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Chemicals used for wet plates

What is Wet Plate Photography?

Wet plate photography, invented by Frederick Scott Archer of England in 1851, was imported to Japan during the late Edo period. Compared to the dominant daguerreotype at that time, wet plate photography became widely popular due to its higher sensitivity and lower cost of photosensitive materials. For about 30 years until the introduction of dry plate photography in the 1880s, various significant figures were captured using wet plates, including Sakamoto Ryoma, Katsu Kaishu, and Emperor Meiji. It was also during this era that commercial photography and photo studios began to emerge.

Wet plate photography is also known as the Collodion process. The specific process involves coating a flat support material such as glass or aluminum plate with a chemical called collodion. The plate is then immersed in a solution of silver nitrate to make it photosensitive. As the term "wet plate" suggests, the plate is only sensitive to light when the collodion is wet on its surface. Therefore, the photographer had to make the exposure promptly and then perform the development process in a darkroom (as sensitivity is lost when the plate dries). After completing the entire development process, varying tones appear on the collodion's surface, creating a photograph that can be appreciated.

Depending on the support material used, if a blackened aluminum plate is employed, it is called a tintype, whereas using a glass plate results in an ambrotype. Tintypes are lightweight and durable, making them suitable for portability. However, one characteristic of tintypes is that text or patterns appear reversed in the image.

On the other hand, ambrotypes can produce a positive image by placing the film side at the back, but they appear as negative images, requiring the viewer to place them against a black cloth or paper for proper observation.

Furthermore, the appearance of the image during development is significantly influenced by the daily condition of the chemicals used and the weather. Fluid patterns (stains) may appear in the image area (mainly at the edges) as traces of chemical reactions, and this is also a distinctive feature of wet plate photography. Thus, each wet plate photograph displays unique characteristics, and no two photographs are exactly the same.

Wet plate photography, Tintype


Wet plate photography, family photo


Basic flow (Ambrotype)

(1) Polish a glass plate thoroughly.

(2) Pour collodion solution onto the glass plate and let it half-dried.

(3) Soak the half-dried glass plate in silver nitrate solution for about 3 minutes. Silver ions in the solution react with the collodion solution to form silver halogens, making the glass plate photosensitive.

(4) The glass plate is loaded into a large camera and photographed (exposed).

(5) The glass plate is removed from the camera and immediately developed and fixed in a darkroom.

(6) Rinse with water and dry. Coat with varnish to prevent from tarnishing and scratching.

More details here

Collodion and Color

  In wet plate photography, collodion serves as the film and its spectral sensitivity differs from what the human eye can perceive. Collodion is sensitive even to ultraviolet light, but its sensitivity decreases around the blue and green range. As a result, colors such as yellow, orange, and red appear darker in the final image.

Collodion, Spectrum

From Quinn Jacobson’s book CHEMICAL PICTURES

  During portrait photography, light blue clothing may appear white, while red or orange clothing can appear almost black. Red lipstick also appears black, so caution is needed. Different colors and patterns exhibit distinctive appearances due to the characteristics of collodion.


Furthermore, the way collodion and black and white film (panchromatic) capture colors is significantly different. Wet plate photography developed with collodion has strong contrast and fewer intermediate gray tones, providing a unique visual quality. In contrast, black and white film converts all visible colors into subtle shades of gray.


  It can be said that the characteristics of collodion contribute to the distinct retro aesthetic of wet plate photography.

Collodion, Spectrum

Black&white film

Color film


Wet plate photography, Ambrotype
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Principle of Wet Plate Photography

Salted collodion

  Collodion is a mixture of nitrocellulose and ether, which is a viscous liquid. When applied to a wound, it forms a waterproof film, making it known as a water-resistant adhesive plaster. Salted collodion, on the other hand, is a solution that includes cadmium bromide, potassium iodide, and additional ether. Salted collodion itself is not photosensitive, but the cadmium bromide and potassium iodide in the solution react with silver nitrate to form silver chloride. Salted collodion acts as an adhesive between glass plates and silver chloride, functioning as a photosensitive layer.

Silver Bath

  The process of immersing a glass plate coated with salted collodion in a silver nitrate solution is called a silver bath. During the silver bath, the following displacement reactions occur between chloride ions and silver nitrate, resulting in the formation of silver chloride:

  -Silver Nitrate + Cadmium Bromide → Silver Bromide + Cadmium Nitrate

  -Silver Nitrate + Potassium Iodide → Silver Iodide + Potassium Nitrate

*Bromide enhances tonal range, while Iodides increase contrast.

