Platinotype 870979 220845327 2008-06-21T22:02:05Z DOI bot 6652755 Citation maintenance. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. '''Platinotype''' is a [[monochrome]] [[photographic printing]] process, based on the [[Photophobia|light-sensitivity]] of [[ferric]] [[oxalate]]. Ferric oxalate is reduced to [[Iron(III) oxalate|ferrous oxalate]] by [[UV-light]]. The ferrous oxalate then reacts with [[platinum]] (II) (or [[palladium]] II) reducing it to basic platinum, which builds up the image. [[William Willis (inventor) | William Willis]] discovered the process in [[1873]] and the first platinum paper reached the market in [[1881]], produced by the Platinotype Company, a firm founded by Willis in [[1879]]. When Willis invented the process, platinum was relatively cheap, but it quickly became more costly starting in [[1906]]. In [[1907]] platinum had become 52 times more expensive than [[silver]]. [[Eastman Kodak]] and most other producers stopped fabrication of the paper in [[1916]]. [[Russia]] controlled 90% of the world platinum supply in [[World War I]] and all available platinum was used in the war effort. Due to the shortage of commercial paper and high cost, photographers experimented with palladium paper and platinum-palladium mixes. Platinum paper has continued in use until the present, interrupted only by the world wars. Due to the unavailability of pre-coated sensitized paper, all [[platinum]]/[[palladium]] (Pt/Pd) printing is done on paper coated by the printer. The light sensitive chemicals are mixed from powdered basic chemicals, or some commercially available solutions, then hand applied with a brush or a cylindrical "pusher". Many artists achieve varying effects by choosing different papers for different surface characteristics, including [[vellum]], rag, rice, among others - even silk. On the collecting market, Pt/Pd photographic prints often sell for many times what a similar silver-gelatin print would sell for. By varying the amount of Pt vs Pd and the addition of oxidizing chemicals such as [[hydrogen peroxide]] and [[potassium dichromate]] or [[potassium chlorate]], the contrast and "colour" of the final image can be modified. Because of the non-uniformity of the coating and mixing phases of the process, no two prints are exactly the same, adding additional "cachet" to a Pt/Pd print. The inherent low sensitivity of the process is because the ferric oxalate is sensitive to [[ultra-violet light]] only, thus specialized light sources must be used and exposure times are many times greater than those used in silver-based photographic processes. == Characteristics == * An absolutely non-reflective surface of the prints, compared to modern-day glossy prints * Very delicate, large tonal range * The prints, not being coated with [[gelatin]], do not exhibit the tendency to curl * The darkest possible tones in the prints are still lighter than silver-based prints. Recent studies have this attributed to an optical illusion produced by the gelatin coating on RC and fibre-based papers. Platinotypes which have been waxed or varnished will produce images that appear to have greater [[D-max]] than silver prints. * Very stable process, platinum prints are far less susceptible to deterioration than silver-based prints because they are commonly printed on 100% rag papers ==See also== * [[Palladiotype]] * [[Photographic processes]] ==References== * {{cite journal | author= Mike Ware | title = An Investigation of. Platinum and Palladium Printing | journal = Journal of Photographic Science | year = 1986 | volume = 34 | issue = 5-6 | pages = 165–177 | url = http://www.mikeware.co.uk/downloads/Palladium_Printing.doc }} * {{cite journal | author = Mike Ware | title = Book Review of : Photography in Platinum and Palladium | journal = Platinum Metals Review | volume = 49 | issue = 4 | pages = 190–195 | year = 2005 | doi = 10.1595/147106705X70291}} == External links == * [http://www.platinotype.com/ platinotype.com]: A Platinum/Palladium Printing Service * [http://www.contactprintersguild.com/ contactprintersguild.com]: Fine-art contact prints in platinum/palladium and other processes {{photography-stub}} [[Category:Photographic processes]] [[ru:Платиновая печать]]