So just how does Prescysol work, and what are its advantages?

During development with Prescysol, controlled oxidation of the developer occurs producing a brown stain. This stains the gelatin of the film emulsion, in the image area only, but in direct proportion to the latent image; the more exposure, the more stain. Further, it stains the gelatin between the silver grains, partially masking the grain and providing a uniquely smooth gradation. The brown stain of Prescysol works as printing density and acts as a continuously-variable contrast filter according to negative exposure, thus restraining highlights and holding subtle shadow detail in the print. Due to the density added by the stain, development time can be reduced to produce exquisitely translucent highlight values, unequalled in their ability to effectively render the delicate tones of, for example, light cloud, fog and mist.

As Prescysol’s staining action takes place within the surface of the emulsion, fog is virtually eliminated, and bromide migration and halation remarkably reduced, resulting in higher acutance, or edge sharpness.

As well as restraining highlight development, Prescysol’s high energy develops shadow detail that might otherwise be lost with other developers, thereby effectively increasing film speed, but not by the usual mechanisms – longer development time, more active developers – that often increase film contrast and grain as an undesirable side-effect. You can, therefore, happily expose your film at the maker’s suggested ISO speed.

Tanning is a term used in leather processing, and means to harden and stain the proteins in hides to produce leather. Since the gelatin used in photography is also a protein, the hardening and staining also occurs in the negative emulsion. This tanning works to harden the gelatin, but again, in direct proportion to the exposure received; the more the exposure, the more the hardening, continuously variable across the negative. As the gelatin hardens, it restricts the amount of developer able to be absorbed, and so acts as a self-limiting barrier, reducing and holding back development in those delicate highlights whilst shadow detail continues to build.

The brown stain of Prescysol has advantages over the yellow-green stain of pyro too. When printing on graded silver papers it will be found that the brown stain of Prescysol filters out more of the bluewavelength of the enlarger light, and to which silver papers are sensitive, than the yellow/green of pyro, effectively increasing contrast by as much as one paper-grade.

Variable contrast (VC) papers have two emulsion layers; a blue-sensitive high-contrast layer, and a green-sensitive low-contrast layer. The yellow/green stain of pyro negatives holds highlight detail extremely well, but the price of extending the luminance range is a loss of contrast in the highlights. In other words, the higher the luminance the more ‘shoulder’ you will see in the curve of the print which translates as a flattening, or lowering of contrast in the highlights. In fact, this shouldering often begins in the upper mid-tones so you will also see some flattening in these areas too. One of the major problems with pyro is the lack of separation, or contrast in the upper mid-tones and highlights.

Brown stain will block green light more effectively than yellow/green stain, resulting in much less shouldering with Prescysol, resulting in prints on VC papers with more contrast in the highlights.

All this technical information is important, of course, but what does it mean for the photographers who just wants to get on and develop their films?

To summarize, Prescysol has the following characteristics:

• Very high acutance and great apparent sharpness.
• Very tight grain pattern.
• Fast acting.
• Produces very low levels of general stain and virtually no fog.
• Very consistent – does not streak or suffer from uneven staining.
• Can be used with normal, minimal or stand development techniques.
• Can be used in drum development.
• Gives greater film speed.
• Produces delicate highlights and rich shadows.
• Is economical and easy to use.

Prescysol can be used as a single bath with normal agitation, as a single bath with minimal agitation, and as a two-bath option. The minimal agitation and two-bath options give higher acutance and film speed. Because Prescysol is resistant to aerial oxidation, it can also be used in drum development without the streaking and unevenness that plagues pyro developers.

Development times are remarkable consistent too; 8 minutes for normal agitation, and 10.5 minutes for partial stand development are good starting points, and will certainly yield negatives of superb printability. (We recommend the partial stand technique as standard.) Films of different make and/or different speeds can also be developed at the same time, in the same bath, particularly in the partial stand and two-bath options.

Prescysol is supplied as part A (100ml) and part B (500 ml) and is mixed in the proportions 1 ml part A and 5 ml part B to 100ml water. It is consistent and easy to use, and there is no need or requirement for the after-soak in used developer as with other staining developers. Staining developers work best in an alkaline environment. (Anyway, plunging your delicate negatives into an acid stop bath and fix is tantamount to cruelty; besides reducing the staining, you are under real threat of dissolving away those translucent highlights you worked so hard for.) I therefore recommend the use of our alkaline fix. Although formulated specifically for use with Presysol it is perfect for any film and paper, negating the need for a soak in hypo-clear and reducing the wash time. Full instructions are supplied with all chemistry.

A full range of specialist developers, fixers, bleaches, re-developers and toners for discerning photographers requiring ultimate control for the production of fine monochrome prints will shortly be available.