Black & white film development

This guide covers the step-by-step process of developing black & white film. The process consists of three main stages: developing, stopping, and fixing.

The steps at a glance

1. Mix the developer to the dilution on the bottle, at 20°C.
2. Pour it into the tank quickly and start the timer.
3. Tap the tank firmly on the worktop to knock off air bubbles.
4. Agitate as described below. When the time is up, pour out the developer. Most developers are used once.
5. Pour in the stop bath, agitate for 1 minute, and pour it back into its bottle.
6. Pour in the fixer, agitate for the fixing time, and pour it back into its bottle.
7. Now you can open the tank and wash the film.

Used chemistry needs care when you throw it away. See disposing of chemicals.

1. Develop

The first step is to develop the film, turning the latent image into a visible negative.

What happens in the developer

This is done by converting the exposed silver halide crystals into metallic silver. The metallic silver absorbs light and appears black, creating a negative of the light areas of the scene.

When the film was exposed in the camera, light struck the silver-halide crystals suspended in the emulsion, leaving tiny invisible latent-image specks.

Light forming latent-image specks on silver-halide crystals

During development, each exposed crystal is amplified from its latent speck into a tangled grain of metallic silver.

A latent speck developing into a filamentary silver grain

How light affects density:

• Areas that received more light become denser with metallic silver.
• Areas that received no light remain as silver halides, which will be removed later.

Development time & temperature

Development time depends on:

• The type of developer used (strength & formula).
• The temperature of the chemicals.
• The film stock being developed.

Films with different times cannot share a tank

Develop two films together only if they need the same time in your developer.

Finding your development time

• The film's box or datasheet: most list times for common developers. Ilford publish theirs online.
• Our developing time calculator: times for many film and developer pairs, adjusted for temperature and agitation.
• A development test: for films with no published time.

Adjusting for temperature

Times are for 20°C. If your developer is warmer or cooler:

1. Measure the developer's temperature.
2. Look up the new time in Ilford's temperature compensation chart, or enter the temperature in the calculator. It also warns you when the developer is too hot.

Agitation

Agitation moves fresh developer over the film. Without it, the developer touching the film wears out and the negatives develop unevenly.

By hand

At home, use Ilford's inversion method:

1. Turn the tank upside down and back four times in the first 10 seconds.
2. Repeat four inversions in the first 10 seconds of every minute after that.

Published development times assume hand agitation like this, so use them as they are.

In a rotary processor

Many darkrooms, ours included, use rotary processors. A rotary processor turns the tank continuously, so fresh developer reaches the film all the time. Development runs faster than by hand, and too much agitation also raises contrast.

• Reduce the development time by 15%. For example, 10 minutes by hand becomes 8 minutes 30 seconds.
• The developing time calculator can make this adjustment for you.

2. Stop

Once development is complete, the process must be stopped immediately to prevent overdevelopment. This is done using a stop bath or water rinse. Stop bath is often a citric acid solution which lowers the pH, halting development and extending the life of the fixer by reducing contamination.

Stop time & temperature

• Standard time: 1 minute for fresh stop bath
• Required temperature: similar to developer
• Agitation: Continuous or 10 seconds every 30 seconds

Alternatively, if no stop bath is available, multiple rinses of clean water can be used.

3. Fix

Fixing dissolves the silver halide that was never exposed, so the film stops reacting to light. Before fixing, film looks milky or cream-coloured. Once fixed, the clear areas are clear.

Fix time & temperature

• Standard time: 5 to 7 minutes, depending on the fixer's strength
• Required temperature: similar to developer
• Agitation: Continuous or 10 seconds every 30 seconds

If the clear areas still look milky after fixing, the film is under-fixed. Put it back in the fixer for a few more minutes.

Checking your fixer

Snip the end off a film leader and drop it in a little fixer. Time how long it takes to turn clear. Fix your film for twice that time. When the clearing time is double what it was with fresh fixer, replace it.

If the negatives look wrong

• Clear film with no edge markings: the developer did not work. It may be exhausted, or the fixer went in first.
• Small clear round spots: air bubbles stuck to the film. Tap the tank after pouring in the developer.
• Streaks near the sprocket holes: agitation was too vigorous.
• One end of the film thinner than the other: too little developer to cover the reel.
• Milky patches: under-fixed. Fix again.

Exposure problems are covered in reading your first negatives.