If hand sanding for purposes of surface preparation has not been
productive or if the affected area is too large to consider hand
sanding by itself, mechanical abrasive methods, i.e., poweroperated
tools may need to be employed; however, it should be noted that
the majority of tools available for paint removal can cause damage
to fragile wood and must be used with great care.
Brief 06 - Abrasive Cleaning
Recommended Abrasive Methods (Mechanical)
Orbital sander: Designed as a finishing or smoothing tool--not
for the removal of multiple layers of paint--the orbital sander
is thus recommended when limited paint removal is required prior
to repainting. Because it sands in a small diameter circular
motion (some models can also be switched to a backandforth vibrating
action), this tool is particularly effective for "feathering"
areas where paint has first been scraped (see figure 11). The
abrasive surface varies from about 3x7 inches to 4x9 inches
and sandpaper is attached either by clamps or sliding clips.
A medium grit, opencoat aluminum oxide sandpaper should be used;
fine sandpaper clogs up so quickly that it is ineffective for
Belt sander: A second type of power tool--the belt sander--can
also be used for removing limited layers of paint but, in this
case, the abrasive surface is a continuous belt of sandpaper
that travels at high speeds and consequently offers much less
control than the orbital sander. Because of the potential for
more damage to the paint or the wood, use of the belt sander
(also with a medium grit sandpaper) should be limited to flat
surfaces and only skilled operators should be permitted to operate
it within a historic preservation project.
Rotary Drill Attachments: Rotary drill attachments such as
the rotary sanding disc and the rotary wire stripper should
be avoided. The disc sander usually a disc of sandpaper
about 5 inches in diameter secured to a rubber based attachment
which is in turn connected to an electric drill or other motorized
housing can easily leave visible circular depressions
in the wood which are difficult to hide, even with repainting.
The rotary wire stripper clusters of metals wires similarly
attached to an electric drill-type unit can actually
shred a wooden surface and is thus to be used exclusively for
removing corrosion and paint from metals.
Waterblasting: Waterblasting above 600 p.s.i. to remove paint
is not recommended because it can force water into the woodwork
rather than cleaning loose paint and grime from the surface;
at worst, high pressure waterblasting causes the water to penetrate
exterior sheathing and damages interior finishes. A detergent
solution, a medium soft bristle brush, and a garden hose for
purposes of rinsing, is the gentlest method involving water
and is recommended when cleaning exterior surfaces prior to
Sandblasting: Finally and undoubtedly most vehemently
"not recommended" sandblasting painted exterior
woodwork will indeed remove paint, but at the same time can
scar wooden elements beyond recognition. As with rotary wire
strippers, sandblasting erodes the soft porous fibers (spring
wood) faster than the hard, dense fibers (summer wood), leaving
a pitted surface with ridges and valleys. Sandblasting will
also erode projecting areas of carvings and moldings before
it removes paint from concave areas. Hence, this abrasive method
is potentially the most damaging of all possibilities, even
if a contractor promises that blast pressure can be controlled
so that the paint is removed without harming the historic exterior
woodwork. (For Additional Information, See Preservation Briefs
6, "Dangers of Abrasive Cleaning to Historic Buildings".)
Summary of Abrasive Methods (Mechanical)
Recommended: Orbital sander, belt sander (skilled operator
Applicable areas of building: Flat surfaces, i.e., siding, eaves,
doors, window sills.
For use on: Class II and Class III conditions.
Health/Safety factors: Take precautions against lead dust and
eye damage; dispose of lead paint residue properly.
Not Recommended: Rotary drill attachments, high pressure waterblasting,