A pinch of salt and a couple of pixels

Reporting on a fun and informative workshop to learn contemporary salt printing.

Contemporary salt printing workshop

One of the earliest photographic printing techniques is that of the salt print, a hand-coated two-step process. A salt solution is applied to the paper, allowed to dry then followed by an application of silver nitrate solution to form light sensitive silver chloride. When exposed to light the silver chloride is changed to image making metallic silver.

As metallic silver forms on the paper it has a masking effect which allows more time for development of the highlights and thus creates a greater tonal range than is found in other photographic print processes. This presents the photographer with the challenge of producing negatives capable of utilising the potential of the process. Furthermore the colour, tones and hues of the print can also be affected by variations in the chemistry and application of each solution.

These were the attributes of salt printing that first attracted me to the process some two and a half years ago when I attended a workshop introducing alternative photographic techniques. Although that workshop focussed mainly on cyanotype and Van Dyke brown printing, other processess were introduced and of these, salt printing was what caught my attention. It’s been a while and is about time that I followed up on my interest!

So it was that last weekend I joined a Contemporary Salt Printing workshop at Stills Gallery in Edinburgh, led by tutor Brittonie Fletcher. Stills has well equipped darkrooms and comprehensive digital editing facilities and Brittonie is Media Instructor at the Royal College of Art in London so my expectations were high. Also, Brittonie had been the tutor on that first workshop that so whetted my appetite.

The contemporary element of this workshop was the application of digital technologies to optimise the negative for the traditional process. Regardless of the source image and without altering the print making process, we would use digital editing tools to produce negatives on acetate sheet from which we would make our salt prints. As with any workshop, the purpose was to learn and understand the process. Any outstanding work will only be the result of application and practice in the weeks and months ahead!

Each of what turned out to be four attendees were asked to bring two or more digital image files, negatives or other media to work with. I took a selection of files, sheet film negatives and glass plates. The plates caused some excitement and we used one to make a comparison of a salt print made straight from the plate and another from an optimised digital negative produced from a high resolution scan of the plate.

Day 1

After introductions and a brief history of salt printing we got down to the business of preparing solutions, cutting paper and setting out the darkroom.

We prepared a 2% salt solution for sizing our paper, a 3% salt solution for the salt rinse bath and a bath of 10% hypo fixer. Finally we very carefully measured out silver nitrate (costly stuff!) to mix a 12% solution. These were the concentrations we would use for the workshop, however we were instructed that by varying them we could alter the final tonality, contrast and range of our prints.

Sheets of Fabriano 5 art paper were cut down to the size we would be printing. Notes about solution strengths and sizing times were made in pencil on the back of the paper before each piece was soaked in the salt sizing solution for three to five minutes and then hung up to dry.

While waiting for the paper to dry, we took our chosen images to the digital lab where Brittonie prepared digital negatives on Permajet acetate sheets from which we would make our first prints. The detail of preparing the digital negatives would be explained on Day 2 but for today the same actions were applied to each image file.

Back in the darkroom we sensitised our now dry, sized paper. A pipette was used to apply a few drops of silver nitrate solution onto the paper which was quickly spread by means of  Hake brushes or foam brushes. I chose to use a Hake brush, spreading the silver nitrate not quite to the paper’s edges so as to leave the brush marks at the edges. Others used foam brushes and applied to the edges or used masking tape for a clean line on the paper.

Our first step was to make a test strip. This would establish the required exposure to achieve maximum density and we determined a starting point for our prints to be eight minutes in Stills’ UV light box. Denser negatives might need a little more, thinner ones a little less. Salt printing is a printing out process and so the developing image can be examined as exposure progresses, subject to the negative and paper remaining in register.

Following exposure the prints were placed in the salt rinse bath for five minutes, followed by a short rinse in clean water before fixing in the hypo solution for about a minute. Finally the prints were washed in fresh water for a minimum of thirty minutes before being gently squeegeed and laid out to dry overnight.

First digital image file, Day 1
Second digital image file, Day 1

Day 2

The day commenced with a review of the prints that had been left to dry overnight. We made comparisons between coating techniques, amount of silver nitrate used, length of time the paper was soaked in salt solution and timings of the salt rinse and fix. It was very clear that each print was the crafted product of its printer, showing individual touches and the nuances that could be achieved with very minor variations in process.

But today was to be all about the ‘Contemporary’ part of the workshop title. We would spend much of our time in the digital lab learning how to optimise each image file and create our own digital negatives to print from. Files would be resized, a curve would be applied and a colour screen determined to produce maximum highlight detail. We used Photoshop CS6 and although I have had little experience of the program I was able to follow what we were doing and am comfortable that I can apply the knowledge with the editing tools that I use.

The glass plate image that I printed on Day 1 as a straight contact print from the plate rather than from a digital negative, has some fine detail in the shadow areas that didn’t show up well in the print. Today would be an opportunity to find whether that detail could be brought out in a print from a digital negative created from a high resolution scan of the plate.

With our digital negatives prepared and printed on Permajet acetate sheet, we returned to the comforting gentle red glow of the darkroom to complete the printing process by contact printing and processing as we had learned on Day 1.

Glass plate with hand-poured SE1 emulsion, Days 1&2

Conclusion

That was fun! And if fun wasn’t enough I learnt stuff that I can do and develop in my own style and time.

The printing process is really very straightforward and one that I can see being quite possible to accomplish in my ‘ensuite’ darkroom at home. Other than a UV light box, I already have all the equipment I might need.

Silver nitrate is the main expense and if I want to include a digital negative stage, Permajet acetate sheets are quite a bit more expensive than regular acetate sheets (which just don’t work). UV face tanning machines are readily and cheaply available and are easily adapted to small-scale use. Alternatively I could ‘go native’ and use a vintage printing frame in the elusive Scottish sunlight – there’s no reason not to at least give it a try!

