Paterson 'Acu' Monochrome Chemistry

The table below tries to show the approximate chronology of the Paterson 'Acu' range of developers.
Clicking on the names takes you to a place on the web page (below) which shows more detail about each product. The dates within the table header should not be taken to imply the date a product first appeared (though the date for the original Acutol is believed correct). In general the dates are merely dates for which information is available.

Information on other 'Acu' products, not developers, can be viewed here.

Nov 1963

June 1964

Aug 1965

Jan 1968

Oct 1969



Sept 1985

Jan 1994

Autumn 1998

2002 ~ 2007



Acutol FX-14

Acutol and in 2002

Acutol-S FX-15 Just Acutol-S in 1964

  Acuprint FX-17
Initially just named Acuprint, it reverted to this by Autumn 1998


Acuspeed FX-20


Acuspecial FX-21

Aculux FX-24

Aculux 2 and in 2002

Aculux 3
(new formulation)

Universal FX-26

Universal and in 2002

Pro-Print FX-34
Just Pro-Print in 1984;
Phototec Scales Brand in 1998

Acutec FX-35

Acugrade also see latest

FX-39 and in 2002 also see latest


P-Tec Unitol

The name of Paterson still exists in the world of photographic equipment supply and they can be contacted at:
Paterson Photographic Limited, 2 Malthouse Road, Tipton, West Midlands, UK. DY4 9AE. Telephone: 0121 520 4830 Fax: 0121 520 4831; Email:
They still offer a wide range of photographic darkroom products.

Geoffrey Crawley, world renowned photographic scientist, author, inventor and journalist, died aged 83 on Friday 29th October 2010.
The following notes were extracted (with minor editing) from 'Editor's Notebook', of Good Photography magazine, dated July 1962.
Mr. Crawley was occupied for many years in full time research into the technical and scientific aspects of photography; three of these years were spent in research into the development process, and the range of developers he formulated is incorporated in the Annual published by the British Journal of Photography; in July 1962 he was Technical Consultant to the 'BJ.'.
In addition to research, he constructed for himself many types of photographic apparatus, including cameras, exposure meter, enlargers and tripods - he also takes photographs!

Paterson introduced its own comprehensive range of black & white chemistry, starting with Acutol, a fine grain, high acutance, developer in autumn 1963 (Amateur Photographer reviewed it in their 30th October 1963 issue). It was invented by Geoffrey.W Crawley (see his picture, left)

Sold in screw-capped 220cc (7.5 fluid ounce) metal cans, requiring to be diluted 1:6.
The original Acutol instructions, dated November 1963, are shown below.

Acutol was made more concentrated, packaged in 170cc (6 fluid ounce) glass bottles and re-named Acutol FX 14 in early June 1964 (ref: AP 10th June, What's New?). Its standard dilution changed from 1:6 to 1:10 and the bottles incorporated a sealing washer to ensure efficient re-sealing after being opened. This was to counter adverse claims of the original's poor keeping properties. Price remained unchanged at 4s (25p) even though the greater concentration gave 25% more working solution.

INSTRUCTIONS FOR USE. Acutol is a concentrated liquid developer which has unique qualities in producing the maximum possible sharpness, definition and resolution obtainable on slow and medium speed films, together with a fineness of grain and full tonal scale which represents a new standard in "high definition" developers. Acutol is not a "Beutler" type developer, but like other developers designed for acu-tance Acutol has as part of its action the function of increasing "edge" sharpness by producing adjacency effects which heighten the contrast at the edge of fine detail. Normally this is done by using a dilute developer which necessitates a long development time, and sometimes restricts keeping qualities. In Acutol, chemical means are employed to produce and artificially enhance edge effects. This allows the developer to have markedly shorter development times and improved keeping qualities.
Apart from its adjacency effect mechanism, Acutol has a further action which ensures maximum definition on those types of film which do not readily respond to this mechanism. Consequently its special advantages are obtained no matter with what make of film it is used. This second action is achieved in part by a system of "buffering" which also results in the exceptional gradation and minimising of grain given by the developer.
Acutol is an unpublished formula invented by the leading independent authority on
the development process, G. W. Crawley, whose work on high definition development is well known. This formula is available only in the form of Paterson Ac
EXPOSURE. Acutol gives a slight increase in film speed, and it is recommended that films should be exposed at a meter setting ½-stop higher than the manufacturer's rated speed for minimum exposure.
1 part of the concentrated liquid is diluted with 6 parts of water. In order to find the amount of concentrated liquid needed to make up a given quantity of developer, divide the quantity required by 7.

