Pyrocat HD

Pyrocat Versions and Mixing Directions
by Sandy King, March 2010
Below are mixing directions for various versions of Pyrocat, including DHD, -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.

HD: High Definition
C: Vitamin C (Ascorbic Acid)
M: Metol
MC: Metol + Vitamin C
P: p-Aminophenol
PC: p-Aminophenol + Vitamin C

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 potassium 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 carbonate solution would become One Part A + Five Parts B + 100 Parts water.

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

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.

Part A
Distilled Water (50¡ C) 750 ml
Sodium Metabisulfite 10 g
Pyrocatechin 50 g
Phenidone 2.0 g
Potassium Bromide 1.0 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 one liter of Pyrocat-HD Stock A solution in propylene glycol:

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.
Pre-heat 750ml of propylene glycol to about 150F in a water bath or hot plate stirrer.
Add the pyrocatechin to the warm glycol and stir until dissolved. Should take no more than about a minute.
Add the phenidone and stir. Should dissolve completely in about a minute.
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.
Top off the solution with glycol to 1000ml.

Mixing Directions for Stock B:

Start with 700ml of distilled water.
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.
Add distilled water to 1000ml.
Pyrocat-HD Stock Solution A, when mixed in propylene glycol, has a shelf life of several years.

B. Pyrocat-HDC (Solution A mixed in glycol)

Stock A
Propylene Glycol at 150F 750ml
Pyrocatechin 50 g
Phenidone 2.5g
Ascorbic Acid 4.0g
Propylene Glycol to 1000ml

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

C. Pyrocat-P (Solution A mixed in water)

Stock A
Distilled Water at 120F 750ml
Sodium Metabisulfite 10.0g
p-Aminophenol 5.0g
Pyrocatechin 50g
Water to 1000ml

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)
Propylene Glycol to 1000ml

E. Pyrocat-M (Solution A mixed in water)

Stock A
Distilled Water at 120F 750 ml
Metol 2.5g
Sodium Metabisulfite 10g
Pyrocatechin 50g
Water to 1000ml

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

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 (Solution A mixed in glycol)

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. (A small amount of TEA is used in the Pyrocat-MC formula to get the metol to go into solution. Pyrocat-MC can be mixed without the TEA by starting with the glycol at about 150º F, and stirring each chemical into solution.)

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.
Add Propylene Glycol to 1000ml.

Alternative mixing directions:
Heat 100ml of glycerin to about 250F and stir in the Metol, Ascorbic Acid and Pyrocatechin (no water or TEA required). Add Propylene Glycol to 1000ml. Mixed this way the solution will be even longer lived.

G. Pyrocat as a Two-Bath Developer

All of the Pyrocat formulas listed here (with the exception Pyro Uno) can also be used as a two-bath developer with excellent sharpness.
For further information, please refer to this article: Two-Bath Development with Pyrocat: a Simplified Methodology of Exposure and Development.

H. Pyro Uno

TEA 75 ml
Ascorbic acid 1.4 g
Pyrogallol 3.4 g
Metol 0.4 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 mins.