Pyro Processing

Pyro PMK-1 Notes

Pradip Malde: Large Format / Pt-pd printing, Jan. 2012, Sewanee.


Pyro = Pyrogallol (aka Pyrogallic Acid) derived from heated gallic acid

Used extensively in the 19th century, later by Edward Weston (ABC formula) among others.

The Stain

“The yellowish-green stain surrounds each reduced silver grain, fills in between them and becomes an inherent part of the image. The enlarging paper reacts to this stain as density. The total printing density of a stained pyro negative is the combined silver density plus the stain density. Film speed and printing quality are also improved. A stained pyro negative is acutely sharp and the visible grain effect is reduced. It thus contradicts what we can achieve with conventional developers.” From Gordon Hutchings, Pyro PMK Book


Edge effect: heightened chemically in Pyro yielding greater acutance

Highlight separation: By chemically binding and hardening the gelatin during development, Pyro restricts grain migration and halation to preserve delicate highlight values. The stained highlight densities print beautifully with little or no manipulation.

Fine grain: The “fusing” effect of the stain yields an extremely fine grain look.


Pyro-Metol-Kodalk: Pyrogallol the active ingredient is very toxic. Handle with great care, particularly in powder form, avoiding touching or inhaling dust. The powder should be white to off-white. Discoloration = deterioration. Metol  and sodium bisulfite are added to form SOLUTION A. SOLUTION B consists of sodium metaborate (“Kodalk”).

Working Solutions

1 part A, 2 parts B + 100 parts water = solution

e.g. 10cc of A + 20cc of B +1000cc of water

Measure the water and add A and B solutions to it. Note the color change to pale amber. This is an important visual check. I there is no color change something is wrong.


Development Times Ilford FP4+ (ISO 80) Ilford HP 5
Delta 400 (ISO 320)
Placement time (70F)
Normal+2 16 19
Normal+1 13 15
Normal 10 11
Normal-1 8 9
Normal-2  7  7

Temperature Compensation: 4% decrease in development time for each degree (F) over 70F.
Processing Steps

All solutions, including water, must be at the same temperature +/- 1F.

1. Presoak 1m plain water.
2. Developer Closed Tank: Open Tank: Tray:
  For tank development, use rubber gloves. 

For tray development, use disposable, non-sterile, medical gloves.

See above chart for times

2 vigorous inversions every 15secs throughout the development time. Note that this contradicts agitation methods when using ‘standard’ developers. Lift and twirl, recommended for 120 film. Lift and twirl every 15 seconds, with more twist than lift, up and down twice, first time twisting one way and the second time twisting the other way. Each complete operation should take 3 to 5 seconds. Use a tray one size larger than the film (e.g. 11×14 tray for 8×10). Use 1 to 1.5 qt for an 8×10 tray, 3qt 11×14 tray. At first, max. 2 sheets of film per tray, emulsion side up. Vigorous, rapid, random agitation, rocking the tray from corners in a random sequence. It is important to establish a random agitation pattern to avoid flow patterns.
3. Stop Bath 1m. Plain water. The presoak bath can also be used for this. Constant, random agitation.
4. Fix F-24 yields the best stain. Must be a non-hardening fixer. Fix for 6 minutes. Otherwise use any non-hardening fixing bath such as Ilford Universal Rapid Fix. Intermittent agitation okay, but constant recommended.
5. Stain-Bath 2m. Re-immerse in Developer solution. Alternative After-Bath solution: 0.5 teaspoon of sodium metaborate to 1qt water. Discard developer. Constant, random agitation.
6. Wash 20m
7. Photoflo 1m Gentle agitation
8. Dry at room temperature
9. After processing.. ..thoroughly rinse and dry all equipment.




Observation Cause Solution
Splotchy, uneven development Insufficient agitation Increase agitation
Edge marking, increased density. Flow patterns Too much repetitive motion Vary agitation more randomly
Markings across film. Flow patterns
Sharply edged patterns of lower density. Wetting problems, often caused in the first instances of the process. Increase the pre-soak time.

“Pyro is a simple, water soluble chemical, and present indications are that it does not accumulate in the body tissues. If contact is made, flush with water. If extensive contact is made or if in eyes, wash area thoroughly and consult a physician. If inhaled or swallowed, drink two glasses of water and induce vomiting by sticking finger down throat. Give milk or egg whites beaten with water. Get medical attention at once.”

All quotes are from Gordon Hutchings, Book of Pyro.



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