1.1 This test method determines the brightness of white, near-white, and naturally colored pulp, paper, and paperboard. Brightness is a commonly used industry term for the numerical value of the reflectance factor of a sample, with respect to blue light of specific spectral and geometric characteristics. This test method requires an instrument employing 45° illumination and 0° viewing geometry, with the illuminating and viewing beams adjusted so that translucent materials are evaluated on an arbitrary but specific scale (1-4).

1.2 This test method is applicable to all naturally-colored pulps, and papers and board made from pulps. The measurement is not suitable for paper and paperboard containing added coloring matter (such as yellow or green dyestuff) which appreciably absorbs light in that part of the spectrum extending from about 400 to 500 nm. Colored papers must be measured spectrophotometrically or colorimetrically in order to obtain meaningful results (TAPPI T442, T524, and T527). This test method is, however, suitable for pulps or papers which contain optical (fluorescent) brightening agents.

1.3 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.