluble white silver chloride and the silver nitrate has changed to colourless, water-soluble sodium nitrate.
If you try to soak a sheet of paper with a suspension of silver chloride in water, it won’t work. As soon as the paper dries, the silver chloride falls off. That’s why Talbot’s conjuring trick was so clever – he made the chemical switch take place inside the paper.
The other discovery, finding a way to slow down the fading of the image, was the first step towards the concept of fixing – more about this later.
Talbot used his treated papers to make photograms of leaves, grasses and flowers which he could then trace. He called this “the art of photogenic drawing”.
During the following summer of 1835, Talbot took advantage of the glorious weather and went a step further. He had his carpenter make several small boxes fitted with a single lens. At the focal plane, he placed a piece of his sensitised paper. The boxes (or ‘mousetraps’ as Constance called them) were arranged at appropriate spots in the grounds of Lacock Abbey.
Even with the brilliant light of that legendary summer, the exposures were long but eventually Talbot had a set of the first paper negatives ever made; they were crude and unfixed but it was a beginning.
By the end of 1835, Henry Talbot had become involved with other activities and had set aside his photographic studies. It must have been quite a shock when, in January 1839, he heard the news that Daguerre had ‘invented’ photography. Not realizing that the two processes were quite different, Talbot reacted quickly and immediately claimed his prior discovery. He followed this up with the presentation of a paper at the Royal Society describing his photogenic drawings. At this point in the story, the most brilliant mind of his generation, Sir John Herschel, enters the picture. Herschel was a polymath, not only graduating from Cambridge in 1813 as a Senior Wrangler (the top mathematics undergraduate) but doing ground-breaking work in photochemistry as early as 1819 – which he couldn’t be bothered to publish.
Herschel and Talbot were good friends. Shortly after the Daguerre announcement Talbot visited Herschel at his home in Slough. Herschel’s wife wrote at the time:
“I happen to remember well the visit to Slough of Mr Fox Talbot, who came to show Herschel his beautiful little pictures of Ferns and Laces taken by his new process. – when something was said about the difficulty of fixing the pictures, Herschel said “Let me have this one for a few minutes” and after a short time he returned and gave the picture to Mr Fox Talbot saying “I think you’ll find that fixed” – this was the beginning of hyposulphite of soda fixing.”
Because of his earlier studies, Herschel probably knew more about photography than anyone but he didn’t think that his work was sufficiently important to publish. He was the first to use the word ‘photography’ and the terms ‘negative’ and ‘positive’. One cannot help but wonder if the progress of photography would have been better served if Herschel had not, unlike Talbot, been such a highly accomplished artist.
When Henry Talbot returned from Slough, he began to look for ways to improve on his paper negatives of 1835. One of the drawbacks of these negatives from a commercial point of view were the very long exposures needed, even in bright sunlight.
Some great discoveries come about purely by accident, at least that’s how the story goes. One day, in the autumn of 1840, Talbot was working in his laboratory re-sensitising old sheets of treated paper that had been exposed but, for some reason, were blank. Whilst coating a sheet with silver nitrate solution he inadvertently flooded the paper with a solution of gallic acid.
To his great surprise an image appeared, an image resulting from what must have been a few seconds of exposure which had been hidden in the paper until revealed by happy accident. The notion of the chemical development of a latent image had been discovered.
Henry realised that here was the answer he had been looking for. A paper negative that could be exposed for a relatively short time, developed to reveal the image and subsequently used to print a positive image on another sheet of his treated paper. The salt print had arrived.
Talbot called his invention a calotype and, after tweaking it a little by coating the negative with wax to make it translucent, patented the idea in 1841.
Meanwhile, Sir John Herschel was busily inventing the cyanotype. Unlike Talbot’s process which used silver salts, the cyanotype made use of the photosensitive properties of two iron salts, ferric ammonium citrate and potassium ferricyanide.