English measure users may find it convenient to make up to one of the following volumes, which will suit the capacities needed for different film sizes in most makes of tank with very little wastage:-
1oz makes 7oz.
l.25oz makes 8.75oz.
1½oz makes 10½oz.
2oz makes 14oz.
Use once and discard.
The working solution should be used once only and then discarded. In an emergency it is possible to re-use the working solution if the development time is increased by 50% but the grain and gradation qualities may be affected.
KEEPING QUALITIES. Acutol will keep almost indefinitely in the unopened can. After opening and use of part of the contents the concentrated solution still has exceptional keeping qualities. Even when discoloured to a light golden tint the working properties of Acutol are not affected and the solution may still be used with confidence.
CONTRAST CONTROL. The times given below will give negatives of the type usually known as of "enlarging quality" with average contrast subjects. Owing to the variation in sensitometric properties of different films the "Gamma" value reached will be between about 0.5 and 0.65. The critical worker may desire to make slight adjustments in the development times to obtain the exact type of negative he prefers, but normally the times given below should be used, and will result in excellent negatives.
AGITATION. It is particularly recommended that agitation should be standardised in order to obtain consistent results. Two forms of agitation are in common use- inversion of the tank and rotation of the spiral in the tank. The times given below are based on one inversion per minute using a Paterson tank (any model), or 5 secs, rotation of the spiral per minute. Inversion agitation is recommended and the following technique may be used:-
(1) Pour in the developer and give the spiral several quick twists to dislodge air bells. Leave for one minute.
(2) After one minute invert the tank once and immediately return to the upright position.
(3) Repeat (2) at the end of each minute of the development time.
It will be noted that in the technique above the tank is not inverted during the first minute of the development time. This is to allow the film to become saturated with solution. If the tank is inverted immediately after the solution has been poured in and before the film has become saturated, air-bells may occur at the top edge of the film.
AFTER TREATMENT. Acutol does not form scum and the use of a stop bath is optional. It does not soften the emulsion and any fixer or fixer hardener can be used.
ADOX-35mm films
KB 14  5mins
KB 17  6mins
KB 21 9mins
ADOX Roll films
R14 5½mins
R 17 7mins
R21 11mins
AGFA-35mm films
IFF 6mins
IF 9mins
ISS 10mins
AGFA Roll films
IFF 7mins
IF 10mins
ISS 12mins
FERRANIA-35mm flms
P24 6½mins
P30 8mins
P33 10mins
FERRANIA Roll films
P24 7mins
P30 9mins
P33 11mins
GEVAERT-35mm. films
Gevapan 27 7mins
Gevapan 30 8mins
Gevapan 33 11mins
GEVAERT Roll films
Gevapan 27 8mins
Gevapan 30 9mins
Gevapan 33 12mins
ILFORD- 35mm. films
PanF 5mins
FP3 Ser 2  6½mins
ILFORD Roll films
FP3 Ser 2    9mins
Selopan 12mins
KODAK- 35mm. films Panatomic-X... 5mins
Plus-X Pan ... 8mins
KODAK Roll films
Panatomic-X... 7mins
Plus-X Pan Prof  8mins
Verichrome Pan 9mins
PERUTZ- 35mm films
Perpantic 17... 7mins
Peromnia 21... 10mins
PERUTZ Roll films
Perpantic 17...8mins
Peromnia21... 11mins

DEVELOPMENT TIMES FOR PLATES AND CUT FILMS. Acutol is perfectly suited to the processing of plates and cut films in the slow to medium speed range.
Plus-X Pan Sheet film.

