7. Procedure
7.1 For wood pencils, remove approximately 5 to 6 mm (3⁄16
to 1⁄4 in.) of wood from the point of each pencil using a
draftsman-type mechanical sharpener, being careful to leave an
undisturbed, unmarked, smooth cylinder of lead. Holding the
pencil holder (when using drawing leads) at an angle of 90° to
the abrasive paper, rub the lead against the paper maintaining
an exact angle of 90° to the abrasive paper until a flat, smooth
and circular cross section is obtained, free of chips or nicks in
the edge of the cross section. For wood pencils, see Fig. 1 for
an illustration. For mechanical pencil holders with drawing
leads, see Fig. 2 as the illustration. The desired edge may be
obtained by cementing the abrasive paper to a flat motor-driven
disk. By supporting the pencil at 90° to the rotating disk a
uniform flat lead end may be obtained more reproducibly.
7.2 Place the coated panel on a level, firm, horizontal
surface. Starting with the hardest lead, hold the pencil or lead
holder firmly with the lead against the film at a 45° angle (point
away from the operator) and push away from the operator.
Exert sufficient uniform pressure downward and forward either
to cut or scratch the film or to crumble the edge of the lead. It
is suggested that the length of the stroke be 6.5 mm (1⁄4 in.).
7.3 Repeat the process down the hardness scale until a
pencil is found that will not cut through the film to the substrate
(either metal or a previous coat) for a distance of at least 3 mm
(1⁄8 in.) (see 8.1.1).
NOTE 1—The operator must watch closely for cutting into or scratching
the film. Some finishes contain compounds that may tend to lubricate the
film. Checks should be made by close visual inspection and by fingernail
feel.
NOTE 2—In conducting the test, if the sharp edge of the lead is slightly
chipped or crumbled, the lead must be resharpened.
7.4 Continue the process until a pencil is found that will
neither cut through nor scratch the surface of the film. Any
defacement of the film other than a cut (gouge) is considered a
scratch. Record each end point (if applicable) for gouge and
scratch hardness (see 8.1).
NOTE 3—With some films, the two end points will be identical.
7.5 Make a minimum of two determinations for gouge
hardness (7.3) and scratch hardness (7.4) for each pencil or
lead.