Work in progress

The ongoing saga of my salt print experiments.

To date I’ve made a couple of attempts at salt printing: at a workshop back in April which I followed up last month with my first attempt at home. Feedback from a group of friends convinced me that I was on the right track and with a group exhibition planned for later this year, that I had a project worth pursuing.

My quest for exhibition quality salt prints took a step futher at the weekend with a marathon two-day darkroom session and a reworked process involving carefully selected art paper, gold toner and the usual large measure of luck.

Paper preparation and exposure

  • Image: Digital negatives prepared from Ilford FP4+ 4×5 sheet film.
  • Paper: Daler Rowney, The Langton Prestige 300gsm HP.
  • Salt solution: 2% sodium chloride applied by foam applicator.
  • Sensitiser solution: 1ml of 12% silver nitrate applied by pipette and hake brush.
  • Exposure: UV face tanner, time determined by test strip.

Print processing

  • Pre wash: tap water, 10 minutes with frequent agitation.
  • Salt bath: 1% sodium chloride, 30 seconds with agitation.
  • Wash: tap water, 10 minutes with frequent agitation.
  • Toning bath: Tetenal Goldtoner diluted 1:4, 5 minutes.
  • Wash: tap water, 5 minutes, frequent agitation
  • 2-bath Fix: 15% hypo with 0.25% sodium carbonate, 5 minutes each bath with agitation.
  • Wash: tap water, 5 minutes with agitation.
  • Hypo clear bath: 1% sodium sulphite, 5 minutes with agitation.
  • Final wash: tap water, 60 minutes.
  • Dry.

The above process was adapted from that detailed in the book The Salt Print Manual by Ellie Young. Limitations to space, resources and availability of materials necessitated some compromises:

  • For each wash I used single 40-litre plastic storage boxes rather than a two-tray set up with running water,
  • I used a ready made product, Tetenal Goldtoner, which I diluted to strength, rather than preparing toner with gold chloride solution which I simply couldn’t source in the UK,
  • My local craft supplies store does not stock any of the tested art papers recommended in the book but did stock The Langton Prestige 300gsm HP paper which met the specifications for being 100% cotton, acid free, gelatin sized and of sufficient weight to withstand all the washing.

I wanted to have a defined coated area which the negatives would overlap slightly, thus avoiding the sharp, straight edges of the negatives showing on the print. To achieve this I formed three masks from mountboard, one for the salt solution, one for the sensitiser and one to position the negative. By using separate masks I avoided contamination between the coatings. Once sensitised, the paper has to be exposed within two hours so I split my workflow into two batches, preparing four sheets at a time.

The first print was not much success, showing staining where the drops of silver nitrate from the pipette had fallen on the paper and then been poorly spread with very obvious brush marks. The second print was better and from the third print onwards results were very acceptable although by the final three, shadows were blocking up and the prints were becoming quite dark, a sign of too much silver.

I concluded that I had not sufficiently wetted the hake brush before starting and so for the first sheet it had absorbed rather than spread the silver nitrate sensitiser. As the session progressed the brush was carrying over a combination of salt and sensitiser from one sheet to the next leading to too great a concentration on the later sheets. I also noticed that the bristles on the hake brush became clumped together and because the brush strokes were constrained to the image area by the mask, this led to a grid-like pattern of sensitiser application, most noticeably around the edges and corners of the prints.

First negative printed: On left, sensitised with foam applicator. On right, sensitised with hake brush.

There was just enough silver nitrate solution left over to make a second print from the first negative. This time I spread it with a well wetted clean foam applicator. Unfortunately the paper was rather hurredly coated and each coat was not properly dried before exposing the paper which led to some dark banding in the finished print. However it did show me the difference that using slightly less sensitiser and a different applicator could make.

A couple of days later I had the opportunity to show the set of dried prints to my group of friends. It was interesting to observe their reactions and useful to hear their feedback. Perhaps I should not be surprised to find that prints I would have discarded are aesthetically pleasing to others!

I am greatly encouraged that my marathon darkroom session was not in vain. I’ll need to plan soon for the next one!


Every first attempt has a silver lining

First attemps at making salt paper prints.

It is almost a month since I reported on my participation in a contemporary salt print workshop. Keen to put what I discovered into practice I’ve been gathering together the bits and pieces I would need that I don’t already have and also gathering images that I imagine would look good when printed on salted paper.

The weather over the past couple of weekends has been favourable so I’ve been out and about with my Intrepid field camera and have a good selection of 5×4 negatives to print from. The ‘contemporary’ process takes a scan of the original negative and with some editing in Photoshop produces what should be an optimised digital negative from which to make the final print. The digital element of the process has the added advantage of producing a digital negative of a size larger or smaller than the original and also means that the source image can be from a digital camera.

