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. This forms 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 Color, for correlation with performance in use. This is used to predict the suitability for a given end use; typically apparel would be a minimum of grade 4 whilst furnishings would require a grade 6. They are used in the ISO 105 B series of tests and can be used in conjunction with the Humidity Control fabric for machine calibration.
To complement the range of Blue Wool Standards we also supply specially prepared mounted card that is totally free of any optical brightening agents. This ensures mounted samples are easier to grade as the card does not show a significant Color change. It is widely recognized that the Color of the background can influence how an item is finally graded.