PMK Pyro

Film DeveloperConcentrate

Gordon HutchingsDilution: 1:2:100 (A:B:water)

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A modern pyrogallol staining developer designed by Gordon Hutchings.^[1] PMK produces a proportional yellow-green stain on negatives that acts as a printing density mask, effectively extending the tonal range of the negative. The stain is proportional to silver density, meaning highlights gain more effective printing density than shadows. Excellent for alternative processes (Pt/Pd, carbon) and for graded paper printing. Requires careful handling due to pyrogallol toxicity.^[2]

References

BOOK Gordon Hutchings. The Book of Pyro Bitter Dose Books, 1998. ↩
BOOK Anchell, Steve. The Darkroom Cookbook 4th ed. Focal Press, 2016. ISBN 9781138959170. ↩

Mixing Instructions

PMK is mixed as two stock solutions.

Solution A (Metol + pyrogallol):

Dissolve Metol in 700 ml distilled water at 20 °C.
Add pyrogallol and stir until dissolved.
Top up to 1 liter.

Solution B (alkali): Dissolve sodium metaborate in 1 liter of water at 20 °C.

Working solution: Mix 10 ml A + 20 ml B + 1 liter water (1:2:100 ratio). Use immediately — working solution oxidizes rapidly.

Wear gloves: pyrogallol is toxic and stains skin. Solutions A and B keep 6+ months separately in dark bottles.

Ingredients for 1L of Concentrate

Volume:

#	Chemical	Role	Qty (1L)	Unit	Note
1	Metol	Developing Agent	10.0	g	(Solution A)
2	Sodium Bisulfite	Preservative	20.0	g	(Solution A)
3	Pyrogallol	Developing Agent	100.0	g	(Solution A)
4	Sodium Metaborate	Accelerator	300.0	g	(Solution B)

Process Parameters

Temp:°C

Film Stock	ISO	Dilution	Temp	Time	Agitation	Source	Notes
Ilford FP4+ 125	100	stock (A+B+water)	20.0°C	10:00	Continuous first 60s, then 10s every 60s	Community data	Rate at EI 100.
Ilford HP5+ 400	320	stock (A+B+water)	20.0°C	11:00	Continuous first 60s, then 10s every 60s	Community data	Rate at EI 320. Beautiful staining negatives.
Kodak T-Max 100	100	stock (A+B+water)	20.0°C	12:00	Continuous first 60s, then 10s every 60s	Community data	T-grain films stain less with pyro developers.
Kodak Tri-X 400	320	stock (A+B+water)	20.0°C	11:00	Continuous first 60s, then 10s every 60s	Gordon Hutchings, The Book of Pyro	Rate at EI 320 for best stain density. Post-dev staining bath recommended.