Bad preservation! evaluation afternoon ,,,

storage

Morning work in afternoon thermal bath

Relaxing in Gallery

sea/son ... the SEASON

,,, thousands of projects in many contexts,

In these Easter cleaning between books magazines and papers photographs would

deepen a technique photography much used but little known ...

" Silver gelatin DOP "

Silver gelatin DOP is based on the light sensitivity of silver halides, which are suspended in a gelatin binder on a baryta paper support. DOPs made their first appearance in the mid 1880s and became the dominate printing process of the twentieth century. Due to the complexity of the process, silver gelatin papers have always been a manufactured product. As chemists’ understanding of silver halide chemistry increased over time, papers could be manufactured with a variety of characteristics, including varying light sensitivities, speeds, and tonal ranges. Papers were also produced with a variety of surface sheens, textures, paper thickness and paper tints. Optical brightening agents were introduced to papers beginning in the 1960s, which serve to make the highlights brighter providing papers with more contrast.

"Silver gelatin DOPs have a paper support. Most prints made before 1970 have fiber-based paper supports of varying paper weights. The standard weights are described by manufacturers in different ways including: heavy, medium, and light weight; single-weight, double weight, lightweight, extra thin. Water-resistant papers coated with cellulose acetate were made before the late 1960s. These papers were used in photo booths, as ID pictures, and for printing map reproductions, among other things that required fast processing. In the late 1960s papers coated with polyethylene, called resin-coated (RC) papers, were introduced. RC papers are coated on the back with clear polyethylene and on the front, directly below the emulsion, with pigmented polyethylene and are easily identified by their smooth plastic back. Specialty metallic papers were marketed until the 1970s. These have a special surface that give the print a metallic appearance". 

Significant advancements were made throughout the twentieth century to silver gelatin emulsion making for both negative and print materials. During manufacturing of the emulsion, silver nitrate is combined with a halide (usually a combination of bromide and chloride, though silver iodide papers were also made) in the presence of gelatin with an excess of halide present. The gelatin slows the formation of the crystals allowing for smaller, more uniform crystals to form and react with impurities (sulfur) in the gelatin, all of which make the silver halide crystals more light sensitive. The emulsion is then heated in a process called Ostwald Ripening which increases silver halide sensitivity and creates more uniform silver halide crystals. The next step is to remove impurities from the gelatin. Initially emulsions were shredded into noodles, washed to remove impurities, and then heated and re-melted. Later emulsion making required a complicated procedure of flocculation which required altering the pH of the emulsion causing the silver halides to precipitate out. The silver halides were washed and dispersed back into the emulsion. Another way of extracting impurities is through reverse osmosis through a thin membrane. Finally additional sensitizing chemicals and other additives are added. Gelatin is the perfect binder for silver halide crystals; it has the ability to swell allowing the penetration of processing solutions, but is tough and resistant to abrasions when dry. The gelatin emulsion was then machine coated onto a baryta paper support.

 A final thin layer of hardened gelatin was applied to act as a protective layer called an overcoat, also called a supercoat or topcoat.

DOPs can be contact printed or printed by enlargement through a negative. During exposure, a latent image is formed where light strikes the paper. Development reduces the silver ions in the latent image to visible silver particles in an oxidation-reduction reaction. Development is followed by a stop bath, which halts development and keeps the following fixing bath from being contaminated with developing solution. Next, unexposed silver halides are removed in a fixing solution, usually sodium thiosulfate, which dissolves silver halide crystals into a water soluble compound. Finally the print is washed thoroughly to remove residual processing chemicals and by products produced during fixing.

Photographers may choose to tone prints to alter the image color and/or to increase the stability of the print. Popular toners include gold, polysulfides, and selenium or a combination of sulfide and selenium.  Gold toning replaces part of the silver image with a more noble metal (gold). Gold toning usually produces a cooler neutral image tone of blue-black. Selenium and sulfide toners create a compound with silver that is more stable than silver alone. Image tones generally range from sepia, brown, purple, and purple-brown. This can be done by indirect toning in which after fixing the silver image is bleached and then immersed in the toning solution. The sulfide solution reacts with the silver halides to form silver sulfide. Direct toning does not require bleaching. Dye toning converts the silver image to a dye mordant that attracts dye from a dye solution. Finally, metal ferricyanide toning converts the silver image into silver ferricyanide complex which is then converted to a ferricyanide salt of a different metal (iron, copper, uranium). Dye toning and metal ferricyanide toning can result in a diverse rainbow of image colors.

Victorian mood ---

• The History of Photographic Printing in the 19th Century
• The Component Materials of 19th-Century Prints and Their Forms of Deterioration
• Stability of Specific Print Materials
• Identification of 19th-Century Photographic and Photomechanical Print Processes
• Preservation and Collection Management
• Storage        
• 
  

the allure of train travel OVVERO the circle is perfect?

(...) the fascination of reading on the train...landscape and reflections/perplexity ...

a new project.

Popular photography can properly be said to have started 120 years ago with the introduction of the Kodak camera, the invention of an American, George Eastman (1854-1932). It was a simple, leather-covered wooden box – small and light enough to be held in the hands. Taking a photograph with the Kodak was very easy, requiring only three simple actions; turning the key (to wind on the film); pulling the string (to set the shutter); and pressing the button (to take the photograph). There wasn’t even a viewfinder – the camera was simply pointed in the direction of the subject to be photographed. The Kodak produced circular snapshots, two and a half inches in diameter. The Kodak was sold already loaded with enough paper-based roll film to take one hundred photographs. After the film had been exposed, the entire camera was returned to the factory for the film to be developed and printed. The camera, reloaded with fresh film, was then returned to its owner, together with a set of prints. To sum up the Kodak system, Eastman devised the brilliantly simple sales slogan: ‘You press the button, we do the rest.’

p.s. In the late-sixties Emmet Gowin gave the circle another shot. In his 1976 monograph, Photographs, he writes:

About the circular pictures: I had quite forgotten that it was the nature of the lens to form a circle and in 1967 my only lens was a short Angulon intended for a small camera. I’d been given an old Eastman View 8×10 and brought the two together out of impatience and curiosity. After a while, I recognized the wonderful exaggeration near the edge. I began to use the camera with the lens, but for several years I would trim these prints so that the circle was disguised. Eventually I realized that such a lens contributed to a particular description of space and that the circle itself was already a powerful form.

Accepting the entire circle, what the camera had made, was important to me. It involved recognition of the inherent nature of things. I had set out to describe the world with my domain, to live a quality with things. Enrichment, I saw, involves a willingness to accept a changing vision of the nature of things – which is to say, reality. Often I had thought that things teach me what to do. Now I would prefer to say: As things reach us what we already are, we gain a vision of the world.