9x12cm & 1/4plate-11min
5x4cm & ½plate-12min
P.300 Plate
9x6cm.- 7 min
9x12cm & 1/4plate-8min
5x4cm & ½plate-9min
FP3 Ser. 2 Sheet Film

9x6 cm-9 min.
9x12cm & 1/4plate-10min
5x4cm & ½plate-13 min
FP Special, R25 plate
9x12cm & 1/4plate-9min
5x4cm & ½plate-11min
FP4 Plate
9x12cm & 1/4plate-9min
5x4cm & ½plate-10min
DEVELOPMENT TIMES AT OTHER TEMPERATURES. Acutol gives identical quality at all temperatures. Care must be taken however to give precise times at high temperatures otherwise contrast may be too high. Changes in development time with temperature over standard time at 68°F (20°C) are given in the graph (see below).
To use, follow curve for development time at 68°F (as given in table for film) and read off time on base of graph at temperature required.


PATERSON ACUTOL-S (FX-15) SOLVENT TYPE DEVELOPER (FX-15 is the short tin in the Amateur Photographer advert, below)

* Fine grain
* Outstanding image sharpness
* Superb rendering of subtle tones
* Long life in deep tanks
* Re-usable without quality loss
Acutol-S is a re-usable solvent type developer which produces fine grain negatives exhibiting superlative gradation from shadow tones through the middle tones into the highlights. It is suitable for use with all makes and speeds of films and plates including the fastest modern emulsions. Unlike other solvent developers Acutol-S retains excellent image sharpness with very full film speed, allowing an increase of 2/3-stop over the makers rating. Acutol-S can also be used as a one-shot compensating developer with dilution techniques. Supplied in powder form in the following sizes:-
Tin to make 21 ozs (600ccs.) working solution. Price 4/6d. Tin to make 80 ozs (2.25 litres) working solution. Price 8/6d.
Tin to make 1 gall (4.5 litres) working solution. Price 14/-.

FX15 Acutol S, according to this website, has the ingedients:
Metol 3.5g
Sodium Sulphite (anhyd) 100g
Phenidone 0.1g
Hydroquinone 2.25g
Sodium Metabisulphite 0.5g
Borax 2.5g
Sodium Carbonate (anhyd) 1g
Potassium Bromide 1.5g
Water to 1 litre

(now 1:10 dilution, not 1:6 as original)

Acutol gives maximum definition on films ISO 5-200 by increasing the apparent sharpness at the edges of fine detail.
It achieves this effect chemically, so allowing normal agitation and giving negatives of excellent gradation. There is only the slightest compression of the middle tones, more than compensated for by the brilliance of detail within the picture. The edge effect is most marked on high acutance films, which are generally 35mm films of speed rating ISO 5-200. As these slower films usually have quite high contrast, Acutol suits them very well and will produce impressive results on subjects containing textures.
Films faster than ISO 200 and most roll films do not give the extreme sharpness of which this developer is capable. Acutol is a medium fine grain developer and while it will give good results with fast films and roll films it is normally preferable to use Aculux and so ensure the finest grain and longest tonal range.
Acutol gives a ½stop speed increase, useful with the slower films and is well suited to pictorial photography.
Dilution 1 + 10

A July 1991 instruction leaflet for Paterson Acutol FX-14, giving development times for dilutions of 1:10, 1:15 and 1:20 can be viewed here.

ACUSPEED FX-20 DEVELOPER (see development times above)
The effective speed of a film cannot be increased by simply extending the time of development in a conventional type of developer, since such a procedure merely means under-exposure and over-development and results in difficult to print negatives. Film speed increase can only be achieved by using a developer specially formulated for that purpose. Acuspeed is specifically intended for pushing to the limit the speed of fast films such as Kodak Tri-X, llford HP5 or other films of ISO400 and above. These particular films, normally exposed at ISO 400, can be exposed at IS0 1250 when processed in Acuspeed. This setting is based on the standard degree of shadow detail in normal subjects.
If detail in the deep shadows is not important, still higher speed ratings can be used. In these cases a little extra development will maintain sufficient contrast in the mid tones and highlights.
Sharpness is good and there is minimum effect on the evenness of tonal separation.
Acuspeed is a valuable standby, able to produce pictures where a standard developer would fail to give a useful negative.

A July 1991 instruction leaflet for Paterson Acuspeed FX-20 at dilution 1:7 can be viewed here.


