During film development, what is the purpose of the stop bath?

The purpose of the stop bath in film development is to halt the developing process. After the film has been immersed in the developer solution for a specific duration, it needs to be stopped from further developing to prevent overexposure and to ensure that the image is fixed as intended. The stop bath is typically a weak acid solution, such as acetic acid diluted with water, which quickly neutralizes the developer chemicals still in contact with the film. This prevents the development from continuing and helps stabilize the image created during the developing phase. The stop bath effectively preserves the qualities of the exposure before moving on to the next stage, which is usually the fixer.