BS EN 927 discusses paints and varnishes. BS EN 927‑7 specifies a test method for assessing the discolouration of coating systems on wood due to wood extractives from knots. The discolouration is measured by colourimetry and the result is stated as the colour difference between the coated surface on the knot and the coated surface beside the knot.
BS EN 927‑7 on paints and varnishes is useful for:
The treatment of exterior wood surfaces has both aesthetic and protective functions. A vital purpose of a coating system is to protect against discolouration caused by wood extractives. Discolouration can be characterized as tannin staining or as knot staining.
BS EN 927‑7 provides you with the method for assessment of discolouration of coatings on wood caused by wood extractives in knots, i.e., it relates to knot staining only. The method in BS EN 927‑7 can be used for testing exterior and interior coatings for wood. BS EN 927‑7 helps you to assess the discolouration of coatings on knots.
EN 927-7:2020