Platinum prints, also called platinotypes, are photographic prints made by a monochrome printing process that provides the greatest tonal range of any printing method using chemical development. Platinum prints are made by photographers and favored by collectors because of their tonal range, the surface quality and their permanence. A platinum print provides a broad scale of tones from black to white. The platinum tones range from warm black, to reddish brown, to expanded mid-tone grays that are unobtainable in silver prints. Unlike the silver print process, platinum lies on the paper surface, while silver lies in a gelatin or albumen emulsion that coats the paper. As a result, since no gelatin emulsion is used, the final platinum image is absolutely matte with a deposit of platinum (and/or palladium, its sister element which is also used in most platinum photographs) absorbed slightly into the paper. Platinum prints are the most durable of all photographic processes. The platinum group metals are very stable against chemical reactions that might degrade the print—even more stable than gold. It is estimated that a platinum image, properly made, can last thousands of years. Some of the desirable characteristics of a platinum print include: The reflective quality of the print is much more diffuse in nature compared to glossy prints that typically have specular reflections. A very delicate, large tonal range. Not being coated with gelatin, the prints do not exhibit the tendency to curl. The darkest possible tones in the prints are lighter than silver-based prints. Recent studies have attributed this to an optical illusion produced by the gelatin coating on RC and fiber-based papers. However, platinotypes that have been waxed or varnished will produce images that appear to have greater D-max than silver prints. A greatly decreased susceptibility to deterioration compared to silver-based prints due to the inherent stability of the process and also because they are commonly printed on 100% rag papers. Many practitioners have abandoned platinum and only use palladium. The process using palladium alone (sodium tetrachloropalladate) is similar to standard processes, but rather than using ferric oxalate plus potassium chlorate as the restrainer (which is ineffective for palladium), a weak solution of sodium chloroplatinate is used instead. Sodium chloroplatinate, in contrast to potassium chlorate, does not cause grain. This formula is generally referred to as the Na2 method. This somewhat misleading abbreviation was coined by Richard Sullivan of Bostick & Sullivan, one of the principal suppliers of chemistry and printing supplies, who popularized the process.
Cyanotype is a photographic printing process that produces a cyan-blue print. Engineers used the process well into the 20th century as a simple and low-cost process to produce copies of drawings, referred to as blueprints. The process uses two chemicals: ammonium iron(III) citrate and potassium ferricyanide. In a typical procedure, equal volumes of an 8.1% (w/v) solution of potassium ferricyanide and a 20% solution of ferric ammonium citrate are mixed. This mildly photosensitive solution is then applied to a receptive surface (such as paper or cloth) and allowed to dry in a dark place. Cyanotypes can be printed on any surface capable of soaking up the iron solution. Although watercolor paper is a preferred medium, cotton, wool and even gelatin sizing on nonporous surfaces have been used. Care should be taken to avoid alkaline-buffered papers, which degrade the image over time. A positive image can be produced by exposing it to a source of ultraviolet light (such as sunlight) through a contact negative (which can be produced by any suitable means, e.g. a conventional photographic negative or a print on acetate film made using photo-processing software to invert a positive monochrome digital image). The UV light reduces the iron(III) to iron(II). This is followed by a complex reaction of the iron(II) complex with ferricyanide. The result is an insoluble, blue dye (ferric ferrocyanide) known as Prussian blue. Exposure to ultraviolet light reduces the iron in the exposed, turning the paper a steel-grey-blue color. The extent of color change depends on the amount of UV light, but acceptable results are usually obtained after 10–20 minute exposures on a dark, gloomy day. The highlight values should appear overexposed, as the water wash reduces the final print values. Prints can be made with large format negatives and lithography film, or everyday objects can be used to makephotograms. After exposure, developing of the picture involves the yellow unreacted iron solution being rinsed off with running water. Although the blue color darkens upon drying, the effect can be accelerated by soaking the print in a 6% (v/v) solution of 3% (household) hydrogen peroxide. The water-soluble iron(III) salts are washed away, while the non-water-soluble Prussian blue remains in the paper. This is what gives the picture its typical blue color. The overall contrast of the sensitizer solution can be increased with the addition of approximately 6 drops of 1% (w/v) solution potassium dichromate for every 2 ml of sensitizer solution.
