Iron Silver Printing Method (Kallitype Print) Classical Printing: Low-Cost Alternative to Precious Metals and Tonal Stability

1. The economic dilemma of classical printing and the birth of the iron-silver printing method (Kallitype)

In the classical photography process, platinum/Palladium Print is regarded as a masterpiece for its unparalleled deep gray tone and thousands of years of storage life. However, its raw materials, platinum salt and palladium salt, are more expensive than gold. The cost of printing an 8x10 photo is as high as several hundred yuan:

1. 1889 invention by Dr. W.W.J. Nicol:

• Invented a process that uses cheap photosensitive iron salts to drive the reduction of metallic silver - Iron-Silver Printing Method (Kallitype);
• Its chemical reaction mechanism is almost 100% identical to expensive platinum prints;
• The cost is only one-tenth of platinum printing, but it can show deep, cold, elegant, silky smooth tones that are very similar to pure platinum photos!

2. Photochemical reaction kinetics: silver reduction detonated by iron ions

1. Ultraviolet photoreduction of iron oxalate (Photochemical Reaction):

• The core of the photosensitive agent is Ferric Oxalate;
• Under the bombardment of ultraviolet photons, ferric ions ((Fe^{3+})) are excited and reduced to ferrous ions ((Fe^{2+})):
  [ Fe_2(C_2O_4)_3 + h\nu \rightarrow 2FeC_2O_4 + 2CO_2\uparrow ]

2. Avalanche metallic silver precipitation in the developer:

• After exposure, only a weak ferrous latent image remains on the paper;
• The moment it is immersed in the developer, under the strong dissolution and activation of the developer (potassium sodium tartrate / borax), the ferrous ferrous ions show strong reducing properties and instantly reduce the silver nitrate ((Ag^+)) present in the paper to extremely fine elemental silver ((Ag^0)):
  [ Fe^{2+} + Ag^+ \rightarrow Fe^{3+} + Ag^0\downarrow ]
• The photo magically blooms black in one second in the developer!

3. Preparation of photosensitive liquid and coating on pure cotton watercolor paper

1. Professional Kallitype Photosensitive Liquid Classic Formula:

• Solution A: 20g iron oxalate powder dissolved in 100ml distilled water (add 1g oxalic acid to prevent spontaneous hydrolysis);
• Solution B: 10g silver nitrate powder dissolved in 100ml distilled water;
• Pre-use mixing: Under dark red and yellow light, mix solution A and solution B according to the volume ratio of 1:1, and add a drop of potassium dichromate (contrast regulator);

2. Pure cotton paper coating and drying:

• Use a metal-free brush to lightly cross-brush on Ashi watercolor paper;
• After coating, place it in absolute darkness to dry naturally, with the relative humidity maintained at 40% to 50% (too dry will lead to incomplete development, and too wet will cause the solution to penetrate deep into the fiber and reduce the resolution).

4. Adjustment of cold and warm color formula of developer and clear iron removal tank

By changing the chemical formula of the developer, you can freely create fascinating tones on iron-silver prints:

1. Black and white cool black tone developer (Borax/Rochelle Salt):

• Distilled water: 1000ml
• Borax: 70g
• Potassium sodium tartrate (Rochelle Salt): 50g
• Presents cool, deep blue-black and neutral black, with strong contrast;

2. Classic Warm Brown Developer (Pure Rochelle Salt):

• Dissolve 100g of pure sodium potassium tartrate in 1000ml of distilled water;
• Presents a warm chocolate warm brown and rich mid-grey transition just like old photos.

3. Completely remove iron salt precipitation (Clearing Baths - extremely critical):

• After development, it must pass through two consecutive passes of 3% disodium ethylenediaminetetraacetate (EDTA-2Na) or citric acid clear solution;
• Thoroughly complex and clean the remaining ferric ions in the paper fibers, otherwise the remaining iron elements will oxidize, turn yellow and deteriorate in the future.

5. Precious metal toning gives eternal life

Ordinary Kallitype silver images are not as weather-resistant as platinum, but as long as they are precious metal toned, you can get a thousand-year eternal lifespan that is 100% the same as a platinum print:

1. Platinum / Palladium Toner:

• Before fixing, immerse the photo in a dilute acid bath of Potassium Chloroplatinite;
• Metal silver atoms and platinum ions undergo a primary battery replacement reaction, and expensive pure platinum metal atoms wrap and replace the silver image in situ;
• The image instantly transforms into a pure precious metal platinum image, which not only has the low cost of Kallitype, but also has the aristocratic pedigree of orthodox platinum photos that are resistant to strong acids and alkalis and will never fade!

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