After having presented the "hierarchy" of exterior paint
surface conditions--from a mild condition such as mildewing which
simply requires cleaning prior to repainting to serious conditions
such as peeling and alligatoring which require total paint removal--one
important thought bears repeating: if a paint problem has been
identified that warrants either limited or total paint removal,
the gentlest method possible for the particular wooden element
of the historic building should be selected from the many available
methods.
The treatments recommended--based upon field testing as well as
onsite monitoring of Department of Interior grant-in-aid and certification
of rehabilitation projects--are therefore those which take three
overriding issues into consideration (1) the continued protection
and preservation of the historic exterior woodwork; (2) the retention
of the sequence of historic paint layers; and (3) the health and
safety of those individuals performing the paint removal. By applying
these criteria, it will be seen that no paint removal method is
without its drawbacks and all recommendations are qualified in
varying degrees.
Methods for Removing Paint
After a particular exterior paint surface condition has been identified,
the next step in planning for repainting--if paint removal is
required--is selecting an appropriate method for such removal.
The method or methods selected should be suitable for the specific
paint problem as well as the particular wooden element of the
building. Methods for paint removal can be divided into three
categories (frequently, however, a combination of the three methods
is used). Each method is defined below, then discussed further
and specific recommendations made:
Abrasive--"Abrading" the painted surface by manual and/or
mechanical means such as scraping and sanding. Generally used
for surface preparation and limited paint removal.
Thermal--Softening and raising the paint layers by applying heat
followed by scraping and sanding. Generally used for total paint
removal.
Chemical--Softening of the paint layers with chemical strippers
followed by scraping and sanding. Generally used for total paint
removal.
Abrasive Methods (Manual)
If conditions have been identified that require limited paint
removal such as crazing, intercoat peeling, solvent blistering,
and wrinkling, scraping and hand sanding should be the first methods
employed before using mechanical means. Even in the case of more
serious conditions such as peeling--where the damaged paint is
weak and already sufficiently loosened from the wood surface --scraping
and hand sanding may be all that is needed prior to repainting.
"Exterior Paint Problems" an Historic Preservation Brief
