Standard No.:	GB/T 7974-2013
English Name:	Paper,board and pulps—Measurement of diffuse blue reflectance factor—D65 brightness(Diff/ Geometry,Outdoor daylight conditions)
Chinese Name:	纸、纸板和纸浆 蓝光漫反射因数D65亮度的测定（漫射/垂直法，室外日光条件）
Chinese Classification:	Y30    Papermaking in general
Professional Classification:	GB    National Standard
Source Content Issued by:	AQSIQ;SAC
Issued on:	2013-10-10
Implemented on:	2014-5-1
Status:	valid
Superseding:	GB/T 7974-2002 Paper, board and pulp-Measurement of brightness - Diff/Geometry
Target Language:	English
File Format:	PDF
Word Count:	6000 words
Translation Price(USD):	150.0
Delivery:	via email in 1 business day

1 Scope This standard specifies a method for measuring the D65 brightness of pulps, papers and boards. This standard is applicable to white and near-white papers, boards and pulps, particularly those exhibiting fluorescence which promotes the appearance of whiteness. If the test piece with fluorescent whitening agent is measured, the measurement can only be made in an instrument in which the ultraviolet energy level of the illumination has been adjusted to correspond to the CIE standard illuminant D65 using a fluorescent reference standard. The D65 light source employed in this standard excites almost twice as much fluorescence as the light source in ISO 2470-1: 2009. Consequently, this standard is better suited for measuring the fluorescent contribution to the brightness. Notes: The property called ISO brightness is measured with an instrument adjusted to a much lower UV content than that specified in this standard.D65 brightness should not be confused with ISO brightness which closely approximates the brightness of papers viewed under indoor conditions. The measurement of ISO brightness is described in ISO 2470-1: 2009. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 450 Paper and board - Sampling for testing and identification of machine and cross direction, wire side and felt side (GB/T 450-2008, ISO 186, 2002, MOD) GB/T 740 Pulps - Sampling for testing (GB/T 740-2003, ISO 7213: 1991, IDT) GB/T 7973 Paper, board and pulps - Measurement of diffuse reflectance factor (Diff/ Geometry) (GB/T 7973-2003, ISO 2469: 1994, NEQ) GB/T 8940.2 Pulp - Preparation of laboratory sheets for the measurement of brightness (GB/T 8940.2-2002, ISO 3688: 1999, EQV) GB/T 10739 Paper board and pulp - Standard atmosphere for conditioning and testing (GB/T 10739-2002, ISO 187: 1990, EQV) GB/T 22880-2008 Paper and board - Determination of CIE whiteness, D65/10° (outdoor daylight) (GB/T 22880-2008, ISO 11475: 2004, MOD) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 diffuse radiance factor, R ratio of the radiation reflected and emitted from a body to that reflected from the perfect reflecting diffuser under the same conditions of diffuse illumination and normal detection. The ratio is often expressed as a percentage Note: The diffuse radiance factor is influenced by the backing if the body is translucent. 3.2 intrinsic radiance factor, R∞ radiance factor of a layer or pad of material thick enough to be opaque, i.e. such that increasing the thickness of the pad by doubling the number of sheets results in no change in the measured results 3.3 D65 brightness, R457，D65

Foreword i 1 Scope 2 Normative references 3 Terms and definitions 4 Principle 5 Instruments 6 Sampling 7. Preparation of test pieces 8 Instrument calibration 9 Procedure 10 Expression of results 11 Precision 12 Test report Annex A (Normative) Spectral characteristics of instruments for measuring D65 brightness