technical: developing black and white film

Preparing chemistry

Measure all the developer, stop and fix you will need and make sure there is the right amount and it is correctly diluted. Usually you need 300mls of each solution, that is, developer, stop, and fix, for each 35mm film to be processed. Some developers are one stop developers and need to be made up fresh each time, while stop and fix can be kept and used again. Check your processing time according to the film and developer you are using. It is essential to be accurate about this, as small differences in developing time can make a big difference to your film. All processing chemistry should be used at 20 degrees C; again, even a small difference in the temperature of the developer will make a big difference to your film.


a picture of chemicals being poured from a measuring cylinder into a developing tank

Pour the developer into the tank and start timing immediately. Replace water tight lid. Tap the tank on a solid surface to dislodge air bubbles that might be stuck to the film. Agitate by inverting the tank twice every minute, or half minute; depending on what developer you are using, to ensure the film is always in contact with fresh developer inside the tank. At this point silver halides in the film that have been exposed to light are being be converted to particles of metallic silver that make up the photographic image. When the time is up pour out the developer. This should later be disposed of in a responsible way, or stored for further use in a labeled container.

animation: the twisting motion required to correctly agitate chemicals in the developing tank


Stop is a solution of acetic acid, which immediately halts development. Pour this into the tank, agitate for half a minute, then pour out and store in a labeled container.


Fix dissolves unexposed silver halides, making the image permanent. The fix should be poured into the tank and agitated every half minute for at least 3 minutes. If you open the tank and the film looks cloudy, it needs further fixing. Store fix that can be used again in a labeled container.


Film must be washed carefully for at least 20 minutes. Water temperature should be 20 degrees C - any extremes in temperature can permanently damage film. A wetting agent can be used but is not essential. You can take the film off the reel, and place in the sink as shown, or leave film on the reel in the tank, with a hose running through the middle of the tank.

a picture of film being washed in a sink and hung to drip-dry


A negative dryer is useful to dry film quickly and keep it clean. Hang film up, switch dryer on and leave it for 30 minutes. As film dries the emulsion goes sticky so avoid handling film before it is completely dry. If you do not have a dryer, hang film on a line in a dust free room. Don't use a fan heater as these blow dust around, and don't put film in the airing cupboard, as these are usually full of fluff which will stick to your film.


Cut 35mm negs into strips of 6 and store in neg filing sheets. Handle with care and keep them clean. Your negs are unique and cannot be replaced or reproduced.