Salted Paper Print (Salted Paper Print) Talbot classical photosensitive printing process and homemade silver salt emulsion coating

1. The starting point of the negative-positive photography system: Tarbert’s great invention

In 1839, British scientist William Henry Fox Talbot invented the Calotype/Salt Print method:

1. Revolutionary significance that is different from the Daguerreotype:

• The Daguerreotype is the production of a unique direct positive print on a metallic silver plate that cannot be reproduced;
• Tarbert first invented the concept of negative to positive. A negative can be printed and copied infinitely on salt paper, laying the technical foundation for the modern photography industry.

2. Unique visual aesthetic charm:

• Salt paper does not have the gelatin or plastic coating of modern photo paper, and the photosensitive silver salt is directly infiltrated into the pure cotton fiber of the paper;
• The image is deeply embedded in the texture of the paper. The highlights are the warm ivory yellow of the cotton and linen paper base. The shadows are extremely elegant reddish brown, chocolate or eggplant purple. The matte texture is full of classical poetry.

2. Paper selection and salting pre-coating (Salting Step)

1. Pure cotton acid-free art paper (100% Cotton Rag Paper):

• Pure cotton watercolor paper that has not been bleached by heavy acid must be used (such as Arches Platine, Fabriano 5, etc.);
• The lignin and alkaline buffer (such as calcium carbonate) inside the paper will react with the photosensitive silver salt, so neutral pure cotton paper must be used.

2. Saline pre-coating solution preparation:

• Distilled water: 500ml
• Pure sodium chloride (preferably high purity iodine-free edible salt or ammonium chloride): 10g
• Gelatin (or potato starch, as color-preserving film-forming adhesive): 2g
• Sodium citrate (to adjust contrast and tone): 5g

3. Practical operation of dip coating:

• Dissolve gelatin in distilled water at 40°C, add salt and sodium citrate;
• Lay the entire piece of watercolor paper flat and float on the surface of the salt water tank for 3 minutes to ensure that the fibers are completely saturated with salt water;
• Hang to dry in the shade, salted paper can be stored for several months in a dark and dry environment.

3. Chemical sensitizing coating (Sensitizing with Silver Nitrate)

Do this under safe yellow light or weak incandescent light in a darkroom:

1. Silver nitrate sensitized aqueous solution (12% concentration):

• Distilled water: 100ml
• Optical grade silver nitrate crystal (Silver Nitrate): 12g
• Citric acid crystal (anti-spontaneous fog acidifier): 6g

2. Traditional Hake Brush Coating:

• Lay the salted paper flat on the dust-free glass plate;
• Use a graduated dropper to draw about 2ml of silver nitrate solution to form a liquid line on the paper;
• Hold a metal-free Japanese wool brush (Hake Brush) and use gentle criss-crossing techniques to quickly brush evenly;
• Chemical and physical replacement reactions occur instantly:
  [NaCl + AgNO_3 \rightarrow AgCl\downarrow + NaNO_3 ]
• Water-insoluble microscopic silver chloride (AgCl) crystals instantly precipitate and precipitate in situ in the microscopic grooves of the paper fibers!
• After coating, place it in an absolutely light-proof drying box to dry naturally.

4. Ultraviolet contact exposure and printing-out process (Printing-Out Process)

Salt paper printing belongs to the "Printing-Out / POP" process and does not require any developer at all!

1. Photochemical miracles visible to the naked eye:

• Press the high-density large-format negative film and dry sensitized salt paper into the split-back printing frame;
• Expose to sunlight or UV plate machine (sunlight takes 5 to 15 minutes);
• Silver chloride is directly reduced to metallic silver elemental colloidal particles under the bombardment of extremely strong ultraviolet photons;
• Open one side of the back of the printing frame, and you can directly observe the progress of the printed image with the naked eye under red light. The exposure should be deliberately slightly darker by half a stop (because subsequent fixation will wash it out).

5. Gold toning and low-concentration fixation preservation

1. Gold Toning:

• The newly exposed salt paper image shows reddish elemental silver particles that are easily oxidized;
• Soak the print in a very thin gold chloride toner (Gold Chloride + ammonium thiocyanate) for 3 to 5 minutes;
• The noble metal gold ion atoms are replaced and wrapped on the surface of the silver particles. The picture instantly changes from brick red to extremely luxurious and deep purple gray and pure black, and the chemical stability is increased several times.

2. Plain Hypo Fixing:

• It is strictly prohibited to use modern acidic quick fixers (Acidic fixers will completely bleach and destroy the delicate and delicate salt paper silver image in an instant!);
• A mild neutral fixing solution of 10% pure sodium thiosulfate (hypo) and a small amount of sodium sulfite must be prepared;
• The fixing time is strictly controlled at 3 to 5 minutes, followed by extremely thorough running water washing and drying, and an original silver salt art print masterpiece that can span two centuries is born.

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