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ISO 2471 Opacity




ISO 2471


Determination of opacity (paper backing) — Diffuse reflectance method


ISO 2471 Opacity specifies a method for the determination of the opacity (paper backing) of paper by diffuse reflectance.
It can be used to determine the opacity of papers or boards which contain fluorescent whitening agents, provided the UV content of the radiation incident on the test piece has been adjusted to conform to that in the CIE illuminant C using a fluorescent reference standard provided by an ISO/TC 6 authorized laboratory as described in ISO 2470-1.
This test is not applicable to colored papers or boards which incorporate fluorescent dyes or pigments.


The luminance factor of a single sheet of the paper over a black cavity and the intrinsic luminance factor of the paper are determined. The opacity is calculated as the ratio of these two luminance factor values.

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