The gelatin silver process is the photographic process used with currently available black-and-white films and printing papers. This is one of the many ways of producing a photograph. A suspension of silver salts in gelatin is coated onto a support such as glass, flexible plastic or film, baryta paper, or resin-coated paper. These light-sensitive materials are stable under normal keeping conditions and are able to be exposed and processed even many years after their manufacture. This is in contrast to the collodion wet-plate process dominant from the 1850s–1880s, which had to be exposed and developed immediately after coating. The gelatin silver process was introduced by Richard Leach Maddox in 1871 with subsequent considerable improvements in sensitivity obtained by Charles Harper Bennet in 1878. Research over the last 125 years has led to current materials that exhibit low grain and high sensitivity to light. When small crystals (called grains) of silver salts such as silver bromide and silver chloride are exposed to light, a few atoms of free metallic silver are liberated. These free silver atoms form the latent image. This latent image is relatively stable and will persist for some months without degradation provided the film is kept dark and cool. Films are developed using solutions that reduce silver halides in the presence of free silver atoms. An 'amplification' of the latent image occurs as the silver halides near the free silver atom are reduced to metallic silver. The strength, temperature and time for which the developer is allowed to act allow the photographer to control the contrast of the final image. The development is then stopped by neutralizing the developer in a second bath. Once development is complete, the undeveloped silver salts must be removed by fixing in sodium thiosulphate or ammonium thiosulphate, and then the negative or print must be washed in clean water. The final image consists of metallic silver embedded in the gelatin coating. All gelatin silver photographic materials are subject to deterioration. The silver particles that comprise the image are susceptible to oxidation, leading to yellowing and fading of the image. Poor processing can also result in various forms of image degradation, due to residual silver-thiosulfate complexes. Toning increases the stability of the silver image by coating the silver image with a less easily oxidized metal such as gold, or by converting portions of the silver image particles into more stable compounds, such as silver selenide or silver sulfide. Gelatin silver printing was the dominant photographic process from introduction in the 1880s until the 1960s when it was eclipsed by consumer color photography. The gelatin silver or black-and-white print is thus a primary form of visual documentation in the 20th century. Its widespread use in applications as wide-ranging as fine art, snap shots, and document reproduction led to an extraordinary variety of papers with a wide range of available surface texture and gloss, and paper thickness.
Van Dyke Brown is an early photographic printing process. The process was so named due to the similarity of the print color to that of a brown oil paint named for Flemish painter Anthony van Dyck.
The solution is made out of a mix of three different solutions.
Solution 1:Dissolve 10 grams ferric ammonium citrate in 30 ml distilled water.
Solution 2: Dissolve 1.5 grams tartaric acid in 30 ml distilled water.
Solution 3: Dissolve 4 grams silver nitrate in 30 ml distilled water.
Combine the 3 solutions and stir well. Add enough distilled water to make 100 ml of solution. The solution will keep for several weeks if stored in a cool, dark place.
