Unblinking Eye
                             Pyro Staining Developers - Page 2



In early spring of 1998 I became interested in finding a staining developer which could work well in a variety of applications: rotary processing in Jobo, print drums, or BTZS tubes; in trays with intermittent agitation; and in tanks with minimal or semi-stand agitation. My experiments with Pyrogallol formulas were quite unsuccessful because rotary processing often led to high fog levels and uneven staining, while reduced agitation led to streaking and mottling. Then I turned to Pyrocatechin for my experiments. As Anchell and Troop observe in The Film Developing Cookbook, Pyrocatechin stains and tans as well Pyrogallol and is “generally considered to be more stable and reliable.”8   In addition Pyrocatechin is much less sensitive to aerial oxidation than Pyrogallol. Unfortunately none of the previous formulas using Pyrocatechin have been as successful as some of the Pyrogallol based formulas. Many use Sodium hydroxide as the accelerator and are, as Troop mentions, “too alkaline for modern films, tending to create unnecessary fog.”9 Too much alkalinity also leads to more pronounced grain, which is especially undesirable with 35mm and roll film formats.

After more than a year of experimentation I came up with the Pyrocat-HD formula, first published in Issue # 4 of The World Journal of Post-Factory Photography. I later made some minor modifications to the developer and the formula has been available in its present form at
http://www.unblinkingeye.com since the spring of 1999. Pyrocat-HD is currently sold as a kit by Photographer’s Formulary in the US and by Lotus Camera in Europe. The formula is carefully balanced and gives, with proper agitation, negatives of high acutance, a tight grain pattern, and when used with minimal and semi-stand development, enhanced adjacency effects. Pyrocat-HD also gives a slight speed gain with many films (as compared with PMK and Rollo Pyro), especially with the 1:1:100 dilution.

Pyrocat-HD is a Pyrocatechin/Phenidone based developer formula that has some clear advantages over Pyrogallol based developers in rotary processing of sheet film in tubes and drums because it is less likely to cause undesirable stain or uneven development. Many photographers have also found that Pyrocat-HD works well with tray processing, and I know of quite a few who are using it with development by inspection methods, including brush development. Moreover, subsequent tests and experiments with Pyrocat-HD have shown that it is also an excellent developer for use with 35mm and medium format films because of its high acutance and tight grain pattern.



I am not a developer gadfly and my philosophy with films and developers has always been to stay with things that work well. There are several very good staining developers and I have used and tested most of them. I used PMK as my primary developer for almost a decade but when I switched to rotary processing I began to have problems with uneven development, streaking and excessive general stain. I have been using Pyrocat-HD now for about five years and have not seen any of these problems. This fact, and the consistently high quality of my Pyrocat-HD negatives, is convincing proof to me that Pyrocat-HD is the most consistent and trouble-free of all of staining developers. It is characterized by the following attributes.

1. Very high acutance and a capability for great apparent sharpness on the print. My tests show that acutance with Pyrocat-HD is superior to other high-acutance developers such as PMK and FX-2.
2. Very tight grain pattern, virtually identical to PMK and FX-2, suitable for 35mm and roll film processing as well as sheet films.
3. Fast acting. Pyrocat-HD, even at the 1:1:100 dilution, requires shorter development times than both PMK and WD2D to reach an equivalent CI.
4. Very clean acting and produces very low levels of general stain, even with long development times. This makes it a very attractive developer for alternative printing processes that require negatives of very high CI.
5. Very consistent and does not suffer from uneven staining or streaking. It can be used with rotary processing with absolutely no fear of uneven development, streaking, or staining.
6. Can be used with minimal agitation when processing roll film in tanks for very pronounced adjacency effects that can result in great apparent sharpness.
7. Pyrocat-HD at the 1:1:100 dilution gives slightly greater effective film speed than other Pyro staining developers when negatives are developed to the same CI.
8. Pyrocat-HD is a better developer for making dual-purpose negatives, i.e. as for printing with regular silver papers and with AZO or alternative processes with the same negatives.
9. When printing with silver gelatin variable contrast papers Pyrocat-HD renders upper middle tones and highlights with more contrast than pyrogallol-based developers.
10. Pyrocat-HD is very inexpensive to use. When mixed from scratch it is much more economical to use than Pyrogallol based developers such as Rollo Pyro, PMK and WD2D.


Pyrocat-HD is mixed as two stock solutions that are diluted to make a working solution for developing. The shelf life of the stock solutions is very good. Stock Solution A can be stored in partially full bottles for up to a year, while Stock Solution B keeps indefinitely.


