What is black when clean and white when dirty?

The concept of "black when clean and white when dirty" typically refers to certain types of clothing or fabrics that appear one color when they are clean and another color when they are dirty.

One example is the traditional white chef's jacket commonly worn in professional kitchens. These jackets are typically made of a white cotton or polyester blend fabric that is designed to show dirt easily. The fabric is chosen intentionally to make it easier for chefs and kitchen staff to identify when their uniform is soiled and needs to be changed or laundered. When the jacket is clean, it appears white, but it quickly accumulates food stains, grease, and other kitchen debris, causing it to appear dirty and off-white.

On the other hand, some clothing items, such as certain types of reusable cloth diapers, may adopt a similar principle but in reverse. Some cloth diapers are made with a special fabric that appears black or dark-colored when they are clean. This helps parents or caretakers to know whether the diaper is soiled or not. When the diaper is wet or dirty, the color changes to a lighter shade or white, indicating that it is time for a diaper change.

These color-changing garments serve the purpose of providing a clear visual indicator of cleanliness or dirtiness, ensuring proper hygiene and maintenance.