AATCC 16-2004 Colorfastness to Light.
2.1 Samples of the textile material to be tested and the agreed upon comparison standard(s) are exposed simultaneously to a light source under spccified conditions. The colorfastness to light of the specimen is evaluated by comparison of the color change of the exposed portion to the masked control portion of the test specimen or unexposed original material using the AATCC Gray Scale for Color Change, or by instrumental color measurement. Lightfastness classification is accomplished by evaluation versus a simultaneously exposed series of AATCC Blue Wool Lightfastness Standards.
3.1 AATCC Blue Wool Lightfastncss Standard. n.—one of a group of dyed wool tbrics distributed by AATCC for use in determining the amount of light exposure of specimens during Iightfastness testing (sec 32.1).
3.2 AATCC Fading Unit (AFU), n.— a specific amount of exposure made under the conditions specified in various test methods where one AFU is one- twentieth (1/20) of the light-on exposure required to produce a color change equal to Step 4 on the Gray Scale for Color Change or 1.7 * 0.3 CIEL.AB units of color difference on AATCC Blue Wool Lightfastness Standard L4.
3.3 black-panel thermometer. n.—a tcmpcraturc measuring device, the sensing unit of which is coated with black paint designed to absorb most of the radiant energy encountered in lightfastness testing (see 32.2).
3.3.1 This device provides an estimation of the maximum temperature a specimen may attain during exposure to natural or artificial light. Any deviation from the gcomeuy of this device described in 32.2 may have an influence on the measured temperature.
3.4 black standard thermometer, n.—a temperature measuring device, the sensing unit of which is coated with black material designed to absorb most of the radiant energy encountered in lightfastness testing and is thermally insulated by means of a plastic pLate (see 32.2).
3.4.1 This device provides an estima
tion of the maximum temperature a specimen may attain during exposure to natural or artificial light. Any deviation from the geometry of the device described in 32.2 may have an influence on the measured temperature. The temperature measured by the black standard thermometer will not be the same as that measured by the black-panel thermometer; therefore, they cannot be used interchangeably.
3.5 broad bandpass radiometer. n.— a relative term applied to radiometers that have a bandpass width of more than 20 nm at 50% of maximum transmittance and can be used to measure irradiance at wavelengths such as 300-400 nm or 300-800 nm.
3.6 color change, n.—as used in colorfastness testing, a change in color of any kind whether a change in lightness, hue or chroma or any combination of these, discernible by comparing the test specimen with a corresponding untested specimen.AATCC 16 pdf download.