Different chemicals are used to develop film, and the ingredients each have a specific purpose. To develop film, there are definite steps that must be taken to get the film to the developing stage--from using a changing bag or a light-safe room to placing undeveloped film into a developing tank and beginning the developing process. The chemicals, though, are the key.
Developer
This chemical develops the image captured on the film. One of the most popular brands for black and white film developing is Kodak's D-76. Its composition is typically metol, sodium sulfite, boric acid and hydroquinone all diluted in water. Several manufacturers have a developer similar to Kodak's.
Stop Bath
This chemical is an agent that stops the developer from working. It's typically a diluted solution of acetic acid, although plain water will also put the developing process to a stop.
Fixer
This chemical "fixes" the image to make it safe to expose to light while making the captured image permanent on the film. It's composed of the chemicals sodium thiosulfate or ammonium thiosulfate.
Water
After the fix stage, you need to wash the film to remove all the fixing chemicals and keep the film from being ruined. There's nothing better to do this with than water from the tap.
Wetting agent
Often referred to as "photo flo," this chemical keeps water from leaving marks on the film during the drying process.
Air
Once the film is developed, it's time to dry the film. Most darkrooms should have some form of cabinet that allows film to dry with either forced oxygen or by just sitting there--but the cabinet protects the film from gathering dust.
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