introduction
ISO (International Organization for Standardization) is a global alliance of national standards bodies (ISO member bodies). The development of international standards is usually carried out through ISO technical committees. Each member institution interested in a subject on which a technical committee has been established has the right to be represented on that committee. International governmental and non-governmental organizations liaising with ISO are also involved in this work. ISO works closely with the International Electrotechnical Commission (IEC) on all matters of electrical standardization.

The procedures used to develop this document and those used for further maintenance are described in Part 1 of the ISO/IEC Directive. In particular, attention should be paid to the different approval criteria required for different types of ISO documents. This document has been drafted in accordance with the editing rules of ISO/IEC Directive Part 2 (see iso.org/directives).

Please note that certain elements of this document may be subject to patent rights. ISO is not responsible for identifying any or all such patents. Details of any patent rights identified during the preparation of the document will be found in the introduction and/or in the list of patent claims received by ISO (see iso.org/patents).

ISO 12625-7-2021 “Tissue paper and tissue paper products – Determination of optical properties – Part 7 Measurement of brightness and chroma using D65/10° (outdoor daylight)”

Any trade names used in this document are provided for the convenience of the user and do not constitute an endorsement.

Voluntary, related standards and conformity assessment related ISO specific and express the meaning of terminology as well as in relevant ISO technical barriers to trade (TBT) adhere to the principle of the world trade organization (WTO) information, please refer to the iso.org/iso/foreword.html.

This document has been prepared by the Technical Committee ISO/TC 6 (Paper, board and pulp), SC 2 Subcommittees (Test methods and quality specifications for paper and paperboard) in collaboration with the Technical Committee CEN/TC 172 (Pulp, paper and paperboard) of the European Committee for Standardization (CEN). In accordance with the Technical Cooperation Agreement between ISO and CEN (Vienna Agreement).

The third edition cancels and replaces the second edition (ISO 12625-7:2014), which has been technically revised.

The main changes from the previous edition are as follows:

– Alternative formulas in 11.2.1 have been removed because they are not related to tissue paper.

A list of all parts in the ISO 12625 series can be found on the ISO website.

ISO 12625-7-2021 “Tissue paper and tissue paper products – Determination of optical properties – Part 7 Measurement of brightness and chroma using D65/10° (outdoor daylight)”

Any feedback or questions regarding this document should be directed to the user’s national standards body. A complete list of these institutions can be found at iso.org/members.html.

introduce
Brightness and chrominance measurements can be made under a variety of lighting and viewing conditions. This document deals with D65/10° conditions, which refer to outdoor daylight.

ISO 12625-15 takes into account the C/2° condition (indoor daylight). While both international standards deal with brightness and color, the results obtained are often different and uncorrelated.

Optical measurement is affected by the geometry of the instrument used and the texture of the material. The instrument design used in accordance with this document and the routines used for calibration are specified in ISO 2469 and ISO 11475.

Optical properties are related to the visual appearance of the material. Therefore, although optical properties are inherent to tissue paper, they are not functional properties.

Luminance should not be confused with an optical property called CIE whiteness, which is based on reflectance data obtained over the entire visible spectral range (VIS), while luminance measurements are limited to the blue region of the VIS.

ISO 12625-7-2021 “Tissue paper and tissue paper products – Determination of optical properties – Part 7 Measurement of brightness and chroma using D65/10° (outdoor daylight)”

Because of its importance to some countries, three different test methods have been developed to determine the optical properties:

– This document, 12625-7.ISO;

—ISO 12625-15;

– ISO 12625-16.

1 Range
This document specifies an instrumental test procedure for determining the brightness and color of tissue paper and tissue products observed under outdoor daylight conditions. It also provides specific instructions for the preparation of specimens (single layer, multi-layer products) and the optical measurement of products, where special precautions may be required.

Note that properties called ISO brightness and chroma at C/2° (indoor daylight) are measured using instruments adjusted to much lower UV content than specified in this document. ISO 12625-15 describes ISO brightness and chromaticity measured using C/2° (indoor daylight).

ISO 12625-7-2021 “Tissue paper and tissue paper products – Determination of optical properties – Part 7 Measurement of brightness and chroma using D65/10° (outdoor daylight)”

2 Normative references
The following files are referenced in text in a manner that constitutes part or all of the requirements of this document. For dated references, only the cited version applies. For undated references, a new version of the reference (including any revisions) applies.