  This reaction leads to the formation of silver chloride (silver bromide and silver iodide) within the Collodion. This silver chloride (silver bromide and silver iodide) becomes the photosensitive substance. However, the by-products cadmium nitrate and potassium nitrate can accumulate in the silver nitrate solution and eventually affect image formation negatively, so they need to be periodically removed. The displacement reaction between chloride ions and silver nitrate takes approximately 2 to 4 minutes to complete. As a result, a photosensitive layer containing silver chloride is formed on the glass plate.



  Exposure is done using a camera. The photosensitive layer containing silver chloride is exposed, and in the exposed areas, the silver chloride undergoes a change and is converted into silver particles during the subsequent development process. It should be noted that the sensitivity of the Collodion mixture is around ISO 1.5 for the first month, but after two months, it drops below ISO 1.



  The developer solution typically contains ferrous sulfate and acetic acid. When the developer solution comes into contact with the photosensitive layer, the silver chloride in the exposed areas reacts with ferrous sulfate, transforming into silver particles. Additionally, using a smaller amount of developer solution results in a concentrated silver reaction, producing high-contrast images with bright highlights.


  After development, a fixing solution is used to remove the unexposed (shadow) areas of silver chloride. This process allows only the exposed silver particles to adhere to the glass plate, forming the image. Hypo (sodium thiosulfate) is commonly used for fixing, but some photographers in Europe and America use potassium cyanide. Using potassium cyanide offers the advantage of a warm-toned finish and shorter rinsing time.


  After fixing, whitish spots appear on the image or near the edges of the glass plate. These are excess silver particles that have developed from the unexposed emulsion (silver chloride). It is necessary to carefully remove them using a cotton ball to avoid damaging the emulsion. Rinsing should be performed for at least 20 minutes when using hypo. If using potassium cyanide, rinsing for about 5 minutes is sufficient.


  After rinsing and drying, a coating containing resins such as gum sandarac or water-based varnish is applied. Varnish protects the silver and helps maintain the beauty of the wet plate photograph for a longer period of time.

Wet Plate Photography in Japan

Photography first arrived in Japan in 1848 when daguerreotypes imported from the Netherlands were introduced in Nagasaki. The daguerreotype, a technique perfected by the Frenchman Daguerre, involved applying a silver coating to a copper plate, exposing it to vaporized iodine in a camera, developing it with mercury vapor, and fixing it with sodium thiosulfate (hypo). The daguerreotype technique was publicly disclosed by the French government in 1839, leading to the rapid establishment of photography studios in Europe and the United States. However, records of daguerreotypes in Japan are scarce, with the only known surviving example being the "Statue of Shimazu Nariakira" photographed in the Satsuma domain.

On the other hand, wet plate photography (collodion wet plate process) was invented by Frederick Scott Archer in 1851 in the United Kingdom. It was introduced to Japan around 1854 through the three open ports of Nagasaki, Yokohama, and Hakodate. Since it followed closely after daguerreotypes, wet plate photography is considered the starting point of photography in Japan.

The pioneers of photography in Japan are recognized as Hikoma Ueno and Renjo Shimooka. In 1862, Ueno established a photo studio in Nagasaki, while Shimooka opened one in Yokohama. They played a significant role during the late Edo and Meiji periods, mentoring numerous students. Ueno, influenced by Dutch professor Pompe van Meerdervoort at the Nagasaki Naval Training Center, began experimenting with wet plate photography alongside his disciple, Kuwajiro Horie. Despite facing challenges due to the lack of necessary equipment, Ueno's practical skills improved rapidly after receiving training from the photographer Rosier, who visited Nagasaki. He later obtained a camera for wet plate photography from a Dutch merchant and traveled to Edo to capture photographs of the feudal lord and others. After teaching Dutch and applied chemistry for a while at the domain's school in Tsu, he returned to Nagasaki and established a photography studio at his home.

In contemporary times, the chemicals required for wet plate photography, such as silver nitrate and collodion, can be purchased from chemical suppliers. However, during Ueno's era, these chemicals had to be produced independently. For instance, ammonia was derived from the bones of cattle, and potassium cyanide was obtained from bovine blood. Since eating beef was not a common practice among the Japanese at that time and was considered foreign, Ueno and Horie, under the cover of night, sneaked into a cattle slaughterhouse to acquire the necessary materials. There are also accounts of silver nitrate being created by dissolving Mexican silver coins in nitric acid.

Ueno's studio attracted foreigners and many prominent figures of the late Edo period who visited Nagasaki, with photographs including the famous one of Ryoma Sakamoto. The cost of a photograph in the early Meiji era was around 2 yen for a cabinet-sized print, equivalent to about 40,000 yen in today's value.

In the late 1870s, modern photosensitive materials, such as dry plates, began to be introduced. Unlike wet plate photography, which required on-site development and several seconds of exposure, dry plates were portable and had high sensitivity, significantly transforming the world of photography. Consequently, wet plate photography gradually disappeared from the scene.

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