By 1842, Herschel had perfected the cyanotype process and has historically been given full credit for its discovery. However, recognition must also be granted to Alfred Smee, the young doctor and electro-chemist who supplied Herschel with pure potassium ferricyanide (a safe, very distant relative of the potassium cyanide beloved of crime writers) and the suggestion that Herschel should experiment with ferric ammonium citrate, a substance then used medically as an iron tonic.
The cyanotype is probably best known as a means of reproducing architectural and engineering drawings in the form of blueprints. The process was also applied by Anna Atkins, a botanist who published photograms in her 1843 book “Photographs of British Algae – Cyanotype Impressions”. Perhaps the most curious application of the cyanotype was its use in printing postage stamps and currency during the Boer War.
Given a good quality negative, the cyanotype and the salt print methods can be used to make wonderfully rich contact prints in blues, blacks and sepias. The section at the end of the article will tell you all you need to know to do this.
By the 1850s, photography had become the new craze and went commercial. Everybody wanted to have their picture taken and the process used was the albumen print.
The disadvantage of the salt print was its dull appearance. Although the internal chemistry of the albumen print was identical to that of the salt print, the addition of albumen (egg white) to the paper surface was a distinct improvement.
It produced an attractive glossy finish which brought out the detail of the image and enhanced the colour. If a matt finish was preferred then a little arrowroot could be added to the mix. The coating tended to crack over time and this was prevented by the addition of honey.
The production of salted albumen coated papers for subsequent sensitising with silver nitrate was big business during the second half of the 19th Century. It is said that, at one time, the Dresden Albumizing Company was using over 25 million eggs a year. Recipes requiring egg yolks abounded.
When you have mastered the art of the salt print, you might wish to try albumen printing. It is a long and pains-taking process but everything extra you need is available in the kitchen. Alternatively, you could just take the easy route and liven up your salt prints and cyanotypes with a coat of thinned artist’s varnish.
The calotype paper negative was gone by the end of the 1850s and albumen prints would have been printed from Fred Archer’s glass wet plate negatives until the 1880s when the dry plate was introduced. Gelatin silver prints took over from the mid-1890s and are still used today.
Although the first reference to a photographic enlarger was made by Draper in 1840, they were not commercially available until the turn of the century. In the absence of an enlarger, contact printing was used. If you wanted a big image then you needed a big negative and a big camera.
Large format cameras were the norm and plates up to 8in x 10in were common: plates as large as 20in x 24in (and the cameras to take them) were not unknown. Large plate cameras may have been inconvenient to handle but the image resolution was superb.
Towards the end of the century another of Sir John Henschel’s discoveries from 1842 gained recognition. This was the argentotype which used a combination of iron and silver salts. They became known as van Dyke prints because the colour was reminiscent of the work of the Flemish painter. It is relatively easy to make but mixing the sensitizer needs care. The final result is very similar to a salt or albumen print but more brown than sepia.
The platinum print (and its less expensive cousin, the palladium print) became popular when William Wallis introduced platinum paper in the mid-1870s. Difficult and expensive to make but with enduring and resonant tones, these are the king and queen of old processes. Platinum printing had a revival in the 1960s with photographers and printers such as Robert Mapplethorpe, Richard Arentz and Irving Penn.
I hope that you have enjoyed this brief introduction to the history of printing. There is so much more to know and a very helpful book is Spirits of Salts by Randall Webb and Martin Reed, published by Argentum. The book is available from Silverprint Ltd (www.silverprint.co.uk/) as are all the chemicals which have been mentioned in this article.
If you are interested in learning about the more exotic methods and printing as art, I strongly recommend Christopher James’ The Book of Alternative Photographic Processes published by Delmar in the United States.
Just a word about safety: since you will be handling chemicals, please consult Ilford’s Health and Safety pages (www.ilford photo.com) before you get going.
Good luck with your printing, I trust that in realising these old processes you have as much enjoyment as I have over the past few years.