Stock Solution A

Distilled Water

750 ml

Sodium Metabisulfite

10 g


50 g


2 g

Potassium Bromide

1 g

Distilled water to make

1000 ml

Stock Solution B

Distilled Water

700 ml

Potassium Carbonate

750 g

Distilled Water to make

1000 ml

To make a standard working solution mix 1 part A with 1 part B with 100 parts water.

* Or substitute 25 grams of metol (with a slight loss in film speed)


Stock Solution A

1. Start with 750ml of distilled water.
2. Add 10g of sodium metabisulfite and stir until dissolved.
3. Add 50g of Pyrocatechin and stir until dissolved.
4. Mix 2.0g of Phenidone with about 5ml of isoprophyl alcohol and stir into an even paste, then add to the stock solution and stir until dissolved.
5. Add 1.0g of potassium bromide and stir until dissolved.
6. Add distilled water to 1000ml.

Stock Solution B

1. Start with 700ml of distilled water.
2. Weigh out 750g of potassium carbonate* and add the chemical very slowly to the water, with constant and rapid stirring. If you add the solution too fast, or don’t stir enough, it will be impossible to dissolve all of it in the water. As you add the chemical an exothermic reaction takes place and the solution will warm up appreciably.
3. Add distilled water to 1000ml.

    * Potassium carbonate is deliquescent, which means that it will absorb water from the air. It must be stored in sealed containers to prevent this from happening because if you weigh out 100g of potassium carbonate that has absorbed a lot of water the actual chemical weight might be only 60-80g, which of course would produce a much weaker B solution than the formula requires.


For developing negatives intended for printing with silver gelatin papers the recommended working solution is a 1:1:100 dilution.

One Part Stock Solution A + One Part Sock Solution B + 100 parts water.

For printing with AZO and most alternative processes, including carbon, kallitype, Pt/Pd, Vandyke, POP, albumen, and salted paper, a 2:2:100 solution is recommended.

Two Parts Stock Solution A + Two Parts Stock Solution B + 100 Parts water.

In most localities it is safe to mix the working solutions with tap water. However, if you see any unusual development artifacts such as sledging, streak marks, or uneven staining, the use of distilled water is recommended.


1. Metol can be substituted for Phenidone in the Pyrocat-HD formula at the rate of about 10 parts Metol to one part Phenidone. The substitution does not affect stain intensity or acutance but it may result in a slight loss in effective film speed. Note that the development times in this article are based on the Phenidone version of Pyrocat-HD and if you choose to substitute Metol these times may require adjustment.
2. Sodium carbonate can be substituted for potassium carbonate in the Pyrocat-HD formula. The two carbonates give virtually identical results when used at equivalent chemical weight in the working solution. However, sodium carbonate is much less soluble than potassium carbonate so it must be mixed as a weaker stock solution. To prepare a Stock Solution B with sodium carbonate, add 200g of sodium carbonate to 1000ml of water. To make a working solution for silver printing that would be exactly equivalent to the regular 1:1:100 dilution when using potassium carbonate, mix One Part A + Five Parts B + 94 parts Water. For alternative printing the working solution should be mixed 2:10:92 to exactly match the 2:2:100 dilution with potassium carbonate. For all practical purposes you could just mix the working solutions with sodium carbonate at 1:5:100 or 2:10:100 and make minor adjustments to development times as required.
3. Some people are using Pyrocat-HD with a 10% Sodium hydroxide Stock B solution in place of the carbonate. This appears to work fine but the increased alkalinity may give slightly increased grain with some films so test carefully before making this substitution. To make a working solution using 10% sodium hydroxide as Stock B dilute 1 Part Stock A + 1.5 Parts Stock B + 100 Parts Water. This working solution will give similar results to the regular 2:2:100 dilution using potassium carbonate. However, because of the possibility of increased grain size I only recommend the substitution of sodium hydroxide for developing negatives meant for contact printing.


1. Pre-soak for five minutes. The pre-soak is optional with tray and tank development (except with minimal and stand development), but it is absolutely essential with rotary processing.
2. Development for the time required in tubes, drum, tray or tank according to the instructions that follow.
3. Stop bath. I recommend the use of a dilute acetic acid bath of about 1/4 to 1/2 normal strength. If the stop bath is too strong it will reduce image stain.
4. The use of an alkaline fixer is recommended. Kodak and Ilford Rapid-Fix work fine, as does Formulary TF-4.  I use the TF-3 formula described in Anchell and Troop’s
The Film Developing Cookbook.
5. One minute in a hypo-clearing agent. I use a 1% solution of sodium sulfite but any of the commercial products will serve the same purpose.
6. Wash in running water for 30 minutes.

