Salt Prints

It’s been a busy week here in quarantine-land!

Jakob (my son, now a 9th grader) is in a one-week mini-course exploring experimental photography. Since we’re all in lockdown for COVID-19, the two of us have been exploring what’s in my dimroom and revisiting some of the easier processes as an intro to alt-photography. And in true going-back-to-basics style, we’ve rewound back to salt prints.

I love the story behind salt prints. As I’ve read in multiple places, the story is that Henry Fox Talbot was on honeymoon in 1833 and wanted to preserve the idyllic landscape. The method d’jour was to use a device called a camera lucida (a prism fixed in place so the viewer could see the scene in front of them, while also seeing a piece of tracing paper below) to trace a copy of the live image, and for the artist to fill in the details using their rendering skills. Well, Talbot was not good at drawing and didn’t have those skills; his rendition, while still being better than mine would have been, was not very elegant. And so he became obsessed with the idea of fixing an image on paper. “The idea occurred to me, how charming it would be if it were possible to cause these natural images to imprint themselves durably, and remain fixed upon the paper.”

And the rest is literally history. Talbot pulled together ideas that had existed for roughly a hundred years and, by 1835, had a working process to make a photo. With the help of Sir John Herschel (apparently help that was not so immediately accepted), they had worked out a fixer and he was able to make the images permanent by 1842.

While Kallitypes still hold my heart for favorite process – and are amazing to demonstrate because of the dramatic reveal in the developer – salt prints are so straightforward that they seemed a better fit for an intro-to-alt-printing. So here’s the recipe I use.

Part 1: mix…
20g kosher salt
20g ammonium citrate
200ml cool distilled water

Part 2: mix in a 1 liter container:
8g gelatin
600ml cool distilled water

Let Part 2 bloom for a half hour, and then melt it slowly over a gentle heat (I bring it up to about 125 degrees F). Mix in Part 1, and then fill it to 1 liter with more cool distilled water.

I prefer Bergger COT 320 paper for this process. After pouring the liter of solution in to a developing tray, take a stack of paper; one at a time, immerse them in the solution for about 10 seconds, flip, and 10 more seconds; then hang it to dry. Repeat for as many sheets of paper as you like.

I’m smitten with smaller salt prints. Once the sheets are dry, I like to cut them in to quarter sheets before sensitizing them; there’s something… romantic? idyllic? poetic? … about a 4×5 contact print, right off of a large format negative.

To sensitize one 4×5 – and after marking the corner of the side I intend to sensitize, because it’s impossible to tell the sides apart – I put about 0.67ml of 10% silver nitrate (“one dropperful” for the droppers I use to store working silver nitrate solution) along one of the short sides of the paper, and then use a foam brush to spread it over the paper. A cheap 4″ foam brush covers the paper well, and after you’ve sensitized a couple of them in a row is merrily pulling the excess from one sheet to the next.

If you, like me, are going to keep that foam brush between uses – just be very careful to clean it well (with distilled water) and I would not recommend using that brush for any other chemistry. As a rule, I don’t re-use any of my foam brushes for other chemistry, although for many of them it really doesn’t make much of a difference – but this particular case is different, since the silver, if not cleaned well enough, will start staining everything else black.

If you’ve ever exposed cyanotypes or blue art print paper in the sun, you’ve experienced the simplicity of timing the exposure – set it in the sun until you see it change color the way you want, and then develop it. Salt prints can be done the same way. The exposed areas darken and, with a little practice, you can get in the ballpark of a good exposure by watching it. Personally I use a UV meter (because I’m a data nerd) and like to expose negatives between 4000 and 10000 units, depending on the negative. Something between 2 and 5 minutes in the bright sun.

The print is, at this point, developed; it just needs washing and fixing for permanence. I like to wash in multiple baths of 1% citric acid, although that’s not strictly necessary – you could just use gently running cool water – and then I fix for about 10 minutes in whatever sodium thiosulfate fixer I’ve made (5% sodium thiosulfate) and washed (longer is better for archival reasons, a full hour if you want to be sure).

As a bonus, the same gold toner I use for kallitypes works with salt prints. After washing and before fixing, a quick dip in some of this (which I find to be very re-usable) significantly darkens the prints:

700ml cool distilled water
50ml 1% gold chloride
50ml 1% thiourea (or 0.5g)
0.5g tartaric acid
cool distilled water to make 1000ml

Salt prints – left is untoned, right is toned with gold toner.

Once used, if you’re keeping it for re-use, store it in a separate bottle so as not to contaminate your supply. I’ve had stock mix sit for 6 months and still work great, but once it’s used, it doesn’t last that long.