You will need a few items of equipment: 100 and 250ml plastic measuring cylinders; digital scales capable of weighing to 0.1g; a 60cm steel rule; several brown glass bottles in 250ml and 1litre sizes; a small plastic funnel; two or three 14x18ins plastic darkroom developing trays; flat brushes from an art materials shop, one for each process; several small pots or jam jars; a seconds timer; nitrile or latex protective gloves; safety goggles; and an apron or lab coat.
Making a negative
Salt prints and cyanotypes are contact printing processes, so the final image is the same size as the negative. In practice, image size is limited only by the size of transparency available and the capacity of your printer.
The more contrast in the original image, the better the final print. This is particularly true for salt prints. Contrast can be increased in Photoshop using Curves or one of the Artistic Filters. Posterizing also works well.
You will be starting with a digital image in RGB mode, and following a workflow created by Christopher James (“The Book of Alternative Photographic Processes”). The first task is to desaturate and adjust the contrast. When you are happy with this, go to Image-Adjustments-Invert to create a black and white negative. You could stop at this point but since you will be printing under UV light, an orange and black negative gives better contrast. Go to Layer-New Fill Layer-Solid Colour, ensure that Opacity is at 100%, and select Mode-Colour.
Press OK and in the Colour Picker Window, set CYMK to 0, 55, 55, 0 respectively, to produce a deep orange. Next, go to Image-Rotate Canvas-Flip Canvas Horizontal: this step will allow the ink side of the printed negative to be in contact with the paper. Finally, flatten the image and adjust the size. Print the negative on an A4 transparency.
The UV source
The sun is the ultimate UV supplier, but since we see so little of it in Northern Europe, an artificial source is essential. My recommendation is a 300W Osram Ultra-Vitalux lamp. Because of the intense heat generated by this bulb, it must be fitted in a ceramic holder. There are UV safety notes on the Osram website (www.osram.com/uv-ir).
My lamp is surrounded by a fibre board box, with both top and bottom open. The assembly is attached to the wall of the workspace so that the UV light is concentrated in an area immediately below the lamp. Ensure that no light could be inadvertently directed into the eyes of the operator or of anyone else in the vicinity.
Build a shelf under the lamp to support the 30x42cm printing frame. Ideally, the height of the shelf should be adjustable to 20, 30 and 40cm below the bulb.
Choosing and preparing the paper
Paper for alternative printing must be strong enough to withstand repeated washings, so look for a weight in excess of about 250g/m2. A good art store will have plenty of suitable papers in stock. In general, I use French-made Lana Acrylic, with a weight of 360g/m2. The paper is a joy to use, and has a size of 50x65cm, which allows for two A3 (30x42cm) sheets: off-cuts can be used for exposure test strips. Rather than cutting the paper, tear it against a steel rule to obtain an artistic deckle-type edge. For toned cyanotypes you may prefer the more expensive 300g/m2 Hahnemühle matt watercolour board since borders tend not to stain.
Paper for salt prints must be soaked in a 2% solution of common salt (20g salt in 1 litre of tap water) before being sensitised.
Some papers may have been sized during manufacture to make them less porous and some may not. It is safest to assume that your paper has not been sized and to do it yourself.
Salting and sizing may be combined in one operation (note that although paper for cyanotypes does not need to be salted, it does it no harm).
Here is how to salt and size: buy some transparent leaf gelatin from the supermarket. In a beaker, soak 2g of the gelatin in 100ml of cold water for about 15 minutes, then top up to 250ml with hot water from the tap. At this point, you can add 5g of salt if required. Stand on a warm radiator and stir occasionally until all the gelatin is dissolved. Allow to cool.
Treat the paper by brushing the salt and gelatin mixture onto the area to be occupied by your negative, and hang up to dry.
The printing frame
The printing frame is very simple to make. It consists of a 30x42cm fibre board back and a piece of picture glass of the same dimensions. The sensitised paper and negative are sandwiched between the backboard and glass. For aesthetic reasons, try and arrange the A4 negative symmetrically on the A3 paper.
