Development time

Ilford FP4 Plus in Pyrocat-HD

8:00 at 21°C, 1+1+100 dilution, EI 100 (−⅓ stop).

Start timer · 8:00

Time

8:00

Continuous

Dilution

1+1+100

Temperature

21°C

Box speed

ISO 125

B&W

Development time

Dilution	EI	Time	Temp	Agitation	Timer
1+1+100	100−⅓ stop	8:00	21°C / 70°F	Continuous	Start timer

EI is the speed the film was rated at when shooting. Times marked “not yet verified” come from secondary sources and haven’t been checked against a manufacturer datasheet.

Other temperatures

18°C	19°C	20°C	21°C	22°C	23°C	24°C
11:07	9:57	8:53	8:00	7:07	6:24	5:47

Calculated from the 21°C time using Ilford’s temperature compensation factors, not taken from a datasheet. Most B&W developers behave well between 18°C and 24°C.

Mixing

Dilution	300 ml (one 35mm roll)	500 ml (one 120 roll)
1+1+100	See the developer’s instructions	See the developer’s instructions

How they work together

Pyrocat-HD: Fine grain, very-high acutance, full film speed, compensating contrast. Excellent highlight separation with olive-brown stain.
Ilford FP4 Plus: Often considered a benchmark for medium speed B&W. Notable sharpness and fine grain. Well-suited for high-quality enlargements.
Notes on this pairing: Sandy King's sheet-film rotary time, 70°F (21.1°C), 2 min presoak.

FP4 Plus in other developers

510-Pyro