VARNISH ADHERENCE - EN ISO 2409:2007 (adapted)
1.1 A single-blade cutting tool with a 20° to 30° edge and a blade thickness of 0.43 mm +/- 0.03 mm; or a multiple blade cutting tool with six cutting edges spaced 2 mm or 3 mm aparts
Regardless of the cutting tool type, when the cutting edge has been worn down to 0.1 mm, it shall be reground
When using a single-blade cutting tool, a series of guiding and spacing edges shall be used in order to space the cuts properly
Pressure-sensitive adhesive tape. In principle, adhesive strength shall between 6 and 10 N per 25 mm width. Minimum width 50 mm
Hand-held lens with x2 or x3 magnifying power
Sample selection per ISO 15528
Sample examination and preparation per ISO 1513
3. ENVIRONMENTAL CONDITIONS
Temperature: 23 (+/- 2) °C
Relative humidity: 50 (+/-) 5%
4. TESTING PROCEDURE
4.1 Condition the test panels immediately prior to the test at a temperature of 23 (+/-2) °C and a relative humidity of 50 (+/-5) % for a minimum of 16 h
4.2 Hold the tool over the sample at 45° angle and effect six cuts in each direction of the lattice pattern. The cuts shall be deep enough to reach the wood substrate. The spacing of the cuts in each direction shall be equal and shall depend on the coating thickness: 2 mm spacing for 61-120 um coating; 3 mm spacing for > 120 um coating
4.3 Brush the sample surface lightly with the soft brush several times forward and backwards along each of the diagonals of the lattice pattern
4.4 When starting a new series of tests, remove two complete laps from a reel of the adhesive tape and discard. Remove an additional length at a steady rate and cut a piece approximately 75 mm long
4.5 Place the centre of the tape over the lattice in a direction parallel to one set of cuts. Smooth the tape into place over the area of the lattice and for a distance of at least 20 mm beyond with a finger. To ensure good contact with the coating, rub the tape firmly with a fingertip or fingernail. The colour of the coating seen through the tape is a useful indication of overall contact
4.6 Within 5 minutes of applying the tape, remove the tape by grasping the free end and pulling it off steadily in 0,5 s to 1,0 s at an angle which is as close as possible to 60 °
5. ASSESSING TEST RESULTS
Immediately after adhesive tape removal, carefully examine the cut area of the test coating, in good lighting, using normal or corrected vision or a lens (as agreed). During the viewing process, rotate the panel so that the viewing and lighting of the test area are not confined to one direction. It can be useful to examine the tape in the same manner
Classify the test area in accordance with the table below
VARNISH ADHERENCE GRID TEST
Test Results Grading
||Illustration of affected
The edges of the cuts are completely smooth; none of the squares of the lattice is detached.
Detachment of small flakes of the coating at the intersections of the cuts. A cross-cut area not greater than 5% is affected.
The coating has flaked along the edges and/or at the intersections of the cuts. A cross-cut area greater than 5%, but not greater than 15%, is affected.
The coating has flaked along the edges of the cuts partly or wholly in large ribbons, and/or it has flaked partly or wholly on different parts of the squares. A cross-cut area greater than 15%, but not greater than 35%, is affected.
The coating has flaked along the edges of the cuts in large ribbons and/or some squares have detached partly or wholly. A cross-cut area greater than 35%, but not greater than 65%, is affected.
||Any degree of flaking that cannot even be classified by classification 4.