Blue Wool Scale

The Blue Wool Scale is a standardized scale used to assess the lightfastness, or resistance to fading when exposed to light, of materials such as dyes and pigments. It primarily consists of a series of blue wool standards that are dyed with specific blue pigments and have a known resistance to fading when exposed to light. The scale typically ranges from 1 to 8: - **1** indicates very poor lightfastness (fades quickly).