Copper toning is a chemical process used to alter the colour of monochrome photographic prints, giving them a warm, reddish or brownish tone. This technique is part of the broader category of photographic toners and is often used to enhance the aesthetic appeal, archival stability, and mood of black-and-white prints. By replacing or modifying the metallic silver in the image, copper toning can create subtle or dramatic colour shifts, depending on the desired effect.