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IRREGULAR, SHELL-LIKE CUT
Draw a straight line through the best estimate of the centre of the
irregular cut edge using the graticule scale. This will give a mean
value for thickness.
POOR ADHESION (GIVES THE ILLUSION OF TOO LITTLE
FILM THICKNESS)
Despite the fact that the coating may have fractured at point 'x',
always measure distance 'A' to obtain the thickness of the
coating (single layer of coating in this example).
NO SEPARATION
When measuring the thickness of clear varnish on wood, there
may be no visible demarcation between the coating and the
substrate. If this is the case, soak the exposed wood grain with
a dye solution (fountain pen ink). The coating will not absorb any
dye, but the wood cells do. This enables the cut width to be
measured.
Cutter knife
coating
substrate
A
x
Cutter knife
coating
wood substrate
9
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