ACULUX FX-24 DEVELOPER (see development times above)
Aculux is supplied as a liquid concentrate simply requiring dilution with water and it has been formulated for one-shot use. It is a fine grain developer, of the solvent type, suitable for films of all kinds, slow or high speed, and for all sizes of film, 35mm, roll or sheet.
On the slower films up to ISO 200 it gives a beautifully fine grain image with a superb tonal range from deep rich shadows right through evenly spaced mid-grey tones to brilliant highlights and image definition is well maintained.
On faster films Aculux keeps the grain to a minimum and makes the most of their tonal range. There is an added bonus of a 1/3rd stop increase in film speed.
Dilution 1 + 9

A July 1991 instruction leaflet for Paterson Aculux FX-24, can be viewed here.

Universal developer is suitable both for films and for papers. It is ideal for circumstances where the economy of one bottle of developer is helpful, such as for example, to a beginner.
Negatives developed in Universal will be crisp in detail, bright in contrast and with low fog level. They will print easily to show a wide range of tones. The dilution for films is 1 + 19, making it very economical.
For prints, Universal Developer is diluted 1 + 7, It gives rich blacks, pure base whiteness and a good range of middle tones with a neutral image colour. To make a rapid-acting Press-type developer, Universal can be diluted 1 +4. At this dilution it is also useful as a high contrast developer for copying or other special darkroom effects on film or paper where a normal film or print developer would be too soft-working.
Standard dilution for films: 1 + 19 and for papers: 1 + 7.
To view instructions as supplied with the bottle of concentrate FX-26, see below (courtesy of Luca Liverani).

PATERSON UNIVERSAL DEVELOPER: FX-26; Warning; this developer is an alkaline solution. Avoid contact with the eyes. Prolonged contact with the skin can cause irritation.
Universal DEVELOPER PATERSON FX-26 is suitable for processing films and papers. Its concentrated liquid formula allows great economy of use. It produces bright and clear negatives with minimal fog and with increased exposure latitude. With paper, it gives a rich range of tones, from pure white to deep black.
Exposure of Films
Film sensitivity is as indicated by the manufacturer.
Dilution for Film Development
Prepare the solution for use by diluting 1 part of concentrated developer in 19 parts water. To calculate the amount of concentrate to use, divide by 20 the amount of developer required by the film developing tank. For example: to achieve 300cc, use 15cc of liquid concentrate. Discard the diluted developer after use.
Dilution for Printing Paper Development
Dilute 1 part concentrate developer to 7 parts water. Discard the solution when it turns yellow.
Storage and Conservation Qualities
Universal DEVELOPER FX-26 should be kept under cool (but not refrigerated) conditions, which will enable many months of storage without oxidation. The developer concentrate should not be used once it has oxidised beyond a dark straw colour; its properties will then being seriously affected. If part of the concentrate requires to be stored for several months, the risk of deterioration can be reduced by transferring it to a smaller bottle that is filled completely and closed tightly.
Development Time for Films
Use the development times shown in the table included on the bottle label.
Development Time for Printing Papers
The normal processing time is 1½ to 2 minutes at a temperature of 20°C. With plastic coated RC type papers the image appears faster and the development time can be reduced by 20%.
Film Development Agitation
To obtain consistent results agitation must be standardised. Agitation may be by either of two methods: by tank inversion or by rotating the spiral within the tank.
Development times given in the graph are for inversion agitation every minute using a Paterson developing tank (any model) or by rotating the spiral for 5 sec every minute. The recommended method is by inversion agitation. The procedure is as follows:
1 Pour the developer into the tank and rotate the spiral quickly in order to eliminate any air bubbles. Then leave the tank for a minute.
2 Invert the tank every minute, immediately returning it to its upright position.
If agitation is continuous, development times can be reduced by 20%.
After Treatment
The use of liquid Paterson Acustop is recommended. It is provided with an exhaustion indicator and immediately stops development and prolongs the life of the fixer.
FX-26 and Acustop can be used with any fixer or fixer hardener. However, use of Paterson Acufix is especially recommended as it ensures rapid fixing, has a long life, gives maximum quality of negatives and prints that require a minimum washing time.
High Dilutions
To increase the control of development, it is possible to dilute FX-26 in the ratio 1+29 in conjunction with a 50% increased development time;.This procedure is particularly recommended for high processing temperatures.
Kodak VP 110 film is best developed using Paterson Acuspecial developer, but FX-26 can be used if diluted 1+29, developing for 5½ minutes at a temperature of 20°C.
Time Saving
Diluting FX-26 concentrate 1+4 allows rapid development of prints in approximately 45 to 60 seconds. At this dilution it is especially suitable for use with microfilm or graphic art surfaces, producing high contrast effects.
Temperature Variation
Development times vary, depending on the temperature being above or below 20°C. Use the following instructions in conjunction with the graph (see above) for determining Time / Temperature variations.
To use the graph, firstly determine from the 'Development Times' table (above), the development time in minutes at 20°C corresponding to your specific film. Find that development time along the horizontal minutes axis of the graph and follow that line vertically upwards to where it intersects with the horizontal 20°C line (68°F). Then follow the curve passing through the 20°C line to the actual temperature of your developer and determine the revised development time by reading vertically downwards to the minutes axis.
In the case of a recommended 20°C development time that is not a whole number of minutes e.g. 4½ minutes, follow a curve between the two adjacent ones for 4minutes and 5 minutes.