Printing with Van Dyke Brown requires the use of a large format negative in the size of the desired print, a suitable substrate for coating and subsequent printing, and an ultraviolet light source, either sunlight or suitable bulbs. The substrate can be almost anything to which the solution will adhere. Watercolor paper is a good first choice, but trickier substrates such as metal, glass, or tile can be first 'sized' with gelatin or arrowroot to facilitate coating. The substrate is coated with solution under tungsten light, air-dried, and coated a second time, if desired, for a stronger image. The negative is placed on the thoroughly dried coated substrate, and is then weighted with a piece of glass. Frequent printers often use a printing frame to ease the checking of printing progress without disturbing the registration, or alignment, of the negative on the paper. These printing frames also ease the printing of a second coat over the same image. The glass-negative-substrate 'sandwich' is exposed to a source of UV light. UV bulbs offer more control and consistency of light than sunlight, but at greatly increased cost. Standard daylight fluorescents produce some UV light, but printing times may be very long. A good starting point for printing time is to check a region of your photo that is very light but should still show some tone or detail (a highlight), and note how long it takes to register this detail, and print as long again. The latent image now appears, although flat and lacking substantial shadow tones. The image must now be washed, or cleared, in several changes of water to remove soluble iron and silver compounds. It is good practice to slightly acidify the wash water, as iron compounds are more soluble in acid. A pinch of citric acid, dab of vinegar or pineapple juice will do the trick. As the image soaks, white cloudy precipitate of silver chloride will appear from the reaction of silver nitrate with chlorine in the water. Continue to wash for a few changes of water after this cloudiness ceases to appear. Fixing is best done with a weak, alkaline fixer of 5% sodium thiosulfate with a teaspoon of household ammonia per liter. The alkali slows the fixing process and prevents rapid bleaching of the image. Almost immediately, the tones of the image will change to a deep chocolate brown. Keep fixing until the whites appear clear; about 2 minutes, and finish with a second, clean fix if desired for thorough removal of salts that would fade the image. Use a fixer clearing bath of sodium sulfite to help remove residual fixer, and give the print an extended wash fitting the absorbency of the substrate, around 30–45 minutes for absorbent papers, or 5–10 minutes for gelatin-sized tile or glass. Air dry the print without heat. High heat will change the color of the print to more neutral and weaken the shadows.
The collodion process is an early photographic process, invented by Frederick Scott Archer. It was introduced in the 1850s and by the end of that decade it had almost entirely replaced the first practical photographic process, the daguerreotype. During the 1880s the collodion process, in turn, was largely replaced by gelatin dry plates—glass plates with a photographic emulsion of silver halides suspended in gelatin. The dry gelatin emulsion was not only more convenient but could be made much more sensitive, greatly reducing exposure times. "Collodion process" is usually taken to be synonymous with the "collodion wet plate process", a very inconvenient form which required the photographic material to be coated, sensitized, exposed and developed within the span of about fifteen minutes, necessitating a portable darkroom for use in the field. Although collodion was normally used in this wet form, the material could also be used in humid ("preserved") or dry form, but at the cost of greatly increased exposure time, making these forms unsuitable for the usual work of most professional photographers—portraiture. Their use was therefore confined to landscape photography and other special applications where minutes-long exposure times were tolerable. Collodion processes were capable of recording microscopically fine detail, so their use for some special purposes continued long after the advent of the gelatin dry plate. The wet plate collodion process was still in use in the printing industry in the 1960s for line and tone work (mostly printed material involving black type against a white background) as for large work it was much cheaper than gelatin film. One collodion process, the tintype, was still in limited use for casual portraiture by some itinerant and amusement park photographers as late as the 1930s, by which time tintypes were already regarded as quaintly old-fashioned. The collodion process is said to have been invented, almost simultaneously, by Frederick Scott Archer and Gustave Le Gray in about 1850. During the subsequent decades of its popularity, many photographers and experimenters refined or varied the process.
Gumoil prints, such as the one adjacent to this paragraph, were so named by Karl Koenig in his first book published in 1994 by Focal Press. The term is a composite of Oil Pigments and Gum Arabic (mixed with potassium bichromate for its UV sensitivity) . Using photographic positives Gumoil is a versatile, but labor intensive process which can yield painterly images on cold press paper or more photographic results if hot press paper is used. No two prints are ever truly identical and when numbered in a series they are captioned as “edition variable.”
Gum bichromate is a 19th-century photographic printing process based on the light sensitivity of dichromates. It is capable of rendering painterly images from photographic negatives. Gum printing is traditionally a multi-layered printing process, but satisfactory results may be obtained from a single pass. Any color can be used for gum printing, so natural-color photographs are also possible by using this technique in layers.
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