Acid rinse is a mild acidic solution applied to photographic film or paper immediately after development and before fixation. Its primary function is to neutralize any residual alkaline developer left on the emulsion, effectively stopping further development and preventing overexposure or uneven contrast. Using an acid rinse helps maintain consistent tonal quality, improves the stability of the image, and prepares the material for proper fixation. Acid rinses are an important step in black-and-white darkroom processing, contributing to sharper, cleaner negatives and prints with improved archival longevity.