ACUTEC FX-35 DEVELOPER (see development times above)
Acutec has been specially designed for use with continuous tone, general purpose films of speeds of up to ISO 200 and with high contrast, copy films.
It is a highly concentrated liquid developer and is supplied in the form of TWO solutions. This ensures a long shelf life, even in part empty bottles. When developed in Acutec, high contrast copy films now widely being used for general photographic and pictorial purposes will not exceed a certain limit of maximum density, however over-exposed the negative or high the subject contrast.
With all films, Acutec provides somewhat finer grain and better retention of micro-detail, by adopting a different chemical approach. These benefits are at their maximum in the case of high contrast copy films, such as Kodak Technical Pan 2415, Agfaortho 25, etc., possessing extremely fine grain and high resolving power. These films, which now find an increasingly wide use, pose the problem of controlling contrast, and at the same time preserving good separation of tones across the range from deep shadows to highlights. Acutec provides the complete answer to this problem, ensuring at the same time the highest standard of micro-detail resolution.
Exposure accuracy is more than usually important in the case of copy films in view of their virtual lack of under-exposure latitude. Cameras with built-in exposure systems should be set to the manufacturer's recommended film speed setting as a starting point. If readings are taken from shadow areas, however, film speed settings may, with experience, be increased by one-third to two-thirds of a stop. With general purpose films a gain in film speed of a full two-thirds stop is attained.
The developer is supplied in two 100ml bottles, sufficient to process ten 135-36 films.

Acuprint is designed for all black-and-white enlarging papers on traditional fibre base or on resin coated (RC or PE) base materials and for multi-contrast papers. It gives a superlative range of tones from bright highlights through to rich shadow detail and a dense maximum black. By retaining pure whiteness of the paper base it ensures a clean, sparkling image and it avoids image staining, even when the print is lifted out of the solution frequently.
The image appearance time is short, typically between 10 and 20 seconds, and the normal development time at 20°C/68°F is 1.25-1.75minutes for resin coated papers and 1.5-2 minutes for fibre base papers.
The capacity of Acuprint is exceptional, allowing at least 80 average-density 20.3 x 25.4cm (8x10in) prints to be developed in 1 litre of working solution with no change in image quality.
Acuprint is metol free and therefore avoids the dangers which metol-based solutions have for some allergic users.
Dilution 1 + 9

A 1981 Paterson Acuprint FX-17 instruction leaflet can be viewed here, together with an instruction leaflet for the same chemistry in November 1998.

Acuspecial FX-21 had appeared by autumn 1969

A new type of soft working 'surface' developer invented by Geoffrey Crawley. "It is designed to give a special result with modern high performance slow and medium speed miniature films 5-200 ASA but may also be used with higher speed films. Acuspecial produces a negative of 'engraving' type sharpness and definition, coupled with extremely fine grain. The emphasis on this type of definition is obtained with a minimum reduction in continuous tonal gradation, and this is offset by exceptional separation of tones on fine detail. The disadvantages of streaking and inconsistency of action, usual to surface developers, have been overcome. There is an effective film speed increase of a half-stop.

