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Sandpaper
Sandpaper (or sanding paper)
is a heavy paper
coated with sand or other abrasive
material
and has three uses:
- to remove materials
- to smooth materials
- or to prepare them to receive an additional
coat.
Sandpaper works by scratching and removing
tiny bits from the surface of the material
against which it is rubbed. Sandpaper with
high abrasion and applied with sufficient
force will remove significant amounts of
material (like a file would), and so one
can use the flexible quality of sandpaper
to even out surfaces, round corners, or make
indentations. If one sands with sandpapers
of progressively smaller grit (that's the
number of sanding particles per square inch),
the papers create smaller and smaller scratches
and thus the feel and appearance of a smoother
surface. In some cases, such as between coats
of polyurethane or when applying paint to
an already glossy surface, it is necessary
to use sandpaper to "scratch up"
the surface so that the top coat can lock
into the scratches in the existing coat.
Grit Size
Sandpaper's abrasive strength is labeled
by "grit," which is the number
of abrasive particles per square inch. As
the grit gets higher, the particles get smaller,
and so the sandpaper's ability to make large
scratches declines. Sandpaper grits range
from 40 to 600 and correspond to designations
of "course" to "super fine."
Choosing the Right Sandpaper
In addition to grit size, you
should consider
the abrasive material (typically
aluminum
oxide or garnet) and the adhesive
that holds
it to the backing (glue or resin).
Either
type of abrasive is fine for
wood, but choose
aluminum oxide for the any other
material.
A resin binder is better since
it holds better
and will allow the sandpaper
to last longer
under heavy use.
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