Pyrocat HD and Mod.

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Pyrocat-HD and Mod


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The original Pyrocat-HD formula by Sandy King is as follows:

Stock A
Distilled Water 75ml
Pyrocatechin 5g
Phenidone* 0.2g
Sodium metabisulfite 1g
Potassium bromide 0.1g
Water to make 100ml

Stock Solution B
Distilled Water               70ml
Potassium Carbonate    75g
Water to make              100ml

* 0.25 grams of Metol may be substituted for the Phenidone with a slight loss in film speed but possibly better keeping qualities. Sandy King originally said 2.5g Metol could be used to replace the Phenidone but later found that 1/10th the metol gave the same developing action. Therefore adding 0.25g metol to the above formula should work in the same way. I have never used this new formula. (See Pytrocat-M below.)

For extra longevity, stock A can be made by dissolving the Pyrocatechin and Phenidone in 75ml of warmed glycol (65c - warm in water bath). Dissolve the metabisulfite and bromide in 7ml of warm water and add to the glycol mix. Top up with fresh glycol to 100ml. Will keep for years.

To make a standard working solution:

• Mix 1 part A with 100 parts water and then  add 1 part B just before development (1:1:100)
• For greater contrast, double the amount of B (1:2:100)
• Use 30 seconds initial agitation and 5 seconds each half minute thereafter
• For shorter development times use 2:2:100

Solution A keeps for 6 months in a tightly secured container (glass or PETE). Solution B keeps indefinitely.

Approximate developing times and dilutions at 20C: 

EFKE 25                  8 mins         1:1:100
FP4+                       12 mins       1:1:100 - great combo
Tri-X                        14 mins       1:1:100
Acros @ISO50       12 mins        1:1:100
TMax100                 7 mins         2:2:100
TMax400                 7 mins         2:2:100

Stand development

Stand Developing works well with Pyrocat-HD. It increases the sharpness through acutance (micro contrast) and helps tame overall contrast. To use Pyrocat as a stand developer try:

• Dilute to 2:2:500
•  Pre-rinse for 5 minutes in distilled water at 20c
• Agitate for the first 30 seconds and then 10 seconds every 10 minutes
• Total time 45 minutes (try 35 minutes for PanF+)
• Stand in a water bath of 20C to maintain temperature although temperature is not nearly as critical with Stand Development. A couple of degrees either side won’t make a noticeable difference.

Pyrocat-HD Mod for enhanced stand development

Ascorbic acid (a form of Vitamin C) has an additive effect with this developer, specifically, the Phenidone variant. By adding the tiniest amount of Ascorbic acid we improve the sharpness of Pyrocat-HD even more, without sacrificing the wonderful tonal qualities. Note that Sandy King and Patrick Gainer also experimented with this. Their formula is somewhat different.

To make a stock solution of Ascorbic Acid:

Mix 1 gram with 100 ml water to make a 1% solution.

Mix 10 ml of the above to 100 ml water to make a 0.1% solution.

1 ml of this will impart 0.001 grams Ascorbic Acid

Using the working strength 2:2:500 dilution as for stand development, add 2 ml of our 0.1% solution (i.e. you are adding 0.002 grams Ascorbic Acid which happens to be the same amount of Ascorbic acid as Phenidone in the working solution)

To develop with this enhanced formula:

•  Use semi-stand development
•  Pre-rinse for 5 minutes in distilled water at 20c
•  Pour in the developer and agitate for 30 seconds
•  Tap the developing tank to dislodge any bubbles
•  Stand for 45 minutes agitating for 10 seconds every 10 minutes

Pyrocat-P and -M

Sandy King, the designer/creator of Pyrocat HD, has been continuously looking to improve Pyrocat. He has now released the following new formulas for updated versions. The results are similar to the HD variant but are designed to give sharper results with rotary processing. I use the original above but for completeness have listed these alternatives.

Pyrocat-P (p-Aminophenol variant)

Stock Solution A
Distilled Water at 120ºF 75ml
Sodium Metabisulfite 1g
p-Aminophenol 0.5g
Pyrocatechin 5g
Potassium Iodide* 0.1g
Water to 100ml (Can also be diluted in Glycol for better keeping properties)

Pyrocat-M (Metol variant)

Stock Solution A
Distilled Water at 120º F 75 ml
Metol 0.25g
Sodium Metabisulfite 1g
Pyrocatechin 5g
Potassium Iodide* 0.1g
Water to 100ml (Cannot be diluted in Glycol)

Stock Solution B for both above formulas is standard

Distilled Water               70ml
Potassium Carbonate    75g
Water to make              100ml

* Note the use of Pot. Iodide restrainer used to be advised by Sandy King to enhance sharpness and/or reduce fog but he has subsequently said "there is no advantage at all in the restrainer and my current version of these formulas eliminates it".

Sandy has continued to work on this excellent developer to make it more reliable over extended periods. Kudos to Sandy who has given so much to the photographic community both through his developers and his online help providing answers to questions any support and motivation to so many that use his developer.