IMG_5456A few months ago I had been gifted a quarter-plate contact printing frame and saw my salt print experiments as an ideal opportunty to use it, so I would need to reduce my 5″x4″ negatives to 4¼”x3¼”. However, I don’t use Photoshop so first I had to rewrite the workshop instructions for what I do use, Serif Labs Affinity Photo – Basic digital negative preparation in Affinity Photo. The exposure time would be determined by a test strip to identify the exposure required to achieve maximum black. For maximum control of the highlights, in Photoshop / Affinity Photo and curve to create a denser negative together with a colour screen are applied. The instructions refer to a generic colour screen, which I used for this exercise, but in the workshop we created custom values by exposing a colour spectrum, processing the result, then finding the colour that equated to the brightest highlights.

I can’t say I fully understand the colour screen step and so I started off by picking an image from which I created four digital negatives, one as unscreened greyscale, and the other three screened with varying RGB values: 255:50:0, 50:255:0 and 25:50:0. These are shown below together with the print made (spot the schoolboy error – I overlaid captions on each negative but forgot to flip them!). The four were exposed and printed as one so the only variable affecting the print is the colour screen applied to each digital negative.

My darkroom space is rather limited (its primary function is a shower room) and has to be set up according to the needs of the process being undertaken. For salt printing, the preparatory function of cutting paper to size and coating it with a 2% sodium chloride solution could be performed elsewhere. However sensitizing the paper with 12% silver nitrate solution and processing the exposed paper have to be carried out under safelight conditions. Exposing the paper can be carried out either under the controlled conditions of a UV light source such as my adapted face tanning unit, or under sunlight ideally with a UV index of at least 4. Here in Scotland that amounts to a couple of hours either side of mid-day during the summer months … if we’re lucky! However it is to be exposed, the sensitized paper has to be kept in the dark until ready for exposure.

For my screening-test negatives I had my UV unit set up in the darkroom alongside my processing trays with just a small working area left to sensitize the salted paper with silver nitrate. This gave me a number of problems: the small working area, the wait in the darkroom for the sensitized paper to dry and once the UV unit was on I realised that the inevitable light leaks from it would potentially fog any other sensitized paper whether awaiting exposure or in the process of development. For the test, I was working with only one piece of paper but I would need to rethink my setup for making a series of prints.

I knew that to make any reasonable assessment of my test I would need to allow the print to dry down overnight so I stored my processing solutions (3% sodium chloride and 10% hypo fixer) in light- and air-tight bottles, restored the shower room and went off to sleep on a solution to the darkroom layout.

BFrom my test I decided to stick with RGB values of 255:50:0 and set about creating fifteen digital negatives. I laid them out five to a sheet of Permajet inkjet transfer film with the layout such that I could easily cut out the individual negatives.

I decided that this time I would set up my darkroom for safelight operations only and have the UV light box just outside in subdued light. I reckoned that a little exposure was inevitable but probably of negligible effect (and with hindsight I was right!). When I explored making dry glass plates about a year ago I had aquired a small shallow-drawer unit for drying the emulsion-coated plates and decided to use it as storage for the sensitised paper as I waited for it to dry. This way I could sensitize paper for the session then clear my work area of silver nitrate solution, pipette and brushes.

For the screening test I had run a test strip to determine an exposure time of 5½ minutes and decided to use that as a starting point. The only difference would be that the screen test was done in a 10″x8″ ‘modern’ contact printer while this session I would be using a vintage quarter-plate printing frame with much thinner glass that sat about 1cm further below the UV light tubes. I was also a little uncertain as to how my hypo solution would have fared from being stored overnight as it does not have much ‘shelf-life’.

Processing one image at a time (I have only one contact printing frame!) the first few prints came out of the UV light looking very dark and overexposed. That was to some extent to be expected and they would lighten up as they were processed through the salt bath and hypo fixer before rinsing. However they did not lighten up as much as I would have expected or wanted and so I reduced the exposure time as I worked through the negatives, down to five minutes, then four and a half and the final images just four minutes.

The colour of the prints changes as the process progresses and ultimately as the prints dry down they take on the typical sepia tone that I would expect. There’s a bit of bronzing to some of the prints which is likely due to the age of the fixer and inconsistencies in fully covering the paper when coating are apparent. I consider these all marks of individuality and a part of the image!

What I’m not too happy with is the loss of shadow detail in my prints. I suspect this is due to the curve I have applied when creating the digital negative rather than to the UV exposure given. When creating the digital negatives I adjusted the curve as I would for a ‘normal’ image whereas a negative for salt printing needs good shadow exposure and detail, does not need to be high contrast and needs sufficient density to allow silver chloride to change into metallic silver during exposure. If I have failed in creating the prints I had expected I suspect that this is the area in which I can make the most improvement. That said, for a first attempt under my own steam, the fifteen prints I made do have a ‘look’ and a ‘feel’ that I like.

The final fifteen, 24 hours on from UV light box exposure and processing.

I coated and sensitized three more pieces of paper than I used. These lay in the drawer shaded from light ready to be forgotten about. However as I type up my exploits a day later, the sun is shining and according to the BBC the UV index should be about 3. Surely worth a try to see what an exposure to sunlight might do. I selected three of my favourite images, made up some fresh salt bath and hypo and exposed them one at a time for fifteen minutes each. Here’s how they look now that they’ve dried down a bit.

Three ‘bonus’ prints, a couple of hours after exposure by sunlight and processing.


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


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.