Gelatin silver process - wikipedia Gelatin silver process This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( September 2008 ) The gelatin silver process is the photographic process used with currently available black - and - white films and printing papers. 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. Contents 1 History 1.1 Timeline 2 Technology 2.1 Overview 2.2 Layer structure 2.3 Image and processing 3 Digital silver gelatin printing 4 In molecular biology 5 References 6 Further reading 7 External links History The gelatin silver process was introduced by Richard Leach Maddox in 1871 with subsequent considerable improvements in sensitivity obtained by Charles Harper Bennett in 1878. Gelatin silver print paper was made as early as 1874 on a commercial basis, but it was poor quality because the dry - plate emulsion was coated onto the paper only as an afterthought. Coating machines for the production of continuous rolls of sensitized paper were in use by the mid-1880s, though widespread adoption of gelatin silver print materials did not occur until the 1890s. The earliest papers had no baryta layer, and it was not until the 1890s that baryta coating became a commercial operation, first in Germany, in 1894, and then taken up by Kodak by 1900. Although the baryta layer plays an important part in the manufacture of smooth and glossy prints, the baryta paper of the 1890s did not produce the lustrous or glossy print surface that became the standard for fine art photography in the twentieth century. Matting agents, textured papers, and thin baryta layers that were not heavily calendering produced a low - gloss and textured appearance. The higher gloss papers first became popular in the 1920s and 30s as photography transitioned from pictorialism into modernism, photojournalism, and `` straight '' photography. Research over the last 125 years has led to current materials that exhibit low grain and high sensitivity to light. Timeline 1874 -- First commercial production of gelatin developing out paper ( DOP ) 1885 -- Coating machines first used in gelatin DOP manufacture for manufacture of continuous rolls 1894 -- Baryta layer added to commercial gelatin DOP manufacture 1920s -- Increasing popularity of glossy and semi-gloss papers 1960s -- Color photography eclipses black and white for the first time Technology Overview The gelatin silver print or gelatin developing out paper ( DOP ) is a monochrome imaging process based on the light sensitivity of silver halides. They have been made for both contact printing and enlarging purposes by modifying the paper 's light sensitivity. A brief exposure to a negative produces a latent image, which is then made visible by a developing agent. The image is then made permanent by treatment in a photographic fixer, which removes the remaining light sensitive silver halides. And finally, a water bath clears the fixer from the print. The final image consists of small particles of silver bound in a layer of gelatin. This gelatin image layer is only one of the four layers found in a typical gelatin silver print, which typically include the overcoat, image layer, baryta, and paper support. Layer structure A gelatin silver print is composed of four layers : paper base, baryta, gelatin binder, and a protective gelatin layer or overcoat. The multi-layer structure of the gelatin silver print and the sensitivity of the silver imaging salts require specialized coating equipment and fastidious manufacturing technique to produce a consistent product that is free of impurities harmful to the image. The paper base or support serves as the substrate onto which the subsequent layers are attached. Paper is in many ways an ideal support : it is lightweight, flexible, and strong enough to withstand both wet processing and regular handling. The photographic paper base must be free of photoactive impurities such as iron and lignins. In order to obtain this purity, the paper was originally made from cotton rags, though after World War I there was a transition to purified wood pulp, which has been used ever since. The second layer is the baryta, a white opaque coating made primarily from gelatin and barium sulfate. Its purpose is to cover the paper fibers and form a smooth surface upon which to coat the gelatin. Surface textures are created by a variety of textured felts used in the drying of the paper, calendaring, and embossing before or after application of the baryta layer depending on the desired effect. The third layer is the gelatin binder that holds the silver grains of the photographic image. Gelatin has many qualities that make it an ideal photographic binder. Among these are toughness and abrasion resistance when dry and its ability to swell and allow the penetration of processing solutions. The fourth layer, called the overcoat, supercoat, or topcoat, is a very thin layer of hardened gelatin that is applied on top of the gelatin binder. It acts as a protective layer, providing superior abrasion resistance to the print surface. Image and processing Before a paper is exposed, the image layer is a clear gelatin matrix holding the light - sensitive silver halides. For gelatin silver prints, these silver halides are typically combinations of silver bromide and silver chloride. Exposure to a negative is typically done with an enlarger, although contact printing was also popular, particularly among amateurs in the early twentieth century and among users of large format cameras. Wherever the light strikes the paper the silver halides form small specks of silver metal on their surface. Light causes a reduction of the silver salt to silver metal. This exposure is the greatest in areas of the print corresponding to clear parts of the negatives, which become the shadows or high density areas of the print. This process is the formation of the latent image, as it forms an invisible image in the paper that is subsequently made visible by development. So the paper is now placed in the developer, which transforms the silver halide particles that have a latent image speck on them into metallic silver. Now the image is visible, but the remaining unexposed silver halide must still be removed to make the image permanent. But first the print is placed into the stop bath, which stops development and prevents the developer from contaminating the next bath : the fixer. The fixer, typically sodium thiosulfate, is able to remove the unexposed silver halide by forming a water - soluble complex with it. And finally, a water wash sometimes preceded by a washing aid removes the fixer from the print, leaving an image composed of silver particles held in the clear gelatin image layer. Toning is sometimes used for permanence or aesthetic purposes and follows the fixing step. Selenium, gold, and sulfur toners are the most common and act by either partially converting the silver to another compound ( such as silver selenide or silver sulfide ) or partially replacing the silver with another metal ( such as gold ). 