Do not use an alkaline after-bath after fixing as recommended by Hutchings for PMK. My tests show that the stain added by this after-bath is primarily b+f, or general stain. General stain increases printing times and does nothing to enhance the printing qualities of your negatives.

Pyrocat-HD is capable of outstanding results with many different kinds of development methods. Some specific operating procedures for the various methods are provided at this point.


Because of its high resistance to aerial fog Pyrocat-HD is an excellent developer for tray development. Negatives developed in trays, even with long development times, will have very little general stain. This is due to the fact that Pyrocat-HD, unlike pyrogallol-based developers, is not very sensitive to aerial oxidation, considered to be the major cause of general staining. To avoid the possibility of scratching I recommend development of only one sheet of film per tray, but persons experienced with shuffle development procedures should feel free to develop this way . For even development use a tray at least one size larger than the film being developed: 8X10 trays for 5x7 negatives, 11x14 trays for 8x10 negatives, etc. This will reduce the possibility of uneven development at the edges caused by local hot areas that result from the increased speed of the developer as it bounces off the edge of the tray during agitation.

Always wear protective gloves with tray development to avoid skin contact. Although there is no history of long-term health problems from the use of Pyrocatechin as there is with Pyrogallol it should nevertheless be treated with the same level of care since it is also a toxic chemical.

Pyrocat-HD can also be used to develop film by inspection. As is the case with other Pyro developers the staining/tanning action also serves to desensitize film. There has been quite a bit of discussion regarding the use of Pyrocat-HD in this type of application on the AZO forum at Michael Smith and Paula Chamlee’s website. One of the conclusions that emerged from the discussions at this site was that when Pyrocat-HD is developed by inspection the use of an amber rather than green safelight makes it easier to see the degree of development. This is because the brown stain of Pyrocat-HD blocks green light and makes it difficult to evaluate the negative by transmitted light when using a green safelight. However, if you evaluate the negative density by reflected light either a green or amber filter work fine.

Another development method that has been used successfully with Pyrocat-HD is brush development by inspection. Use a dim green or amber safelight for inspection. Jorge Gasteazoro, a pt/pd printer from Mexico who uses this method of development, provides the following instructions.

1. Pre-soak the film for one minute.
2. Pour the developer on the film and immediately begin brushing with a wide Hake brush or some another type of fine bristle brush. Brush from top to bottom with light strokes, then from side to side. Then repeat the sequence. To keep the film from moving hold down one of the corners with your fingers.
3. After about 70% of anticipated development time has expired, turn on the safelight, lift the negative from the tray and evaluate the degree of development by transmitted light.
4. Continue the above procedure until the negative has reached the necessary density, then transfer it to a stop bath and proceed as with other methods of development.


I developed the Pyrocat-HD formula primarily to eliminate problems I had experienced with other staining developers using rotary processing. By rotary processing I mean development of film in Jobo, in BTZS type tubes, or in print drums used on motor bases. I used PMK for many years with tray processing and was very pleased with the results. However, when I switched to rotary processing I began to experience a number of development problems, including high general stain, streaking on the emulsion side of the film, and unusual pressure marks on the base side of the emulsion that resulted from contact with the surface of the tube or from the ribs. Sometimes the streaks and pressure marks would not be visible when looking at the negative through visual light, but they would show up later during printing with UV light. I switched to Rollo Pyro, and while this reduced the high general stain it did not solve the problem of streaking and pressure marks. The use of Pyrocat-HD has eliminated all these problems in my own work and I strongly believe it is by far the best Pyro developer for use with rotary methods of development.

One of the big advantages of Pyrocatechin is that it does not oxidize as rapidly in alkaline solutions as Pyrogallol. However, with very active agitation, as in Jobo at maximum speed, Pyrocat-HD does indeed oxidize. For this reason I recommend very slow rotation to minimize oxidation when developing film in Jobo processors.

My recommended procedures for rotary processing are straightforward and conventional.

