In film developing, photographic developer (or just developer) is a chemical that makes the image on the film or print visible. A piece of photographic film that has been exposed to light in a controlled manner must be developed before it can be used. ...

Formulae

For black and white photography, the developer is often a mixture of metol and hydroquinone. These are made up in aqueous solution with sodium carbonate to create the appropriately high pH and sodium sulphite to provide strong reducing conditions to delay oxidation of the developing agents by atmospheric oxygen. ... Benzenediols or dihydroxybenzenes are aromatic chemical compounds in which two hydroxyl groups are substituted onto a benzene ring. ... Sodium carbonate or soda ash, Na2CO3, is a sodium salt of carbonic acid. ... pH is a measure of the activity of hydrogen ions (H+) in a solution and, therefore, its acidity or alkalinity. ... In chemistry, sodium sulfite is a soluble compound of sodium. ... General Name, Symbol, Number Oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16 (VIA), 2, p Density, Hardness 1. ...

Most developers also contain small amounts of potassium bromide to modify and restrain the action of the developer to enable penetration of the developer throughout the emulsion before over-development occurs on the surface - chemical fogging. This also changes the colour of the silver image from sepia (low bromide) through black to blue (high bromide). Developers for high contrast work have higher concerntrations of Metol and lower concentrations of Hydroquinone and tend to use strong alkalis such as Potassium carbonate to push the pH up to around pH14. Potassium bromide (KBr) is a salt, used as an anticonvulsant and a sedative in the 1800s. ... For the battery, see alkaline battery The word alkali can mean:- In chemistry, an alkali is a specific type of base, formed as a carbonate, hydroxide or other ionic salt of an alkali metal or alkali earth metal element. ... Potassium carbonate (also known as pearl ash or salts of tartar) is a white salt soluble in water which forms a strongly alkaline solution. ...

Because Metol is difficult to dissolve in solutions of sodium sulphite it is important to dissolve a very small measure of sodium sulphite in water together with the sodium carbonate before adding the Metol and only add the remaining sodium sulphite once all the Metol has been dissolved. Other modern constituents include small amounts of wetting agents and small amounts of alcohol, often propanol In general usage, alcohol (from Arabic al-khwl الكحول, or al-ghawl الغول) refers almost always to ethanol, also known as grain alcohol, and often to any beverage that contains ethanol (see alcoholic beverage). ... Propanol, sometimes known as 1-propyl alcohol, is a higher alcohol with a three carbon atoms and a general formula of C3H7OH of the form: H H H | | | H - C - C - C - OH | | | H H H Propanol boils at 97,1 C There is an another isomer of this compound...

In the early days of photography, a wide range of developing agents were used includings ferrous oxalate, hydroxylamine, lactate of iron, ferrous citrate, Eikonogen, atchecin, resorcin, antipyrin , acetanilid and Amidol {which unusually required midly acidic conditions) The compound hydroxylamine is a nitrogen-containing base whose chemical formula is NH2OH, and is therefore a close relative of the compound ammonia. ... Resorcin (meta-dioxybenzene), C5H4(OH)2, one of the dihydric phenols. ... Phenazone is an analgesics. ... Acetanilide is odorless substance in a leaflet or flake form. ...

Other constituents of developers in the past have included ammonia, glycerine sulphuric acid , sulphurous acid , potassium ferricyanide, potassium oxalate , citric acid and methanol. Ammonia is a chemical compound with the formula NH3. ... Glycerin, also known as glycerine and glycerol, and less commonly as 1,2,3-propanetriol, 1,2,3-trihydroxypropane, glyceritol, and glycyl alcohol is a colorless, odorless, hygroscopic, and sweet tasting viscous liquid. ... Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ... Sulfurous acid (British English: Sulphurous), also known as sulfur dioxide solution, H2SO3, is a mineral acid (not an organic acid), formed when sulfur dioxide dissolves in water. ... Potassium ferricyanide (K3Fe(CN)6), also known as Red prussiate or Prussian Red, is a coordination compound that is stable at room temperature and pressure and forms ruby red crystals and powder. ... Citric acid is a weak organic acid found in citrus fruits. ... Methanol, also known as methyl alcohol or wood alcohol, is a chemical compound with chemical formula CH3OH. It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid that is used as an antifreeze, solvent, fuel, and as a denaturant for ethyl alcohol. ...

Development

The developer reduces the silver halides in the latent image in the exposed photograph into reduced, opaque, black silver metal. The image is then fixed using photographic fixer. A silver halide is one of the compounds formed between silver and one of the halogens, notably silver bromide (AgBr), silver chloride (AgCl) and silver iodide (AgI). ... In photography a latent image is formed when light (or in radiography, X-rays) acts on a photographic emulsion. ... General Name, Symbol, Number silver, Ag, 47 Chemical series Transition metals Group, Period, Block 11, 5, d Density, Hardness 10490 kg/m3, 2. ... Photographic fixer is a chemical used in the final step in black and white film or paper development. ...

The mechanism by which this reduction occurs preferentially on those halide grains containing the silver atoms of the latent image is complex. The developer molecule (typical a relatively simple benzene-ring molecule) may act as an 'electron bridge' - see say www.kodak.com for detailed explanations.

Colour development

In colour and chromogenic black and white photography, a similar development process is used except that the reducing silver catalyses the production of dye-stuffs in the emulsion. There are three distinct processes used here. The C41 process is used for almost all colour negative films and in this process dye couplers in the emulsion react with dye formers in the developer to generate the visible dyes. An almost identical process is then used to produce colour prints from films. The developing agents used are however identical to those used in black and white films. A catalyst (Greek: καταλύτης, catalytis) is a substance that accelerates the rate of a chemical reaction, at some temperature, but without itself being transformed or consumed by the reaction (see also catalysis). ... C-41 is the name given to the process for developing a specific type of color film used in photography and often to the type of film itself. ...

Reversal film development

In many colour transparencies, the film is first processed in a sophisticated black and white developer and is then treated with a 'reversal chemical which stops the initial development and converts the previously unexposed silver into the new latent image. The film is developed again using a process similar to C41 before final fixing and washing. The most common processing chemistry for such films is E6, derived from a long line of developers produced for the Ektachrome range of films. The E-6 process (sometimes abbreviated to just E-6) is a process for developing color reversal (transparency) photographic film. ... Ektachrome films produced by Kodak and available in most formats including 35mm. ...

Proprietary methods

The Kodachrome process is a proprietary process in which all the dyes are added to the emulsion during development. This article is about the color film. ...

In colour print development, the Cibachrome process also uses a print material with the dye-stuffs present and which are bleached out in a appropriate places during developing. The chemistry involved here is wholly different from C41 chemistry.