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. Digital silver gelatin printing Also known as digital bromides, black and white silver gelatin prints imaged via digital output devices such as the Durst Lambda and the Océ LightJet, have been developed for the art market by Ilford Imaging -- now Harman Technology in collaboration with Steve McLeod. By adapting a large format paper processor in conjunction with the manufacturers, McLeod 's innovation led the way for the possibility of producing large resin coated ( RC ) and fibre based ( FB ) black and white prints. Ilford, in collaboration with Metro Imaging, London adapted their FB Galerie emulsion paper and its light sensitivity so that it would be receptive to full spectrum RGB laser channels. In molecular biology An essentially identical procedure called `` silver staining '' is utilized in molecular biology to visualize DNA or proteins after gel electrophoresis, usually SDS - PAGE. The latent image is formed by the DNA or protein molecules ( i.e. the reduced silver selectively precipitates onto those molecules ). It is known for being nearly as sensitive as autoradiography, the `` gold standard '' technique, but one not widely used due to the use of radioactive materials. References ^ Jump up to : Weaver, Gawain ( 2008 ). `` A Guide to Fiber - Base Gelatin Silver Print Condition and Deterioration '' ( PDF ). George Eastman House, International Museum of Photography and Film. Retrieved 30 October 2009. Jump up ^ Bassam, Brant J ( 25 October 2007 ). `` Silver staining DNA in polyacrylamide gels '' ( PDF ). Nature Protocols. 2 : 2649 -- 2654. doi : 10.1038 / nprot. 2007.330. Retrieved 5 October 2015. Further reading Adams, Ansel ( 1950 ). The print : Contact printing and enlarging ( 2 ed. ). Boston : New York Graphic Society. ISBN 0821207180. Eaton, G.T. ( 1965 ). Photographic chemistry in black - and - white and color photography. Hastings - on - Hudson, N.Y., : Morgan & Morgan. Gray, G.G. ( 1987 ). From Papyrus to RC Paper : History of Paper Supports. Pioneers of Photography : Their Achievements in Science and Technology. E. Ostroff. Springfield, VA, : The Society for Imaging Science and Technology : 37 - 46. Jacobson, Ralph E. ( 2000 ). The manual of photography : photographic and digital imaging ( 9th ed. ). Boston, Mass. : Focal Press. ISBN 0240515749. Rogers, David ( 2007 ). The chemistry of photography : from classical to digital technologies. Cambridge : RSC Publ. ISBN 0 - 85404 - 273 - 3. Weaver, G. ( 2008 ) A Guide to Fiber - Base Gelatin Silver Print Condition and Deterioration. George Eastman House, International Museum of Photography and Film. Wentzel, F. and L.W. Sipley ( 1960 ). Memoirs of a photochemist. Philadelphia : American Museum of Photography. External links Notes on Photographs @ George Eastman House Graphics Atlas @ Image Permanence Institute Mark Scholer Pedersen. `` Silver gelatin dry plate process ''. alternative photography.com. Retrieved 2017 - 08 - 30. Photography Outline Terminology 35 mm equivalent focal length Angle of view Aperture Black and white Chromatic aberration Circle of confusion Color balance Color temperature Depth of field Depth of focus Exposure Exposure compensation Exposure value Zebra patterning F - number Film format Large Medium Film speed Focal length Guide number Hyperfocal distance Metering mode Orb ( optics ) Perspective distortion Photograph Photographic printing Photographic processes Reciprocity Red - eye effect Science of photography Shutter speed Sync Zone System Genres Abstract Aerial Architectural Astrophotography Banquet Conceptual Conservation Cloudscape Documentary Ethnographic Erotic Fashion Fine - art Fire Forensic Glamour High - speed Landscape Lomography Nature Neues Sehen Nude Photojournalism Pornography Portrait Post-mortem Selfie Social documentary Sports Still life Stock Street Vernacular Underwater Wedding Wildlife Techniques Afocal Bokeh Brenizer Burst mode Contre - jour Cyanotype ETTR Fill flash Fireworks Harris shutter HDRI High - speed Holography Infrared Intentional camera movement Kirlian Kite aerial Long - exposure Macro Mordançage Multiple exposure Night Panning Panoramic Photogram Print toning Redscale Rephotography Rollout Scanography Schlieren photography Sabatier effect Stereoscopy Stopping down Strip Slit - scan Sun printing Tilt -- shift Miniature faking Time - lapse Ultraviolet Vignetting Xerography Composition Diagonal method Framing Headroom Lead room Rule of thirds Simplicity Equipment Camera light - field field instant pinhole press rangefinder SLR still TLR toy view Darkroom enlarger safelight Film base format holder stock Filter Flash beauty dish cucoloris gobo hood hot shoe monolight Reflector snoot Softbox Lens Wide - angle lens Zoom lens Telephoto lens Manufacturers Monopod Movie projector Slide projector Tripod head Zone plate History Timeline of photography technology Analog photography Autochrome Lumière Box camera Calotype Camera obscura Daguerreotype Dufaycolor Heliography Painted photography backdrops Photography and the law Glass plate Visual arts Digital photography Digital camera D - SLR comparison MILC camera back Digiscoping Digital versus film photography Film scanner Image sensor CMOS APS CCD Three - CCD camera Foveon X3 sensor Image sharing Pixel Color photography Color Print film Reversal film Color management color space primary color CMYK color model RGB color model Photographic processing Bleach bypass C - 41 process Cross processing Developer Digital image processing Dye coupler E-6 process Fixer Gelatin silver process Gum printing Instant film K - 14 process Print permanence Push processing Stop bath Lists Most expensive photographs Photographers Norwegian Polish street women Portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Gelatin_silver_process&oldid=804971906 '' Categories : Photographic processes dating from the 19th century Gelatin Hidden categories : Articles needing additional references from September 2008 All articles needing additional references Talk Contents About Wikipedia Magyar Nederlands Polski Português Русский Svenska Edit links This page was last edited on 12 October 2017, at 07 : 15. 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Question: where did the dry plate (gelatin-silver) system originate
Answer: 1871