1. Start by loading the film into the tubes or drum. With some drums and tubes it may be necessary to load the film wet to make sure there is a transfer of chemicals on the base of the film.
2. Pre-soak the film for five minutes. Distilled water is recommended.
3. Discard the pre-soak water and pour the developer into the drum or tubes and begin development. I recommend a minimum of 50ml of the 1:1:100 dilution per 4X5” sheet of film (20 square inches). This amounts to about 90ml for 5X7, 200ml for 8X10, 385ml for 11X14, 300ml for 7X17, 600ml for 12X20, and 1200ml for 20X24. Remember, these are minimum amounts. With the 2:2:100 dilution the amounts can be reduced by about 20%.
4. Adjust your procedure as follows depending on whether you are using Jobo, BTZS type tubes, or print drums on a motor base.
Jobo — Rotation speed should be at the slowest setting available. This is very important because fast rotation will result in a large increase in general or b+f stain. If it is not possible to slow down the rate of rotation there are other options that will also reduce the amount of general stain. The degree of oxidation that can take place in an alkaline Pyro developer is controlled by the amount of sodium sulfite preservative in the working solution. With most forms of development Pyrocat-HD needs very little sulfite to prevent excess general stain and it is provided by the small amount of sodium bisuilfite in the A solution, which serves two roles: 1) the sodium bisulfite acts as a preservative in the stock solution, and 2) when it mixes with the potassium carbonate alkali it forms sulfite through reaction.  However, when we develop film with rotary processing at high rotation rates the amount of sulfite is insufficient and general stain can result.. To counter this I recommend one of the following solutions: add 30% more of stock solution A when making up the working solution, or (but not also)  add about   0.3 g/L of sodium sulfite to each liter of working solution. Both solutions have the practical effect of bumping the amount of sodium sulfite preservative in the working solution and this will slow down the rate of oxidation.

BTZS type tubes — Develop by allowing the tubes to randomly bob about in a water bath, spinning each gently every few seconds. Do not agitate too vigorously.

Print drums on motor base — Remove the drum every minute or so and give it vigorous sideways agitation. This will break up any laminar flow patterns created by the one-plane rotation of the motor base and prevent bromide drag.

Pyrocat-HD can be used to develop 35mm, roll film, and sheet film in tanks following conventional procedures with no special precautions. Vigorous agitation is not needed with Pyrocat-HD as it is with pyrogallol-based developers, and with most films minimal agitation procedures can be used successfully. Stand agitation can also be used with some films. Slight modifications are necessary, however, depending on which of the three methods is used.

Normal Agitation — Normal agitation for tank development is considered to be continuous agitation for the first 60 seconds of development, then agitation for 5-10 seconds every 30-60 seconds thereafter.  With this pattern of agitation Pyrocat-HD can be used with no modification to your normal development procedures for conventional developers.

Minimal Agitation — Minimal agitation consists of continuous agitation for the first 60 seconds of development, followed by 10 seconds of agitation every third minute. With this method a pre -soak of five minutes is strongly recommended to avoid the possible formation of bubbles on the emulsion. Minimal agitation has three desirable results: 1) it gives great apparent sharpness through the formation of maximum adjacency effects,  2) it provides a compensating effect, and 3) it provides increased emulsion speed.

With minimal agitation you should extend development time about 50% over the normal time required for intermittent agitation, but experiment before risking valuable negatives.

Stand Development — Stand development is a highly specialized type of development that makes use of extremely dilute developers in conjunction with very long development times. It has as its purpose the creation of extreme adjacency effects and maximum apparent sharpness. It also gives maximum emulsion speed and provides great compensating effect. When it works, the results can be extraordinary, even stunning. Unfortunately this method of development is fraught with dangers and in practice it will be found that some films, especially high-speed films, are poor candidates for this type of development. And even when the procedure works well for a particular roll of film there will often be one or more frames that are ruined because of an air-bubble, bromide drag, or one of a number of other development artifacts that can plague this method of development. For this reason it is essential to test your film thoroughly, and to always make two or more back-up shots of important scenes when using stand development.

With stand development you should always pre-soak the film for about five minutes to eliminate the formation of air-bubbles. Should an air-bubble form on the film during stand development the negative will be ruined because the bubble will prevent any exchange of developer at that spot, and the effect will be to spread irregular circular patterns of up to 1/4” to 3/8 “in diameter around the bubble, ruining the frame or sheet of film.

The working Pyrocat-HD solution should be mixed at approximately 2:2:400-500, i.e. two parts A + two parts B + 400-500 parts of water for stand development. To begin development discard the pre-soak water, pour in the developer, and agitate continuously and vigorously for 60 seconds. Then, set the tank aside and leave it with no further agitation for the remainder of the development period.  Development times for most films will be in the 45-60 minutes range.

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