BS EN 927-13:2019 pdf free.Paints and varnishes – Coating materials and coating systems for exterior wood.
6.1 Wood panels
Boards of Norway spruce (Picea abies [U. Karst) are selected with normal growth rate (i.e. 3 annual rings to 8 annual rings per 10 mm), a density between 0,4 g/cm3 and 0,5 g/cm3 (measured after conditioning) and straight grain. The wood shall be free from blue stain and evidence of surface or bulk fungal infection. Abnormal porosity (caused by bacterial attack) shall be avoided (see EN 927-3:20 19, A 10). From these boards, panels with the minimum dimensions 170 mm x mm. 70 mm x (20 ± 2) mm free from knots, cracks and resinous streaks are produced so that the inclination of the growth rings to the test surface is 60° to 90°. The panels shall be planed to a smooth and uniform finish. In order to avoid aged wood surface, the panels shall be hand sanded (mesh 150) immediately before coating.
The wood shall be conditioned at (20 ± 2) °C and a relative humidity of (65 ± 5) % in accordance with Iso 554 to an equilibrium moisture content of (13 ± 2) %. After conditioning wood density is determined according to ISO 13061-2.
6.2 Coating application
For each system, select three panels on a random basis from the available supply. Apply the coating system to the front side of one panel using the method specified by the manufacturer to give a wet film thickness corresponding to the mean value ± 20% of the manufacturer’s recommended spreading rate. Record the quantity of coating applied. The values should be stated preferably in grams per square metre, but may also be expressed as wet film thickness (in micrometres).
After coating application, age the panels for 21 days in the controlled environment at (20 ± 2) °C and a relative humidity of (65 ± 5) % in accordance with ISO 554.No impact point shall be less than 15 mm from any edge of the test panel. The centres of impact points shall not be less than 15 mm apart. If the grid pattern method detailed in 6.3.2 is to be used, then eight lines spaced at least 15 mm apart shall be marked out on the surface that is to be tested. The lines shall be perpendicular to the direction of grain. Three impact points spaced at least 15 mm apart shall be marked off along each line (see Figure 2).BS EN 927-13 pdf download.