ISO 186, Paper and board – sampling to determine average quality

ISO 187, Paper, board and pulp – Standard atmospheres for conditioning and testing and procedures for monitoring sample atmospheres and conditioning

ISO 2469, Paper, board and pulp – Measurement of diffuse reflectance coefficient (diffuse reflectance coefficient)

ISO 4094, Paper, Board and Pulp – General requirements for laboratory capabilities authorized to publish Level 3 optical reference transfer standards

ISO 11475:2017, Paper and board – Determination of CIE whiteness, D65/10 degrees (outdoor daylight)

ISO/CIE 11664-4, colorimetric method – Part 4: CIE 1976 L*a*b* Color space

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

3.1 Diffuse reflection radiation coefficient R

The ratio of radiation reflected and emitted from an object to radiation reflected from a good reflection diffuser under the same diffuse illumination and normal detection conditions

Note 1: The ratio is usually expressed as a percentage.

[Source: ISO 2469:2014, 3.2]

3.2 Inherent diffuse reflection radiation coefficient R∞

The diffuse reflection radiation coefficient (3.1) of thickness to an opaque material layer or pad, i.e. increasing the thickness of the pad by doubling the amount of paper, results in no change in the measured radiation coefficient

ISO 12625-7-2021 “Tissue paper and tissue paper products – Determination of optical properties – Part 7 Measurement of brightness and chroma using D65/10° (outdoor daylight)”

Note 1: The radiation coefficient of a single opaque sheet depends on the background, not the material properties.

Note 2: The ratio is usually expressed as a percentage.

[Source: ISO 2469:2014, 3.3]

3.3 Reflectivity coefficient

The flux reflected in the direction of a given cone with its vertex at a surface element is the quotient of the flux reflected in the same direction by a reflection diffuser equally irradiated or illuminated

Note 1: The ratio is usually expressed as a percentage.

Note 2: This term should only be used when the test material is known not to emit light (fluorescence).

[Source: CIE S 017 ILV: 2020, 17-24-070]

ISO 12625-7-2021 “Tissue paper and tissue paper products – Determination of optical properties – Part 7 Measurement of brightness and chroma using D65/10° (outdoor daylight)”

3.4D65 brightness

The inherent diffuse radiation coefficient (3.2) is measured using a reflectormeter with the characteristics described in ISO 2469, equipped with a filter with an effective wavelength of 457nm (half-bandwidth of 44nm) or corresponding function, and adjusted so that the UV content of the radiation incident on the sample under test corresponds to the UV content of the CIE standard light source D65

Note 1: The weighting factors given in ISO 2470-2 describe the filtering function more fully.

3.5 tristimulus value

X 10, Y 10, Z 10

In a given three-color system, the amount of reference color stimulus is needed to match the color of the stimulus under consideration

Note 1: In ISO 5631-2, the CIE standard light source D65 and the CIE 1964 (10°) standard observer are used to define the tricolor system.

Note 2: Subscript 10 is used to conform to the CIE convention that when using the CIE 1964 (10°) standard colorimetric viewer, the tristimulus unit has subscript 10.

[Source: CIE S 017 ILV: 2020, 17-23-038]

ISO 12625-7-2021 “Tissue paper and tissue paper products – Determination of optical properties – Part 7 Measurement of brightness and chroma using D65/10° (outdoor daylight)”

3.6 Color (D65/10°)

Based on the L*, a*, and b* values of the CIELAB 1976 system sample described in ISO/CIE 11664-4, Corresponding to the CIE standard light source D65 described in ISO 11664-2 and the CIE 1964 standard colorimetric viewer described in ISO/CIE 11664-1, determined by measurement under the conditions specified in ISO 5631-2

Note 1: The quantity L* is a measure of the brightness of the test piece, where L* = 0 corresponds to black and L* = 100 is defined by a good reflection diffuser. Visually, the quantities a* and b* represent the red-green and yellow-blue axes in the color space, respectively, such that

– +a* is a measure of the redness of the test piece,

— -a* is a measure of the greenness of the test piece.

– +b* is a measure of the degree of yellowing of the test piece,

– -b* is a measure of the blueness of the test component, and

– If both a* and b* are equal to zero, the specimen is gray.

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