Acuspecial does not replace Acutol which continues to give the optimum balance of tonal gradation, sharpness and definition. But the 'engraving' type negative given by the new developer, and the control of contrast which its soft working action provides, make it an important new tool for the knowledgeable photographer in the miniature and sub-miniature fields. Acuspecial is available as a highly concentrated liquid which is normally diluted 1:29 for use. Full instructions are supplied. Recommended prices: 55ml (2fl.oz) bottle 5/- 250ml (8.8fl.oz) bottle 17/6."

Paterson's brochure for 1973 / 1974 shows no new additions to the range, though some of the packaging has changed.

Back row; Acufix (medium), Acustop, Acutol, Acuprint, Acuspeed.
Acutol-S and FX-18 (small tins), cleaning solution, Acufix (small)
Acustop, Acutol-S (large tin)
Front row; Anti-Static Wetting Agent, Acuspecial

FX-18 Developer. A standard P.Q. Borax developer conferring advantages when used instead of the more conventional M.Q. Borax developers. A single powder for rapid preparation. Gives full emulsion speed, fine grain, good image sharpness and has a long working life.

Paterson's brochure 'Darkroom Equipment' for August 1984 shows six developers, two are new, while two previous ones (those supplied as powders; Acutol-S FX-15 and FX-18) are no longer available. All chemicals are now supplied as liquid concentrates in plastic bottles.

There is a new 'Pro' range, called Pro-Print and Pro-Fix, in 2.5litre and 5litre containers only.

Paterson Pro-Print Developer is a rapid working, positive developer suitable for all black and white enlarging papers, producing a neutral image.
It is characterized by having a high capacity, 1 litre of working strength solution being capable of developing between 3 and 4 square metres of paper, equivalent to 60-80 20.3x25.4cm (8x10in) prints, depending on the proportion of heavily to lightly exposed areas on the prints.
Development should be carried out ideally at a temperature of 20°C. At that temperature a correctly exposed print on resin coated paper will give image appearance within 10-15seconds and development will be complete in 45-60 seconds. In the case of fibre base papers, the image will appear in 20-25 seconds and development will be complete in 1½minutes. Longer development times will not affect print quality, though excessive immersion will give rise to veiled highlights.
The developer is supplied in the form of a concentrated solution, which is diluted in the ratio of 1 part of the developer to 9 parts of water.

By 1998, Pro-Print is one of Paterson's economy range Phototec Scales Brand, and the bottle (1litre and 3litres) bears the simple name 'Rapid Print Developer'.

The Scales Brand trademark suggests it may have originally been part of the Johnsons of Hendon formulas purchased by Photo Technology Ltd in 1976.

Various Paterson bottles, believed to date from the 1980s to mid-1991.

A 1981 Paterson Acuprint FX-17 instruction leaflet can be viewed here, together with an instruction leaflet for the same chemistry in November 1998.

A July 1991 instruction leaflet for Paterson Aculux FX-24, Acuspeed FX-20, Acutol FX-14 and Universal FX-26 can be viewed here.

It was the subject of a Mini Test by William Cheung:
Practical Photography magazine, January 1994 but first appeared in autumn 1993.

"If you use variable-contrast papers you get the best results by using a dedicated print developer. Paterson's latest formula, Acugrade, is suitable for all variable-contrast papers.
To use, dilute Acugrade 1+9 with water. I tried it with Kentmere Kenthene VC paper and Agfa Multicontrast Premium. To be honest, until I tried Acugrade my results with the Kentmere paper were disappointing, even in a variable-contrast developer. Acugrade, however, gave solid blacks, clean whites and plenty of sparkle to my prints. It performed equally well with Premium and the resulting prints are brilliant.
The image appears fairly slowly to start with, but the build-up is rapid and a fully-toned print is achieved in one minute. An extra 15 seconds or so helped to give more highlight detail. Dish life is comparable with rival developers and print capacity is also good.
Acugrade's an excellent developer and is a welcome addition to Paterson's strong existing line-up of photo chemicals. Try it."

The Acugrade packaging had changed by 1998. The pack alongside contains 2 x 300ml bottles.

