Inside the Ammonio-Nitrate of Silver Print: An 1840s Salt Process for My Adamson Calotypes

When I say my prints are “ammonio-nitrate of silver salt prints,” I’m not just dressing up a basic salt print with fancy words.

I’m using a very specific 1840s variant of Talbot’s salted paper process, built on a silver–ammonia complex that people like Alfred Swaine Taylor, Talbot, and the Hill & Adamson circle actually used.

This matters because:

• The chemistry really is different from a plain silver nitrate salt print.
• The look is different: deeper blacks, richer midtones, and a warm, slightly smoky tone.
• It pairs perfectly with dense, atmospheric Adamson-style 1843 calotype negatives.

This article walks through what ammonio-nitrate of silver is, how it differs from a regular Talbot silver-chloride print, and the workflow I use in my darkroom today.

Where Ammonio-Nitrate of Silver Fits in History

Talbot’s Salt Print: The Baseline

Talbot’s early “photogenic drawings” and later salted paper prints work like this:

1. Soak fine writing paper in a weak salt solution (usually sodium chloride).
2. Dry the paper.
3. Brush a strong silver nitrate solution on the salted side.
4. The silver nitrate reacts with the salt in the paper to form silver chloride in the fibers.
5. Under UV/light, silver chloride darkens to metallic silver; the image slowly prints out.
6. The print is stabilized and fixed with strong salt, then sodium thiosulfate (“hypo”), and washed.

This is the “plain silver” salt print most people think of: slow, gentle, and often light-toned, with soft Dmax and beautiful but delicate midtones.

Taylor’s Ammonio-Nitrate of Silver

By 1840, chemists and photographers were pushing that process harder. Alfred Swaine Taylor, a toxicologist and early photographic experimenter, published a pamphlet in 1840 arguing that “ammonia-nitrate of silver” was better suited to photogenic drawing than plain silver chloride.

Key points from Taylor and later technical histories:

• He added strong ammonia, drop by drop, to a silver nitrate solution until a brown precipitate formed and then re-dissolved, leaving a clear ammonio-nitrate of silver solution.
• On slightly salted paper, this ammonio-nitrate solution produced prints that came up faster and reached a higher density than plain silver nitrate.
• By mid-century, “ammonia-nitrate” silver baths were widely used for salted papers, especially when printing from weaker negatives.

So ammonio-nitrate isn’t a modern tweak. It’s a documented 1840–1860 working method with a paper trail in both chemistry books and actual surviving prints.

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The Chemistry in Plain Language

Regular Salt Print Chemistry

In a plain silver-chloride salt print, the key reaction is:

• Salt in paper (NaCl or NH₄Cl) + silver nitrate (AgNO₃) → silver chloride (AgCl) + a leftover nitrate salt.

Silver chloride is the light-sensitive compound. Under light:

• Silver chloride breaks down into metallic silver (the image) and chlorine. The tiny silver particles in the paper form the image tone.

The paper is slow but stable if fixed and washed well.

What Changes With Ammonio-Nitrate

When ammonia is added to the silver bath until the brown precipitate dissolves, you get a clear silver–ammonia complex, often written as [Ag(NH₃)₂]⁺ in solution.

On salted paper:

• The chloride in the paper still reacts with the silver to form silver chloride.
• But now the silver is delivered and “held” by the ammonia complex, which changes how fast and how fully it reduces to metallic silver under light.

Technical histories sum it up like this:

• Ammonia-nitrate sensitized salted papers give a more “brilliant, vigorous” image, and are especially useful when printing from weaker negatives.

Side effects the conservation literature notes:

• The solutions yellow and go off faster than plain silver nitrate if you keep them too long.
• Poorly processed prints (weak fixing, short washing, bad storage) can yellow more quickly.

In other words, the chemistry gives you more punch and speed, but demands tighter discipline in processing and storage.

A Historical Ammonio-Nitrate Formula (With Metric Equivalents)

One 19th-century description, quoted in later writing, describes Talbot’s use of ammonio-nitrate this way:

Paper “prepared with K I (3 or 4 oz. to 1 gallon of water) and the ammonia nitrate of silver (50 grains of nitrate to 1 oz. of water, ammonia being added to form a precipitate, and redissolving the same, leaving the solution clear)….”

Translated:

• 50 grains silver nitrate ≈ 3.24 g
• 1 ounce water ≈ 28–30 ml

So a typical historical ammonio-nitrate sensitizer is roughly:

• About 3.2 g silver nitrate in 30 ml distilled water (about 10–12% w/v),
• Strong ammonia is added dropwise until the brown silver oxide precipitate forms and then clears, leaving a transparent solution.

That’s the same chemical move I use in my own darkroom, scaled to my preferred working volumes and papers.

My Ammonio-Nitrate Salt Printing Workflow

I keep the structure faithful to the 1840s, but use modern distilled water and consistent metric measurements.

Salt the Paper

1. Choose a good, smooth, 100% cotton paper.
2. Mix a dilute salt solution
3. Float or brush the solution on the paper, ensuring even coverage.
4. Dry completely and store flat.

This step creates a reservoir of chloride in the fibers, the same way Talbot salted his paper before sensitizing.

