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A bleachfield or bleaching green was an open area used for spreading cloth on the ground to be purified and whitened by the action of the sunlight. [1] Bleaching fields were usually found in and around mill towns in Great Britain and were an integral part of textile manufacture during the British Industrial Revolution .
Development of more biodegradable alternatives to the EDTA and other bleaching agent constituents were sought by major manufacturers, until the industry became less profitable when the digital era began. In most amateur darkrooms, a popular bleach is potassium ferricyanide. This compound decomposes in the waste water stream to liberate cyanide gas.
In photography, toning is a method of altering the color of black-and-white photographs. In analog photography, it is a chemical process carried out on metal salt-based prints, such as silver prints, iron-based prints (cyanotype or Van Dyke brown), or platinum or palladium prints. This darkroom process cannot be performed with a color photograph.
Next, the film goes into the pre-bleach (formerly conditioner) bath, which has a precursor of formaldehyde (as a dye preservative) and EDTA to "kick off" the bleach. Next, the film goes into a bleach solution. The bleach converts metallic silver into silver bromide, which is converted to soluble silver compounds in the fixer.
The pre-bleach bath relies on carry-over of the color developer to function properly, therefore there is no wash step between the color developer and pre-bleach baths. [5] 6 Bleach bath Bath 5 6: 92–103 °F (33.3–39.4 °C) This is a process-to-completion step, and relies on carry-over of pre-bleach to initiate the bleach.
Dye destruction or dye bleach is a photographic printing process, in which dyes embedded in the paper are bleached (destroyed) in processing. [1] Because the dyes are fully formed in the paper prior to processing, they may be formulated with few constraints, compared to the complex dye couplers that must react in chromogenic processing.
Photobleaching: The movie shows photobleaching of a fluorosphere. The movie is accelerated, the whole process happened during 4 minutes. In optics, photobleaching (sometimes termed fading) is the photochemical alteration of a dye or a fluorophore molecule such that it is permanently unable to fluoresce.
Bleach bypass, also known as skip bleach or silver retention, is a chemical effect which entails either the partial or complete skipping of the bleaching function during the processing of a color film. By doing this, the silver is retained in the emulsion along with the color dyes. The result is a black-and-white image over a color image.