Modern variable contrast papers are characterized by their high printing speed and short development times. Acugrade developer has been especially formulated to exploit both of these features whilst generating high maximum density and providing better separation of shadow detail at any grade setting than other developers. The good rich blacks, truly neutral well defined middle tones and clean sparkling whites which Acugrade generates on the best of the variable contrast papers makes this the ideal standard print developer for today's materials.

  • Produces good rich blacks, neutral mid-tones and clean sparkling whites.
  • At 20°C the image appears at 5 to 10 seconds, full development at 45 to 60 seconds.
  • Also suitable for fibre based papers (development times x2).

Dilutions 1:9 or 1:14

The following tables of developing times and developer / film combination suitability, are taken from Paterson's Autumn 1998 brochure.
All developer dilutions have been standardised to 1 part concentrate to 9 parts water.

Instructions for several Paterson developers also feature in this July 1991 leaflet

For use recommendations and development times, see tables above

Aculux 2 can be used for all black and white films, regardless of speed or grain group. It is a one shot, fine grain developer, now reformulated to give a more compact grain structure, even better tonal gradation and improved highlight and shadow detail. When used with modern hi-tech films such as Paterson Acupan 200 it will produce almost grain-free negative of exceptional quality.
With films in the medium speed group, Aculux 2 produces very fine grain and long tonal range negatives capable of a high degree of enlargement.
With modern fast films such as Acupan 800 which, by its nature, has a more coarse grain structure, Aculux 2 keeps grain to an absolute minimum but still provides a wide tonal range.

  • New formulation, gives a more compact grain structure with improved highlight and shadow detail
  • Almost grain-free negatives with slow, fine-grain films
  • Gives film speed increase of 1/3 of an f-stop.

Acutol is a medium fine grain, high acutance developer. Acutance is the term used to describe sharpness of the image - particularly the edges of fine detail. The 'edge effect' of Acutol is most marked on slow, fine, conventional grain films up to ISO 125. As these are usually of high contrast, the compensating effect available with Acutol is also beneficial.
Normal dilution is 1+10 which gives only slight compensation, 1 + 15 and 1+20 dilutions give the opportunity to select a degree of compensation to suit the film and subject. Very high contrast films such as Kodak Technical Pan can be used for full tonal range subjects by developing at 1+20.

  • Medium grain, high acutance developer
  • Gives a speed increase of 2/3rds of an f-stop or EV
  • Choice of dilutions for controling negative contrast.

FX-39 is a one-shot high definition developer designed to allow a new standard of sharpness and definition to be reached. It has been designed to exploit the properties of films using advanced silver halide grain technology such as those in the Paterson Acupan Kodak T-Max, Ilford Delta, Agfa APX and Fuji ranges.
As the development times of many traditional films are short compared to these emulsions, FX-39 can be diluted to 1 + 14 or even higher for convenience, accuracy and great economy without any loss of quality. Calculating the new time could not be easier -just multiply the 1 + 9 time by 1.5X. At 1 + 19 diluted (2X normal development time) FX-39 gives a valuable compensating effect with extra shadow detail and the ability to cope with high contrast subjects.

  • Formulated to give optimum results with tabular grain films.
  • Gives the film manufacturers full speed rating.
  • Doubling of the ISO setting possible with extended development.
  • Also well suited to conventional grain films up to 200 ISO.

For use recommendations and development times, see tables above

Varispeed makes the most of the faster, modern B+W films, including their ability to be "push processed".
Films having an ISO speed of 400, can be exposed at 800, 1600, or even 3200 and still record shadow detail, without the increase in contrast that can occur with other developers. The full tonal range is maintained throughout the densities and pushed films have an image quality almost as high as those exposed at their ISO rating.
Most effective on ISO 400 films, Varispeed is by no means restricted to them; although there is less latitude for the developer to utilise on ISO 100 films, at least one stop increase can be achieved.
Varispeed should not be confused with earlier 'push processing' developers which yielded poor results at the standard rating. It yields excellent results when no speed increase is needed.

