VARNISH HARDNESS - GB/T6739-2006 (adapted)

1. TOOLS
1.1 A set of drawing pencils: 9H, 8H, 7H, 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B, 4B, 5B, 6B, 7B,
     8B, 9B
1.2 A pencil sharpener
1.3 400# soft sandpaper
1.4 A pencil carrying trolley (optional)
1.5 Gauze or cotton for medical use or an eraser

2. SAMPLING
We sample in accordance with ISO 1512:1974 Sampling of Paints and Varnishes - neq GB 3186
Sampling of Coated Products

3. ENVIRONMENTAL CONDITIONS
Temperature: 23 (+/-2)℃ 
Humidity: 50 (+/-5)%

4. TESTING PROCEDURE
4.1 We sharpen the pencil until we obtain a graphite tip of about 5 mm-6 mm



4.2 We abrade the graphite tip at a 90º angle with 400 # soft sandpaper



4.3 We place the test sample on a level surface
4.4 We adjust the pencil onto a pencil trolley and lay the pencil tip onto the test sample
4.5 We slide the pencil away at a 45º angle and at a speed of 0.5 -1 mm/s, drawing a minimum 7 mm line



4.6 We repeat the procedure (4.1-4.5) 5 times with the same pencil
4.7 We erase the pencil drawing in order to expose any scratches on the varnish surface

5. ASSESSING TEST RESULTS
5.1 We use a low hardness pencil to start the test
5.2 Normally, low hardness pencils will not cut through the varnish
5.3 We continue performing the test with increasingly harder pencils
5.4 We identify the pencil which is hard enough to cut at least a 3 mm long scratch through the varnish
5.5 We then determine the varnish hardness is one level below that of the pencil which cut through the varnish (see 5.4 above)