Pictorial Planet

Peter Hogan's

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Prescysol™ is a general purpose pyro staining developer with fine grain and wonderful rendering of highlights. It utilises three developing agents, phenidone to maintain good film speed, metol for beautiful highlights, and pyrocatechin for long tonality, acutance, and stain. These three developing agents have been carefully balanced to create a developer for both classic grain films, such as FP4 Plus or Pan F Plus, or tabular grain (T-Grain) films such as Ilford's Delta or Kodak's TMax.

Prescysol™ - Instructions for use.

Prescysol™ is a specially formulated developer unsurpassed in its ability to provide superb negatives with extremely fine grain, remarkably high sharpness, smoothly gradated tones and delicate and translucent highlights. Prescysol yields full film speed; you can expose at the makers recommended ISO.

Prescysol™ is a tanning and staining developer. As the developer is absorbed, the emulsion is tanned, or hardened, and this hardening is variable, being greater in areas of greater exposure. As the emulsion tans, it inhibits the absorption of further amounts of the developing agent, and so development in these highlight areas is restrained. The lower tanning action in the shadow areas allows development to continue and these areas continue to build, producing negatives with rich, deep shadows, beautifully gradated mid-tones, and delicate highlights. Negatives developed in Prescysol™, particularly using the partial stand method, will yield full speed, exhibit high acutance, and will need considerably less burning-in to areas such as skies.

As development proceeds, oxidation and natural by-products of the process stain the emulsion brown, the staining being proportional to the exposure level of the various parts of the negative. The result is a continuously-variable mask of printing density across the tonal range of the negative. Further, as the emulsion is stained mostly between the silver grains the effect is to soften the grain and so produce a smoother tonality in large areas such as sky and mist, where grain can normally be such a problem.

Prescysol™ is an extremely tolerant developer; films of different make and speed can be developed together at the same time.

For example, HP5 Plus 400 (120 roll film) and Delta 100 (35mm) despite being of totally different grain structure, can be developed together in the same tank for the same time. In fact, the modern tabular grain films (which require closer control of times and temperatures in normal developers and are more susceptible to burned highlights and blocked shadows) will benefit enormously from being developed in
Prescysol™, yielding the fine grain, tone and acutance of which these films are capable.


™ is supplied as two concentrates which are diluted and mixed for use; a 100ml bottle of part A and a 500ml bottle of part B. This quantity is sufficient for up to 33 rolls of 35mm film, or 40 rolls of 120 film (if the 120 film is loaded two to a spiral).

When fresh, part A will have a light brown colour, and will go very dark brown as it deteriorates. Do not use it if it has gone dark brown. It will keep, in the bottle supplied and if an anti-oxidation spray has been used, for at least six months. If you wish to keep it longer, it is best to decant it into a brown glass bottle and use an anti-oxidation spray. Always store part A away from light. Part B is a clear(ish) liquid, and will keep indefinitely in the bottle supplied.



All development is carried out at 24C in small tanks. We recommend that you pre-soak the film for five minutes in water at the same temperature. With 120 roll film this soak will also remove the anti-halation dyes from the film.

™ is mixed in the proportions of 1+5+100. So for each reel of 35mm film use 3ml A , 15ml B and 300ml water, and for each reel of 120 film, regardless of whether you have one or two films loaded on the reel, you use 5ml part A with 25ml part B and 500ml water.

  • I personally like to develop in a little more solution than that to guard against uneven development. For 35mm film tanks I use 400ml of chemistry so that's 4ml A + 20ml B + 400 ml water.
  • For 120 film I like to use a minimum of 600ml so I mix 6ml A + 30ml B + 600ml water.

Note: in all cases we strongly recommend the use of distilled water. Tap water has too many additives, ph varies, and consistent, streak free negatives can not be guaranteed with tap water.