  • Suitable for any b&w film type or speed
  • Films can be exposed at up to 8 times their ISO rating
  • Maintains full shadow detail
  • "Rescues" underexposed films

Universal developer is suitable for both films and papers can be very economical for the beginner or those on a budget.
Negatives developed in Universal will be crisp in detail, bright in contrast and with low fog level. They print easily to show a wide range of tones with a neutral image colour. At 1+4. dilution it is also useful as a high contrast developer for copying or other special darkroom effects on film or paper.

  • Suitable for films or papers.
  • Ideal as a high contrast developer for special effects.

P-Tec Unitol Fine-Grain developer
Unitol, the well-known developer, from the long discontinued Johnson's chemical range. This developer gives good results and a minimum of grain with most of today's black and white films.

  • Can be used to "push" films by up to two stops with a minimum loss of quality.


Read a review of FX-50 by Roger Hicks that appeared in 'shutterbug' magazine in September 2002. Click here or the image to download the review as a pdf file

Recommendations and developing times for Paterson developers available in 2002, being Aculux 2, Acutol, FX-39, Universal, and FX-50 can be viewed here,
or click on the small images to the left and below.
Dilution is 1 part concentrate to 9 parts water for all developers.

For Microsoft Word format technical documents fully describing the current Paterson chemistry, visit the Paterson website.

Separate documents are available for Aculux 3 and FX-39 film developers, and for Acugrade FX-31 paper developer
and Acufix Rapid Fixer.

ACUFIX is a rapid acting fixer for all films and papers, based on ammonium thiosulphate as the fixing agent.
The normal dilution is 1+3, although 1 + 7 can be used if the shortest time is not important. The specially buffered formula increases the capacity of the working solution, such that a minimum of 70 average 20.3x25.4cm (8x10in) prints can be treated in 1 litre. The formula also makes Acufix exceptionally resistant to carry-over of developer, although a stop bath after development is to be recommended with any fixer.
The time required for most films is between ½ and 1½minutes at 20°C/68°F. It is equally effective with papers, which fix in V2 to 1 minute.
Acufix does not use a hardening agent and this keeps wash times to a minimum. Instead, an anti-swell agent in Acufix helps to prevent film or print emulsions softening excessively. Dilution 1 + 3 or 1 + 7

An instruction leaflet for Acufix, packaged by the Paterson Photax Group during the early 1990s, can be viewed here. The latest leaflet is available by acessing the Paterson website link, above.

Information on other 'Acu' products, but not developers, can be read below. Most of these are discontinued.


An acid stop bath between developer and fixer ensures accurate control of image quality by ending development at a precise time. This is important when modern developers with short development times are in use. The stop bath also extends the life and properties of the fixer by preventing the carry-over of harmful alkalis into the fixer. Such a stop bath is therefore justified not only in terms of more consistent image quality but also in terms of costs saved on fixer. By preserving the fixer there is less danger of inadequate fixing and subsequent lack of permanency of the image.
Acustop contains an indicator and the solution changes colour when it is exhausted. The stop bath is yellow when fresh and maybe used repeatedly until it starts to turn to purple, when it should be discarded. The difference in colour is visible under safelight conditions.
Dilution 1 + 30

Paterson Acutone Sepia is a sepia toner possessing the unique property of allowing darkroom workers the freedom to choose the exact shade of tone which best suits the picture.
This is achieved by means of an Additive, which, when added in various proportions to the toner solution, can produce a whole range of sepia tones from warm, almost yellow to cold, sepia brown.
The chemicals are supplied in the form of a kit containing Bleach and Toner concentrates and the Additive.
The BLEACH is a conventional rehalogenising bleach, but the TONER has been specially formulated to avoid the unpleasant odour, associated with sepia toning.
Bleach concentrate is diluted to make 1 litre of working strength solution. The washed print is immersed in this solution and bleaching is usually complete within 3 minutes. The bleached print is washed well and Toner concentrate diluted to make 1 litre of working strength solution. The Additive may now be added to the Toner solution in various amounts according to the shade of tone required, up to 100ml Additive per litre of Toner solution. The bleached and washed print is then immersed in the Toner solution for about 3 minutes, washed and dried.
Both the Bleach and Toner solutions may be retained for further use and used repeatedly until their action becomes too slow or incomplete.



This page last modified: 15th October 2016