Finally, I can’t close this without a little praise for both the tutor and the facility. Brittonie is a wonderful instructor, so generous with her time, knowledge and skills and is genuinely interested in her pupils’ work and development. Stills, as I have already indicated is comprehensively equipped to support photography practice of all styles, from historic processes through darkroom to digital and video editing suites with training facilities to match.

Senior Moments

I took a Trip to Falkirk for an Intrepid photo-outing. But not all went to plan …

The idea was to take The Intrepid and a half a dozen sheets of Harman Direct Positive paper for a walk around The Falkirk Wheel, a unique boat lift between the Union Canal and the Forth and Clyde Canal in central Scotland, and then on for a visit to the nearby site of the Antonine Wall and Rough Castle Roman Fort. For a few snapshots along the way I took my Olympus Trip loaded with Kentmere 100 film.

Two cameras, one to be set up on a tripod after careful consideration of the viewpoint then focused, loaded, light measured for calculation of shutter speed and aperture before the exposure could be made. The other in a pocket to be taken out, pointed at the subject and the shutter pressed to take the shot without delay.

Nobody takes a blind bit of notice to the Olympus Trip whereas The Intrepid attracts all manner of attention. People stop to look. They ask questions. They tell of their forebears using cameras like these. Their children have to see what’s going on below the dark cloth and their dogs are attracted to the legs of the tripod!

All of that attention when trying to concentrate on the process of taking a photograph with The Intrepid can lead to confusion for the old codger that I am! I made a complete mess of exposure meter readings and camera settings. Of my six sheets of paper only one came out as I had intended, one of two barges passing each other on the Union Canal above the Wheel.

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The remaining five were all either very under- or very over- exposed. However, one of these, of the entrance to Rough Castle Tunnel, although about three stops overexposed has been growing on me so I count it amongst the ‘keepers’.

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So there it is. Memories of a day out, exposures made, lessons learned and the sense of satisfaction from crafting the images back in the darkroom.

Taking a squint at George

Continuing the stereo pair experiment – could I make it work with a large format camera, using consecutive rather than simultaneous exposures?

Having made a reasonably successful attempt at stereo pair photography with a pinhole camera I felt encouraged to explore whether the 3-D effect could be achieved using the movements of a large format field camera.

My theory was that a stereo pair from a single camera could be achieved by making consecutive exposures using horizontal shift of the front standard to effectively view the subject from two adjacent points.

To test my theory I set up ‘George’, an almost life-size polystyrene head, at a metre or so from my Intrepid camera. Then I made two exposures, the first with the front standard set about 15mm left of centre and the second with it set about 15mm right of centre.

The total separation of 30mm ensured that the image circle of the offset lens would cover the film and also that at at such a subject distance, the whole of George’s head would be included in each image. The Intrepid camera allows for a maximum of about 65mm total horizontal shift so there is scope to increase the separation as long as the image circle projected by the lens allows it without vignetting. I would expect that to achieve a realistic stereo effect the ideal separation should match the average distance between the eyes which in an adult is about 64mm.

I scanned the negatives side-by-side to produce a stereo pair (as at the top of this post). I’ve since re-scanned the two images and created a print with each separated by 30mm just as they were taken. Take a squint at George to overlap the two images as a third virtual 3-D image in the centre:

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So far, so good, although I’m not totally convinced of the stereo effect with George alone. The next step would be to test my theory ‘in the field’ with near, mid and far distant subject elements. Decent weather would help too!

After a series of depressingly dreich grey weekends, my travels in search of weekend light and suitable subject matter for the task took me to the Southern Uplands and the villages of Wanlockhead and Leadhills. There I found the remains of some old buildings in a quarry beside the old narrow guage railway that once served the lead mines here and now transports tourists, in season, between the two villages. The location served my purpose and being out of season, was free of tourists! I took two sets of three images: one with the front standard moved fuly to the left, a centred exposure (which I used to frame and focus the scene), and a third with the standard fully to the right. The total separation between left and right was 65mm but of course each individual image of the set was just 32.5mm.

Here are the sets of images, each followed by a print of left and right separated by 65mm which should be viewed by squinting at the pair to create an overlapping central virtual image:

(looking north-east)

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(looking south-west)

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Do they work? – I’m not sure. The second set are probably a better subject with the metal bars sticking out of the wall and the telegraph poles giving obvious ‘depth points’. If I concentrate my focus on the central part of the merged virtual image I can see the 3-D effect but overall it does appear confused. Choosing any combination of two adjoining photos, i.e. that have been taken with only 32.5mm separation seems to work better. So much for my theory  of matching lens and eye separation!

The sun was setting over the hills to the west and the light was beginning to change quite quickly. This may be adding to the confusion as the shadows cast by the sun have moved between exposures (as have the clouds). This would not have been a problem had I been making the exposures simultaneously.

I had intended a third set which I’d like to think would have been best of the lot but by this time the light was changing so fast I realised that because of the rapidly lengthening shadows, consecutive exposures would not work. I made do with just one image.

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All of the photos here are straight, unaltered scans of the negatives. I’m quite sure they will all print better than reproduced here so whatever I might conclude about the success of the stereoscopic experiment, I still have printable, interesting negatives to play with in the future.

The stereoscopic experiment has been interesting. I have no doubt there is a relationship between lens separation, focal length and main subject distance. The mechanism for viewing is also important, my squinting to create a virtual third image being the most basic, and I imagine needs ideally to be matched to the geometry of the taking equipment. My best success was undoubtedly with my stereo pinhole camera, the size and geometry of which would match the Victorian stereographic viewers available on auction sites.