Pyrocat – Versions and Mixing Directions
By by Sandy King. Updated 04/2022

I am attaching mixing directions for various versions of Pyrocat, including –HD, -M, -P, -MC and -PC. I am indebted to Pat Gainer for his advice and recommendations for mixing the glycol based versions of Pyrocat, including Pyrocat-HD, -MC, and -PC.

Pyrocat-HD is the original Pyrocat formula and is still the most popular judging by sales and questions I get about it. The other formulas, which include Pyrocat-M and Pyrocat-MC, and Pyrocat-P and Pyrocat-PC are recommended primarily for rotary processing, where they tend to give slightly greater acutance than Pyrocat-HD.

All of the Pyrocat formulas are acutance developers that give good pictorial rendition when used at dilutions of 1:1:100 to 2:2:100 with normal agitation. When used at higher dilutions with reduced agitation they become high acutance developers with very pronounced adjacency effects.

Some of the characteristics of all of the Pyrocat variants are:
1. Good acutance.
2. Tight grain pattern.
3. Lower levels of general stain, even with long development times, than most pyrogallol based developers.
4. Does not cause uneven staining or streaking when developed in Jobo.
5. Can be used with dilute solutions and minimal agitation for very pronounced adjacency effects and enhanced apparent sharpness.
6. Very inexpensive to use.
7. Stock solutions last a long time. A year or slightly more when mixed in water, and up to several years when Solution A is mixed in glycol.

All of the Pyrocat versions use the same Solution B, which is a 75% solution of sodium carbonate. It is possible to substitute a 20% solution of sodium carbonate but if you do so the working formula must be mixed at 5X the amount of Solution B. Thus, a dilution of One Part A + One Part B + 100 Parts water when using the 75% potassium dichromate solution would become One Part A + Five Parts B + 100 Parts water.

A. Pyrocat-HD (For one litre of Stock Solutions A and B)

Part A

• Distilled Water (50° C) 750 ml
• Sodium Metabisulfite 10 g
• Pyrocatechin 50 g
• Phenidone 2.0 g
• Potassium Bromide 2.0 g
• Distilled Water to make 1000 ml

Part B

• Distilled Water 750 ml
• Potassium Carbonate 750 g
• Distilled Water to make 1000ml

Mixing Directions for Stock 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.
Tests show that the Pyrocat-A stock solution is stable in partially full bottles for up to a year. If shelf life of longer than one year is desired I recommend mixing Stock A in glycol. Stock Solution B has indefinite shelf life.

Mixing one-liter of Pyrocat-HD Stock A solution in propylene glycol.

1. Weigh out all of the chemicals for Stock A.
50.0g of pyrocatechin, 10.0g of sodium metabisulfite, 2.0g of Phenidone and 1.0g of potassium bromide.

2. Pre-heat 750ml of propylene glycol to about 150F in a water bath or hot plate stirrer.

3. Add the pyrocatechin to the warm glycol and stir until dissolved. Should take no more than about a minute.

4. Add the phenidone and stir. Should dissolve completely in about a minute.

5. Add the bromide and sodium metabisulfite to about 50-75ml of hot distilled water at about 120F. Stir until completely dissolved, and then add this solution to the propylene glycol solution.

6. Top off the solution with glycol to 1000ml.

Pyrocat-HD Stock Solution A, when mixed in propylene glycol, has a shelf life of several years.

B. Alternative Pyrocat-HDC mixed in glycol.
Pyrocat-HDC

Stock A
Propylene Glycol at 150F 750ml
Pyrocatechin 50 g
Phenidone 2.5g
Ascorbic Acid 4.0g

Pyrocat-HDC gives almost identical results as –HD with most films and development methods.

C. Pyrocat-P (Solution A mixed in water)
Stock A
Distilled Water at 120ºF 750ml
Sodium Metabisulfite 10.0g
p-Aminophenol 5.0g
Pyrocatechin 50g

D. Pyrocat-PC (Solution A mixed in glycol)
Stock A
Propylene Glycol at 150F
Pyrocatechin 50g
p-aminophenol 5.0g
Ascorbic acid 4.0g

(Mix in the order noted and stir until dissolved)

Water to 1000ml

E. Pyrocat-M
Stock A
Distilled Water at 120º F 750 ml
Metol 2.5g
Sodium Metabisulfite 10g
Pyrocatechin 50g

Water to 1000ml

Notes:

1. Mix the chemicals in the order given and stir until dissolved before adding the next chemical.

2. The use of the potassium bromide restrainer used in Pyrocat-HD is not needed with Pyrocat-P and Pyrocat-M because of the lower pH threshold of metol and p-aminophenol than phenidone.

F. Pyrocat-MC

Stock A
Propylene Glycol at 150F 750ml
Pyrocatechin 50 g
Metol 2.5g
Ascorbic Acid 4.0g

Mixing directions. Start with about 8ml of TEA at room temperature and a spoonful of water. Now add 2.5 g of metol and stir to make slurry. This is eventually going to make a liter but you can start in a 1/4-liter cup. After the slurry gets a little more fluid, add 15-20 ml of some warm propylene glycol. Now you can transfer the metol slurry to the 750ml of warm propylene glycol and stir until dissolved. Now add 50 grams of pyrocatechin and stir until dissolved. Add 4.0g of ascorbic acid and stir until dissolved.

Alternative mixing directions. Heat the glycol to about 250 F and all of the chemicals will readily go into solution with no water required. Mixed this way the solution will be even longer lived.

Pyrocat as two-bath developer. Many two-part developers can be used as two-bath developers. Barry Thornton’s Diaxactol was originally marketed as a two bath developer, though apparently not a very good one as it was later re-marketed as a single bath developer.

Pyrocat-HD can also be used as a two-bath developer with excellent sharpness. For this I recommend a 1:10 dilution of both Parts A and B, with solution temperatures at 75F.

1. Water bath for five minutes.

2. Six minutes in Part A, with two inversions at the beginning, and two inversions at the 1/4, 1/2 and 3/4 points of development.

3. Pour our Solution A and pour in Solution B. No rinse between. Initial agitation two or thee inversions, then two or three inversions at the 1/4, 12 and 3/4 points of development.

4. Pour out B, pour in water and leave for five minutes.

The purpose of the relatively long time in B and the final water bath is to allow developer exhaustion for maximum adjacency effects.

When used this way Pyrocat-HD is a high acutance compensating developer.

Pyrocat-HD negatives with the two-bath method described above have higher acutance than with one bath development and intermittent agitation.

Both Solution A and Solution B can be re-used several times within a three-four hour period but should be discarded at the end of a development session as they will go bad in about 10-12 hours.

Pyro Uno
TEA 75 ml
Pyrogallol 9.5 g
Ascorbic Acid 3.8 g
Metol 3.0 g

TEA to make 100 ml

Mix chemicals in order listed. Will dissolve easily with a hot plate stirrer at about 150F.

Working Solution: 1:50 to 1:200, 1:100 normal.
Starting point development time: 8-12 minutes.
Gives very low B+F, low general stain, and high image stain.