Learning the Salted Paper process - Part I

In this series, I'm trying to document my progress of learning the 19th-century photographic printing process called salted paper printing. It was invented by Englishman William Henry Fox Talbot in 1834 and its details made public in 1839 shortly after the news arrived from France of Louis Daguerre inventing the daguerreotype. Depending on which source you read, it is one of these two processes that is credited with the invention of photography.

The negative

Negatives suitable for salt printing need to be very dense and high contrast, so much that they can't even be used anymore for traditional silver gelatin enlargements.

I tried to achieve this by taking a roll of FP4+ (box speed ISO 125) and shooting it at ISO 25, which would result in 2⅓ stops overexposure. Trying to get even more density I tried to overdevelop the negatives by 33%. According to the Massive Dev Chart FP4+ in my trusty Rodinal 1+50 takes 9 minutes, including the 33% overdeveloping I set the timer to 12 minutes.

Treptower Park, Berlin

On the day I took these pictures there was heavy fog and the visibility was probably around 25 meters. The dynamic range of each of these frames was somewhere around 4-5 stops, not the best situation for high-contrast negatives. Looking at the negatives, rather than the scans, I decided to try out strip 3 and 4.

Preparing the paper

Some research concluded that Hahnemühle Platinum Rag paper seems to be working great for salt printing, so I went ahead and used this. It seems to me that it has a bit of a yellow tint to it, I'm not sure yet if I like the colour or not.

I got the chemicals from MAMUTphoto, a specialist for alternative processes. The package included a salt solution (containing sodium chloride and sodium citrate), a silver nitrate solution, a citric acid solution, and a fixer (containing sodium thiosulphate and sodium carbonate).

The night before, I cut one sheet of 8x10 inch paper in half and coated each side with 1ml of the salt solution with a brush, trying to get an even coating. I made sure to brush on the salt solution in even strokes from left to right, top to bottom, right to left top to bottom, top to bottom right to left, and bottom to top left to right, occasionally I turned the brush to make sure both sides are in contact with the paper. Coating with even pressure over the whole brush stroke seems to be quite a challenge, as there are some streaks visible in the finished print that I think result from the salt coating.

The next day in the photo lab I set everything up in the darkroom to coat the dried and salted paper with silver nitrate. I used the same brushing technique as the evening before, but this time with a brush that does not contain any metal to avoid contamination.
I coated the first print with 1ml of silver nitrate, and in retrospect, I have brushed for too long, towards the end the brush was partially dry so there were some streaks appearing where there was more silver nitrate coating than in other areas. For the second print, I decided to go for more silver nitrate, 1.5ml, and to stop brushing before it dried, this seems to have worked a bit better.

Exposing the print

The next step was getting the negative, and a 21 step wedge onto the sensitised and dried paper, the emulsion side in contact with the paper. Putting this into the contact printing frame turned out to be quite a bit harder than it should be, next time I will get some white cotton gloves so I won't feel bad touching the surface of the negative.

Since it was a grey and rainy day I used the UV table of the screen printing section of my lab which consists of an array of six 40W UV tubes. Every five minutes I checked that the step number 1 of the step wedge, which is basically a transparent film base, against the area outside the negative. With the goal to stop the exposure when they are the density. I decided the exposure to be adequate after 30 minutes as I saw a metallic green hue appearing which seems to be due to bronzing, at which point the print will start to become overexposed.
As the finished print is lacking quite a bit of contrast, I decided to push it further with the second print and went for a 50 minutes exposure, the same metallic green hue started appearing at around 30 minutes, but seems to not be visible when I took the frame out of the dark room into normal daylight.

Checking the density during the exposure in a contact print frame, half of the frame opens up while the other half is still holding the paper onto the negatives.

Washing and fixing

Once the exposure is finished, I took the paper out of the frame and washed it with water for 15 minutes in a tray, frequently changing the water. This is especially important in the beginning when the water turns cloudy, which is unexposed silver chloride and silver nitrate. After that, I put the print for 30 seconds into the same salt solution that I used for the first coating, and then back into the water for about 8-10 minutes.

At this stage, the print typically gets toned, for example with a gold toner, which not only intensifies the image but also increases the life span of the print. I decided not to tone my first few prints, to get a feeling for the basic process first before I start adding another variable into the mix.

I first put the print into a bath of hypo fixer (sodium thiosulfate and sodium carbonate) for four minutes, and then into a second bath of the same, but fresh fixer. The last washing step is to remove the fixer from the paper which I did by putting into our print washer for about an hour.

Finished prints

Three Trees, Salted Paper Print, 2017

White Noise, Salted Paper Print, 2017

Next steps

The first print (Three Trees) is clearly underexposed, and the negative could benefit from more contrast, but for the first salt print I ever did I'm quite satisfied with it.
I'm very happy with the second print (White Noise), the exposure seems to be correct, the negative seems to work well, although it could maybe be even a bit more dense.

As for my next steps I want to test out the Three Trees negative again with two prints:

  1. 1ml silver nitrate and longer (towards 50 minutes) exposure
  2. 1.5ml silver nitrate and longer (towards 50 minutes) exposure

And from looking at both of these prints, I definitely have to work on my brush technique.