A Jolly Good Tanning!

There’s a second approach to automatically holding back negative highlight densities while shadow densities are nursed up in development to produce fine negatives capable of fine prints. It’s tanning. 19th century developers often used Pyrogallic acid as their main agent. This has the property of releasing by-products during development which tan the gelatine in which the film emulsion is held, but of doing this proportionately according to exposure density. Thus in the dense highlights tanning is greater and faster. This inhibits the access of fresh developer solution to the emulsion and the highlight is automatically restrained. It also encourages the formation of edge sharpness effects and inhibits softening of resolution. Pyro is known, along with Pyroctachin (which also tans) as the highest definition developer of all. It fell into disuse for various reasons. It gained a reputation for instability and inconsistency – it went off quickly and was hard to control. It is a hazardous material. It also stained film, hands and anything else with a yellow/green colour. The addition of sodium sulphite cut out the stain and helped to preserve but it was still expensive and less reliable than more recent agents such as Metol, But the stain is actually desirable to knowledgeable photographers. It stains the gelatine between the grain clumps. The stain colour is non-actinic. This means that it is printing density. So it at least partially "fills-in" the spaces between the grain clumps to smooth out the graininess significantly. Not only that, but the stain is again proportion- ate to the negative density. With variable contrast printing papers the yellow/green stain is the equivalent of a softer contrast filter, but one that is automatically varied according to the negative density. So highlights are automatically even further restrained and hold subtle detail in the print. With graded paper, the stain provides the opposite – extra printing contrast in the highlights. This means that pyro acts like a sort of Multigrade negative developer. If your neg, turns out soft, you can print it on a graded paper to gain extra contrast; if hard, on a variable contrast paper to lose 1 to 2 grades of contrast (depending on film and paper type).

The old bugbears of expense and lack of controllability/longevity have all been overcome with a pyro formulation known as PMK (Pyro/Metol/Kodalk) which is de- signed to give the greatest stain possible and the utmost definition. It is by Gordon Hutchings of the U.S.A. who has done a fine job of evolving and broadcasting its formula. Handle the Pyro with proper care when mixing following the supplier’s safety advice. Use distilled (not just purified or deionised water). Mix at low temperatures of about 26 degrees. Solution B is saturated and may well take 24 hours to dissolve with an occasional shake up at room temperature even with distilled water. You may even have to heat it a little. The solutions are used diluted one shot, are very economical, and the stock solutions last well over 12 months in well sealed brown glass bottles

Gordon Hutchings’ PMK formula

For use mix one part of Solution A with two parts of Solution B to 100 parts of water. Most roll film s take about 8 minutes at 2 I °C for graded paper, plus about 20% for V.C. paper.

Solution B is a saturated solution and should be mixed at room temperature. It will take several hours to fully dissolve. If you have trouble dissolving it completely, use twicwe the amount of water, and mix four parts of solution B with one part of A with 100 parts of water for use. Remember to save the used developing solution which should be dark brown in colour after use due to the oxidisation that causes the film staining. To achieve the right amount of staining, after the film is fixed, rinse it briefly in plain water, then resoak in the used developer with occasional agitation for 2 minutes. Discard the developer and wash the film in the usual way for at least 20 minutes when the stain will often further intensify. Stain varies according to the make and type of film. New on the scene is DiXactol^™, Barry Thornton’s own proprietary developer which is the only one to combine two bath development and improved tanning/staining ultra high definition development. For its tanning/staining and sharpness, HP5 Plus in 120 and sheet is brilliant. Delta 100 and T-Max 100 are great in 35mm. Also in all formats try Fortépan 100 from Silverprint – cheap and curly, but great tanning/staining and sharpness. For 127 try Jessops own brand film.

DiXactol^™ can be only be obtained by post from Barry Thornton.