7
4 MEASURING FILM THICKNESS
1. Mark the surface to be tested with a stroke of the black
marker pen provided with your gauge. There should always
be a distinct contrast between the colour of the pen ink and
the coating. Different pen ink colours may therefore be
required.
2. Cut the coating at right-angles to the pen mark as follows:
Place the gauge on the specimen (an exact vertical cut
without tilting the knife is ensured by the supporting feet
beside the push button switch).
Pull the gauge towards you and apply a little pressure.
Slight pressure is normally sufficient to penetrate through to
the substrate. Heavier pressure may be required for very
thick coatings and very hard surfaces.
3. Position the gauge so that the microscope lens is over the
cut with the feet touching the surface.
4. Press and hold the light switch to illuminate the cut.
5. Focus the microscope until the cut is clearly visible.
6. Align the graticule scale at right-angles to the cut so that
the scale divisions are parallel to the cut. Note that one side
of the cut will have a straight edge and the other side is
likely to be ragged.
0
20
18
16
14
12
10
8
6
4
2
Exposed
substrate
Cut coating
Coating
(uncut)
Count number of graticule divisions
Pen
mark