To make the latent image visible, the film must undergo a chemical process known as development. Here’s a step-by-step guide to the main stages of black and white film development:

1. Developer The developer is the first and most critical chemical used in the process. It consists of a reducing agent, typically a substance called Metol or hydroquinone, mixed with an alkaline solution. The developer reacts with the exposed silver halide crystals on the film, reducing them to metallic silver. The more light that has struck a particular area of the film, the more silver is produced, resulting in various shades of gray. Unexposed areas remain unaffected and will later become the white or light areas of the image.

2. Stop Bath After a predetermined amount of time in the developer, the film is transferred to the stop bath. The stop bath is a weakly acidic solution that halts the development process by neutralizing the alkaline developer. This step is crucial to prevent overdevelopment and maintain the proper balance of tones in the final image.

3. Fixer Next, the film is placed in the fixer solution. The fixer’s primary purpose is to remove any unexposed silver halide crystals that did not react with the developer. The fixer contains chemicals like sodium thiosulfate or ammonium thiosulfate, which dissolve the remaining silver halide crystals, making the film no longer light-sensitive. This step ensures that the image will not continue to develop when exposed to light and stabilizes the final result.

4. Washing After fixing, the film is thoroughly washed with water to remove any residual chemicals. This step is essential to ensure the long-term stability and quality of the developed film.

5. Drying Finally, the film is dried, typically by hanging it in a dust-free environment. Once completely dry, the film can be cut and placed in protective sleeves or used to make prints or enlargements.