Light Fastness Fabric

These are a series of 8 wool fabrics dyed with specified blue dyes to give blue wool cloths ranging from very low light fastness, to very high light fastness. They form a numerical scale of 1 to 8 where 1 has the poorest light fastness to 8 which has the best light fastness. This allows fabrics to be graded, using a grey scale for change in colour, for correlation with performance in use. They are used in the ISO 105 B series of tests.