Pour the measured amount of water (300ml for 35mm film or 500ml for 120 film, scaling up for larger tanks), at 24 degrees C, into a clean container, and add the requisite amount of part A. Measure out and add part B, stir. As part B is added, the developer may start to darken and this is quite normal.

Pour out the pre-soak, and pour the developer into the tank. Agitate continuously for the first 60 seconds, and then for 10 seconds every 30 seconds thereafter. Agitation should not be too vigorous; a gentle inversion followed by a slight 'swirl', turned upright and 'swirled' again is sufficient. Two such manoeuvres every 30 seconds is ideal. The 'swirl' is a slight rotary movement of the drum sufficient to induce a
small sideways movement in the liquid. (This is to break up laminar flow and so prevent bromide drag - the streaking that results in all development if progressively exhausted developer is allowed to follow one path repeatedly) Development times are remarkably consistent for all films; 8 minutes is a good starting point and will produce extremely easily-printable negatives.

10 seconds before the elapsed time start to pour out the developer. The after-soak in used developer needed by other staining developers is not required with Prescysol™, and as this is one-shot, you can discard it. The used developer will normally be a much darker colour at this point. DO NOT USE AN ACID STOP. Staining developers work best in an alkaline environment, and an acid stop bath will reduce the stain.

Four or five, 10 second rinses in fresh water is ok, or you can use our unique

We recommend using freshly-mixed fixer, and our own Alkali-FIX™ is specially formulated to enhance the staining characteristics of Prescysol™. Fix for 5 minutes, then check the film. If there is any slight cloudiness, place the film back in the fixer until it clears. Tanning developers need longer fixing times than conventional developers. A running water wash is always better, but beware of suspended particles in the water; always use a filter. There is absolutely no requirement for the use of hypo-clearing agents when using alkali fixes, and they should not be used. If you have used Alkali-FIX™ a four minute wash is ample, otherwise wash as recommended by the maker of the fixer used.
If you are using tabular grain films, e.g. T-Max, and an acid fixer, DO NOT extend the fixing time in an effort to dissolve the extra dye used in these films. Simply let the film sit in 3 x 5 minute water baths after fixing and before washing. Any residual dye not cleared by these baths will be cleared by a short extension to the washing time.
Use of a wetting agent is by choice, and hang to dry.


This is our recommended method of development. Negatives developed using the partial stand method will show smoother grain, higher acutance (apparent sharpness) and hold more highlight detail, meaning easier printing, than the 'normal' method. The dilutions, mixing and temperatures are the same as for the normal agitation method. Pour in the developer and agitate continuously for the first 60 seconds then for ten seconds every 3 minutes. Allow the tank to stand undisturbed between agitations. Starting time is 10.5 minutes.

There will be a longer stand time at the end; that is ok. The rest of the procedure is as for normal agitation.

As always, we recommend that for ultimate control and results that you perform standard tests to discern your personal film speed and development times. However, Prescysol™ is so forgiving and tolerant that using the makers ISO and following our instructions will yield superb negatives for the vast majority of applications, and far better than any normal developer.

NOTE: because solution B is a saturated solution, at low temperatures it may crystallise to form a sediment at the bottom of the bottle. Warming the solution in a water bath will return the crystals to solution. This will not affect the developing properties. Using a partially-crystallised solution will result in under-developed negatives.


Treat all chemicals with caution and keep out of the reach of children. Do not store chemicals in bottles designed for other use, e.g. lemonade bottles. Use gloves during use, and wash from the skin with plenty of fresh water. In case of contact with the eyes, wash with plenty of fresh water and seek medical advice. Wipe up spills immediately and wash or swab with clean water.


No liability is accepted by the producer or supplier of this product except for the value of the product itself if faulty. Expressly, no liability can be accepted for any consequential loss or injury howsoever caused. The producer/supplier will be pleased to refund the full purchase price provided the faulty product is returned within 30 days from date of purchase. Use of the product implies acceptance of these conditions.

© Peter Hogan. No part of this document may be reproduced in any form without written permission.