Platinotype
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2008-06-21T22:02:05Z
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'''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]]