Notes on Salt Printing
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Why You Should Never Make Salt Prints on Unsized Paper
If there’s one mistake I’ve made more times than I care to admit, it’s trying to shortcut the sizing stage when making salt prints. Trust me — don’t. Salt prints and unsized paper simply don’t mix.
Sizing your paper properly is absolutely essential. Without it, the chemistry soaks in unevenly, and you won’t realise anything is wrong until you start exposing your prints and notice those dreaded pale, patchy areas. It’s incredibly frustrating — especially if you’ve carefully prepared ten sheets only to discover they’re unusable.
Making a Proper Gelatine Size
I use a simple 2% gelatine solution. It’s straightforward but worth doing carefully.
I start by weighing out 2g of gelatine and mixing it into about 30ml of water. Once it’s fully dissolved, I leave it to sit for around ten minutes to bloom. Meanwhile, I heat another 70ml of water to roughly 50°C and then combine it with the gelatine mixture to make 100ml in total.
The solution works best when applied at around 40°C. A hotplate with a magnetic stirrer makes life much easier here. If I have leftover sizing solution, I store it in the fridge. It will set solid, but that’s normal — just warm it gently before using it again.
When brushing on the size (especially with a foam brush), I always make sure the brush is slightly damp. A dry brush can give the illusion of even coverage when in reality you’ve missed areas. That mistake only reveals itself later under UV light — and by then, it’s too late.
Once coated, I let the paper dry completely before moving on.
Salting the Paper — And Why the Salt Matters
After the gelatine has dried, it’s time for the salt solution.
I mix a 2% sodium chloride solution — 2g of salt dissolved in 100ml of distilled water at room temperature. Not just any salt will do. It must be free of additives like iodine or anti-caking agents. I use pharmaceutical-grade sodium chloride to avoid any unwanted surprises.
To coat the paper, I pour a small amount (about 3ml) into a dish and apply it with a slightly damp brush, working both horizontally and vertically to ensure even coverage. Then it’s left to dry for about an hour.
Sensitising: Where Things Get Serious
Once the salted paper is fully dry, I prepare the sensitiser.
I mix roughly 2ml of 12% silver nitrate solution with 2ml of 6% citric acid in a small glass container. Never metal — silver nitrate reacts with it. A glass rod or plastic spoon works perfectly.
I pour the mixed solution into the centre of the sheet and brush outward in vertical and horizontal strokes, again using a slightly damp brush to avoid streaks. The key here is even coverage, especially over the area that will hold the image from the digital negative or photogram.
Then it’s another wait — about an hour to dry.
Exposure — Reading the Print
Exposure times vary dramatically depending on your UV source. With my UV exposure unit, most prints fall somewhere between eight and ten minutes. Sunlight is far less predictable and depends heavily on the UV index.
I sandwich a high-contrast digital negative against the sensitised paper under a weighted sheet of glass. If I’m using a contact frame, I’ll carefully lift one side to check progress without shifting the negative.
I aim for the image to appear one to two stops darker than I ultimately want. The washing and fixing stages will lighten it slightly, so it’s better to expose a little further than you think.
The Wash — Watching the Silver Leave
This is always an interesting moment. As soon as the print hits the water tray, the unexposed silver washes away, clouding the water slightly. I change the water two or three times until it runs clear, which usually takes around three to four minutes.
Then the print moves into a 10% sodium thiosulphate (hypo) bath for about five minutes with occasional agitation.
After fixing, I give it a thorough final wash — either fifteen minutes under running water or several tray changes if I’m trying to conserve water.
The Final Reveal
Once washed, I hang the print to dry.
There’s something deeply satisfying about this process. Salt printing is simple in principle, but it rewards patience and punishes shortcuts. Every stage matters — from properly sized paper to careful brushing and watching the exposure deepen under UV light.
And if there’s one lesson I’ve learned the hard way: always size your paper properly.