Ensure that the negative is the right way around and that the inked side is in contact with the paper. If you have carried out the creation of the negative correctly, then these two conditions should be met automatically. Close the periphery of the sandwich with eight strong spring clips. To protect the glass from the clips, make a frame of thick card about 25mm wide to go around the edges.
The assembly is now ready to be exposed under the UV lamp.
Making a cyanotype
The two cyanotype solutions are made up as follows:
- dissolve 20g of green (not brown) ferric ammonium citrate in 100ml of tap water. Store in a brown glass bottle.
- dissolve 8g of potassium ferricyanide in 100ml of tap water. Store in another brown glass bottle.
On a sheet of prepared paper and using a soft pencil, mark where the corners of the negative will go. Take 15ml of each solution and mix them together in a small jar. In subdued light, brush the mixture onto the paper in the area outlined. Don’t flood the surface but be sure to cover every spot. It doesn’t matter if you go over the edge – brush strokes outside the image just add to the charm of a cyanotype. Finish by carefully laying off both horizontally and vertically.
Allow the paper to dry by itself in the dark for a few hours before using.
Mount the paper and negative in the printing frame (ink side of the negative in contact with the sensitised side of the paper) and place under the UV lamp. With the shelf set at 40cm below the lamp, exposure should be about 10-12 mins (less at shorter distances). However, with each new negative, it is wise to prepare and expose a few test strips before making the final print.
Put the exposed print in a large developing tray and wash it thoroughly for two or three minutes in the bath or shower with cold water from the hand spray.
The print will be a bright blue, which will darken slightly over the next few days. Lay flat to dry if you are intending to tone otherwise a stain may show up in the borders.
Toning a cyanotype
If you don’t care for bright blue, the colour of a cyanotype can be toned down to a rich black with strong coffee. Add 1 litre of boiling water to 20g of instant coffee. Cool it and bottle. Next prepare a weak solution of bleach by dissolving a pinch of sodium carbonate (washing soda) in 1 litre of water.
For the best results, let the print age for a few days, then start the toning process by giving it a 5 minute warm water bath in a developing tray. In another tray, prepare the bleach solution. Transfer the print to the bleach for no more than 30s and then put it back in the water bath and wash thoroughly.
Pour the coffee toner into a third tray and leave the print to soak face down for about 30 minutes. Wash well and dry flat.
For a sepia tone try strong green or black tea but use a slightly stronger bleach consisting of one quarter of a teaspoon of sodium carbonate in 1 litre of water.
Making a salt print
There is one salt print solution which is made up as follows:
- dissolve 12g of silver nitrate in 50ml of distilled water;
- dissolve 6g of citric acid in 50ml of distilled water.
Mix the two solutions together and store in a brown glass bottle. The citric acid acts solely as a preservative and has no role in the photochemistry.
From this point, everything that has been said about the cyanotype process applies to salt printing, with two exceptions. First, the exposure will be much shorter than that for a cyanotype – typically only 3 mins at 40cm. Secondly, after an initial five minute wash, the print must be fixed. This is done in a bath made by dissolving 25g of sodium thiosulphate powder and 2g of sodium carbonate in 500ml of cold tap water.
Leave the print in the fixing bath for about five minutes, agitating gently from time to time. Pour the fixer into a bottle for further use, and wash the print for another 30 minutes with water or use a ‘hypo’ clearing agent. Hang up to dry.
After the first wash, the print is brownish-purple, but on fixing it turns an unattractive light brown. Fortunately, in time, the colour mellows to a dignified greyish-sepia.
Blueprint to cyanotypes – Exploring a historical alternative photographic process
by Malin Fabbri and Gary Fabbri
A well illustrated step-by-step guide to cyanotypes.
A lot more information on the process, chemicals, coating, exposure, printing, making negatives, washing and troubleshooting is available in this book.
Strongly recommended for beginners