This test method covers
a procedure for rapid, inexpensive determination of the film hardness of
an organic coating on a substrate in terms of drawing leads or pencil leads
of known hardness. The test is especially useful in developmental
work and in production control testing in a single laboratory. Obviously,
the results may be inconsistent from one operator to another because we
all know we push our pencils at different pressures.
A coated panel such as
that in many ASTM Standard Tests is placed on a firm horizontal surface
such a laboratory bench. The pencil is held at a 45o angle
and pushed away from the operator in a 1/4 inch (6.5 mm) stroke.
The process is repeated from the hardest lead to the softest lead to reveal
which the hardness of the coating. Below is a depiction of an actual
pencil hardness test on a metal panel. One can see the various lines
formed in the coating when scratched by the pencil lead.
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