Mix the Ammonio-Nitrate Sensitizer

Starting point (historical scale):

• 3.2 g silver nitrate
• Distilled water to 30 ml

Then:

1. Dissolve the silver nitrate fully in distilled water.
2. Add strong household-grade ammonia (concentrated) drop by drop, with constant swirling.
   • A brown precipitate will form (silver oxide).
   • Keep adding ammonia until this precipitate just redissolves and the solution becomes clear again.
3. If you want to be very close to 1840s practice, add some acetic acid to nudge the solution back to slightly acidic. Several 19th-century manuals suggest this to tame fogging and I have also found this to be true.

At this point, you have a working ammonio-nitrate silver sensitizer.

Sensitize the Salted Paper

1. In dim tungsten or safelight conditions, brush or float the salted paper in the ammonio-nitrate solution.
2. Aim for an even, glossy wet surface; avoid puddles and dry streaks.
3. Let the paper drain and air-dry until the surface is dry but still cool to the touch.

This freshly sensitized sheet will print faster and to a higher density than if you had used plain silver nitrate on the same salted paper.

Print-Out Exposure

1. Contact print your Adamson-style calotype negative in a printing frame against the sensitized sheet.
2. Expose under UV or direct sun.
3. Print “deep” — darker than the final tone you want — because later clearing and fixing steps will lighten the image.

Because of the ammonio-nitrate sensitizer, you’ll see the image come up more quickly and with stronger shadows than a plain salt print.

Post-Exposure Clearing Baths

Here’s the sequence I use, which is tuned to both color and permanence:

1. 1% salt bath at 20°C for ~3 minutes
   • This gentle salt solution helps dissolve residual silver salts near the surface, opening the highlights and controlling overall warmth.
2. Two hot water baths at ~60°C, ~3 minutes each
   • These hot washes move more of the residual soluble silver out of the paper and help stabilize tone.
   • They also shift the color slightly, giving a deeper, less chalky appearance.

This kind of salt/hot-water clearing routine fits with 19th-century attempts to improve permanence and color in salted prints, even though individual recipes varied.

Potassium Iodide Bath

Sometimes I use a dilute potassium iodide (KI) bath at about 20°C for anywhere between 30 seconds and 2 minutes.

Chemically, this does two things:

• Converts some leftover silver chloride into silver iodide or mixed iodo-chlorides, which are less light-sensitive.
• Lightly bleaches and stabilizes the image, shifting the tone toward warm brown-yellow while protecting highlights.

Talbot himself experimented with KI baths after exposure to stop further darkening and improve stability; you’re extending that logic inside an ammonio-nitrate workflow.

Fixing

I fix in two successive hypo baths (sodium thiosulfate):

1. First hypo bath, relatively low strength (for example, 2–5% w/v), a few minutes with constant agitation.
2. Second fresh hypo bath, same strength, for similar time.

The goal:

• Remove as much unexposed silver chloride / silver complex as possible without stripping image silver.
• Spread the load across two baths so the fixer in each is not overwhelmed.

Historical sources show salted paper prints were traditionally fixed in hypo (Talbot’s circle and later printers), and modern conservation work confirms that thorough fixing and washing are critical to long-term stability.

Final Wash and Drying

1. Extended wash in running water or multiple still water changes, long enough to remove residual hypo (~6 to 8 hours, depending on method).
2. Blot, dry flat, and press if needed.

We know that many 1840s ammonio-nitrate salted prints have survived in good condition for more than 180 years. That tells us that, despite warnings about yellowing in the literature, careful processing and storage can yield very stable results. Hill and Adamson’s ANS prints are held by several museums, universities, and collectors and continue to remain in excellent condition.

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How This Differs From a Plain Talbot Salt Print (And Why I Care)

Side-by-side, here’s what changes:

1. Print speed and density
   • Plain salt print: slow; Dmax can be modest unless everything is perfect.
   • Ammonio-nitrate: faster printing, deeper blacks, better from dense Adamson calotypes.
2. Tone and midtones
   • Plain: soft, often lighter, sometimes “thin” if negatives are heavy.
   • Ammonio-nitrate: richer midtones and slightly warmer, more “velvety” tone, especially with your KI and hot-water sequence.
3. Match to Adamson-style negatives
   • My Adamson calotypes are dense, high-contrast, and atmospheric.
   • The ammonio-nitrate print pulls full scale out of them without resorting to modern contrast tricks; it stays inside an 1840s logic.
4. Historical lineage
   • Plain salt print alone is Talbot’s early baseline.
   • Ammonio-nitrate of silver is an early, documented upgrade in that same decade, used by people like Taylor and folded into the broader practice around the Hill & Adamson era.

So when I say, “This is an ammonio-nitrate of silver salt print from an Adamson-style calotype,” I mean:

• The negative is a true calotype, not a generic paper negative.
• The print is a specific 1840s salt process that uses a silver–ammonia complex to get the tonal voice I want.
• The workflow sits on a historical foundation, not a modern shortcut.

Why I Use This Process For My Work

For my own projects, especially the Adamson-era calotype work, this process gives me:

• The tonal depth to match dense window-light calotypes.
• A warm, layered look that feels closer to drawing or etching than to a modern digital print.
• A direct line back to 1840s practice that I can explain in honest, concrete terms to collectors.

It’s slower. It’s fussier. But it’s the right tool for the negatives I’m making and the stories I’m trying to tell.

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