Film Fixers

The fixer came a lot later than the developer. The first attempts to use the blackening of silver salts by light in any sort of artistic manner date back to the early eighteenth century but the developer did not begin to make an appearance until Daguerre used mercury vapour to make a latent image visible. In the meantime, various pictures had been produced but attempts to make the image permanent had not met with much success. The main function of the fixing solution is to facilitate the removal from the emulsion of silver halides that have not been affected by light. If they are not removed they will eventually blacken and obscure the image. The manner in which the fixer accomplishes this task is not a simple one. It converts the halides into soluble silver compounds but the conversion is a two-stage process. The first stage produces a compound that is barely soluble and is also unstable. Only after that stage is passed are the complex soluble compounds formed that can eventually be removed by washing. The capacity of a fixing solution is very difficult to determine. It is evident that the more work it has to do, the sooner the fixer is exhausted. That may account for the recommendation by one authority in the 1950s that for an eight-exposure spool, at least 60 oz of fixer should be used and then discarded. The pH should be around 4.2 to 4.6. If it is higher than 4.6 an appropriate quantity of acetic acid could be added but when working with small quantities it is more practicable to discard it.

Developers for Contrast Control

The developers mentioned so far are used in general photography of subjects in reasonable lighting and with a normal distribution of tones. There are other forms of photography for which it may be desirable to use developers that produce low-contrast or high-contrast images. Specialized graphic-arts work is an obvious application for high contrast. Frequently, high-contrast films are used and the developer is required to produce only one tone and maximum black. The soft-working developers already mentioned generally use metal as the developing agent and a mild alkali. For more energetic working, hydroquinone is preferred with sodium carbonate or hydroxide as the strong alkali content. Very-high-contrast materials require developers based on hydroquinone and sodium hydroxide. These solutions do not keep very well and are generally made up in two parts. Designed for process materials, the ID13 developer is composed of equal parts of solutions A and B, mixed immediately before use and then discarded. The development times at 20° Care 2-3 minutes. The opposite requirement for low contrast, occasionally arises for inherently contra sty subjects in brilliant lighting. A popular formulation for that purpose is a simple metal-sulphite type (example: Agfa 14). Their development times at 20° Care 10-20 minutes, according to film speed and contrast required. The high-contrast and low-contrast developers are now used for specialized applications and by a few enthusiastic perfectionists.

Acutance Developers

A popular developer very many years ago was a simple metal-sulphite-carbonate solution which is commonly known as the Beutler formula. It is used at a dilution of 1: 10 as a one-shot developer, times of 7 -10 minutes were average, giving soft and finely-detailed negatives. This effect became known as acutance or the adjacency effect or more simply, high definition. It makes the image look sharper. The extra sharpness is an illusion. The Beutler developer and the many later formulations under the acutance or high definition label make use of the adjacency effect to present greater visual sharpness, although the actual resolution of fine detail might be lower than that produced by the orthodox developer. Acutance developers rarely contain a restrainer because it is considered that such an addition would inhibit the adjacency effect. Nevertheless, alternative formulae by Geoffrey Crawley use potassium iodide in minute quantities. It is used once only at 200 C, FX-1 gives development times of 12-15 minutes. Effective film speed is said to be increased by 1; 2-1 stop. There are many branded acutance or high definition developers and they have a valid use. They are not formulated for general purpose working. They are not fine grain developers. Ideally, they are for use with inherently fine grained films of a lower rated speed than ISO 100/210 and with first class lenses on both camera and enlarger. Exposure and processing must be exact.

Developer Types

Developers can be roughly divided into various categories such as fine-grain, low-contrast, acutance, high-contrast, etc. The term fine-grain is now in fact obsolescent. The advances in emulsion manufacture have been such that the use of special developer formulations to make the necessarily granular structure of the image less evident in the print is totally unnecessary. The slower films are truly fine-grained and 35 mm negatives can be enlarged a long way beyond the requirements of most users before any really obtrusive graininess becomes evident. The standard developer formulation for use with all types of black-and-white continuous tone films (as opposed to line, copying or graphic arts films) is the metal-hydroquinone (MQ) or Phenidone-hydroquinone (PQ) plus borax type, characterized by the now almost historic ID 11 from Il ford or D76 from Kodak. The used undiluted gives development times at 20° C of 6-9 minutes according to film speed. There are many closel related variations of the standard formula. A buffered version (example: increases the 2 g of borax to 8 g and adds 8 g of boric acid). The main advantage claimed for this version is that its activity is more constant throughout its life, whereas the basic version tends to increase in activity with standing. Most of these solutions necessitate prolonged development times and also incur the penalty of a reduction in effective film speed.

Developer constituents

The developers are chemical solutions, sometimes simple, sometimes rather more complex. The four most important chemical constituents in a developer for black-and-white films have accepted labels, apart from their chemical names. The Developing agent should be the preferred term because there are innumerable reducing agents (chemical solutions that can reduce silver halides to metallic silver). The requirement for a developing agent, however, is that it shall reduce light-struck grains much more rapidly than those that have received no light, preservative, accelerator and restrainer. All developers must also contain a solvent and that is almost universally water. So given proportions of four readily-obtainable chemicals dissolved in water can form a developer. In practice, the solution is more likely to contain five chemicals because as we shall see, metal and Phenidone work best in conjunction with hydroquinone. The Metal and Phenidone work in similar ways. They produce an initial density rapidly but do not build to a high density. It is used as the only developing agent they produce soft but fully detailed images. The hydroquinone is used as the only developing agent has the opposite tendencies. It is slow starting but eventually builds to a high density in highlight areas. The image is generally too contra sty for normal use. Used together in suitable proportions, however, metal and hydroquinone, or Phenidone and hydro quinine bring the best out of each other to form fully detailed negatives of adequate density in a reasonable time.