Blue Wool Standard

Blue Scales (Textile Fading Cards)

Description

[International Standards Organization] A standard developed in the 1930s by the Society of Dyers and Colourists to characterize lightfastness of materials. The Blue Wool Standard consists of a card that contains eight sections of blue-dyed wool cloth, each with a different lightfastness. The dyes fade at a known rate with each section requiring about twice as much light exposure as the preceding section in order to fade to the same degree. Section ISO 1 is the most fugitive and ISO 8 the most stable. In the absence of ultraviolet light, it takes approximately 400,000 lux hours to cause noticeable fading for the ISO 1 level and 900 million lux hours for the ISO 8 level (Michalski 1990).

The internationally recognized standard is not just used for textiles, but also printing inks, polymers, paints, and artist materials. Testing is usually done in an enclosed laboratory using a Xenon arc lamp, which artificially simulates the exact wavelength and intensity of natural daylight alongside regulated humidity. The material is exposed to light concurrently with a standard blue wool textile card. When the test material's color change matches one of the Blue Wool reference swatches, it receives that corresponding number on the scale James Heal.

Synonyms and Related Terms

Blue Wool Fade Card; ISO Standard R 105; British Standard BS 1006; fading card; norme ISO laine bleue (Fr.)

Resources and Citations

• S. Michalski, "Time's Effects on Paintings" in Shared Responsibilities. National Gallery of Canada, Ottawa, 1990. p.39-53.
• R.L.Feller, R.Johnston-Feller, "Use of the International Standards Organization's Blue Wool Standards for Exposure to Light" AIC Preprints of Papers presented at the 7th Annual Meeting, Toronto, Canada, 1979.
• R. Feller, "Standards in the evaluation of thermoplastic resin" in ICOM committee for Conservation preprints, 5th Triennial meeting, Zagreb. Paris:ICOM, 1978.
• A. Derbiyshire J. Ashley-Smith "A Proposed Practical Lighting Policy for Works of Art on Paper at the V&A" ICOM preprint, Lyon, France, 1999. p.38-41.
• Conservation Support Systems, Catalog, 1997.
• James Heal: Blue Wool Standards - How to Use