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 well-ventilated areas. Safer strippers, made with dibasic
acid esters and other chemicals, such as biodegradable
citrus derivatives, are now available.
Blanket or mat-type strippers are similar to leach
packs, but they have the advantage of containing the paint
residue after it is removed so that disposal is simpler
and safer.
Lime washes, such as whitewash, can be dissolved in
acids.
o Mechanical Means. Careful hand sanding and scraping are
often good ways of removing paint. Belt sanders, rotary
wire brushes, and power-driven carbide cones and discs
should not be used on historic buildings. Sanding and
scraping, even by hand, can create dust containing toxic
materials such as lead. They require the use of masks and
careful cleanup.
4.4.2 Masonry Coatings and Paint. Waterproof or water-
repellent coatings or other treatments should not be used unless
necessary to solve a specific problem that has been studied and
identified. The coatings are often expensive and unnecessary,
and they do not stabilize masonry by preventing further
Waterproof coatings seal the surface of masonry against both
water and water vapor. They are intended for use below grade.
Water-repellent coatings, which seal against water but not
against water vapor, should be used above grade. Coatings can
trap moisture within the masonry, causing spalling and other
damage. Silicone sealers (the most commonly used type) may add a
slight sheen to the finish. They must be renewed after 5 to 7
years. They may cause subflorescence (a build-up of mineral
salts beneath the surface of the masonry) , which can lead to
spalling. Only-water soluble solutions (such as silicones and
siliconates) are acceptable for use on historic buildings. Do
not use acrylic or polymeric solutions (acrilates) , polyvinyl
chloride (PVC), or polyvinylacetate.
Paint is a traditional protective coating for brick.
Although it is considered reversible because it can be removed,
its removal can damage the original surface. In general,
historic buildings should not be painted for purely cosmetic
reasons. Built-up paint can obscure important decorative details
and interfere with the masonry's ability to breathe. Often,
cleaning is enough to renew the surface.
Paint can create many of the same problems as other coatings.
Traditional whitewashes (lime washes) allow some vapor
transmission, but there are modern latex paints made especially
for exterior masonry walls that are preferred. Paints such as
epoxies and some alkyds may not allow masonry or wood to breathe
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