This part of ISO 12625 specifies testing procedures for the instrumental determination of the optical properties of tissue paper and tissue products. The available testing procedures are currently or are in the process of becoming International Standards. These are listed and outlined in Annex C.
Furthermore, this part of ISO 12625 gives recommendations regarding the measurement of the opacity and the intrinsic diffuse blue radiance factor (D65 brightness) for different types of tissue paper and tissue products and issues specific instructions for the preparation of samples (single layer and multi-layer products), as well as the optical measurement of creped and stamped products, where special precautionary measures may be required if the surface of the samples is irregular or if the material is particularly voluminous, so that air may be entrapped between the sheets.