ASTM International

Standard Test Methods for Lightfastness of Colorants Used in Artists’ Materials
 N D4303

Annotation

Four test methods to accelerate the effects of long term indoor illumination on artists’ materials are described below. One of the natural daylight methods and one of the xenon-arc methods are used to categorize the lightfastness of colorants.

Test Method A—Exposure in southern Florida to natural daylight filtered through window glass.

Test Method B—Exposure in Arizona to natural daylight filtered through window glass.

Test Method C—Exposure in a non-humidity controlled xenon-arc device simulating daylight filtered through window glass.

Test Method D—Exposure in a humidity controlled xenon-arc device simulating daylight filtered through window glass.

These test methods are used to approximate the color change that can be expected over time in colorants used in artists’ materials exposed indoors to daylight through window glass.

NOTE 1—The color changes that result from accelerated exposure may not duplicate the results of normal indoor exposure in a home, art gallery, or museum. The relative resistance to change, however, can be established so colored materials can be assigned to categories of relative lightfastness.

NOTE 2—Users who wish to test colored materials under fluorescent illumination should consult Practice D4674.

Lightfastness categories are established to which colorants are assigned based on the color difference between specimens before and after exposure.

Color difference units are calculated by the CIE 1976 L*a*b* color difference equation.