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Painting Historic Interiors
Sara B. Chase
The paint Americans used
in the past is undeniably part of a technological and
commercial record. But beyond that, the colors we have chosen
and continue to select for our interior living and working
spaces--bright and exuberant, purposefully somber, or a
combination of hues--reflect our nation's cultural influences
and our individual and collective spirit (see Figures 1, 2).
Paint color is a simple, direct expression of the time, and
of taste, values, and mood. To consider paint only as a
protective coating is to misunderstand its meaning as an
important aspect of America's heritage.
This Brief is about
historic interior paints and choosing new paints for historic
interiors if repainting is necessary or desirable. It
addresses a variety of materials and features: plaster walls
and ceilings; wooden doors, molding, and trim; and metal
items such as radiators and railings. It provides background
information about some of the types of paint which were used
in the past, discusses the more common causes and effects of
interior paint failure, and explains the principal factors
guiding decisions about repainting, including what level of
paint investigation may be appropriate. Careful thought
should be given to each interior paint project, depending on
the history of the building and its painted surfaces.
Treatments may range from protecting extant decorative
surfaces, to ordering custommade paint that replicates the
original paint color, to using today's paint straight off the
shelf and out of the can.
Finally, stripping old
paints or applying new oil/alkyd paints poses serious health
and safety concerns; the State Historic Preservation Officer
should be contacted for current legal and technical
information on removal, disposal, and health and safety
precautions.
Constituents of Historic Paint: Pigment, Binder, and
Vehicle
Paint is a dispersion of
small solid particles, usually crystalline, in a liquid
medium. Applied to a surface, this liquid has the special
quality of becoming a solid, protective film when it dries.
Paint also enhances the appearance of surfaces. A late
Victorian writer observed that the coming of a painter to a
house was cause for celebration. Indeed, these statements not
only indicate the chemical and physical complexity of paint,
but also its emotional impact.
Pigment. Pigment made the
paint opaque, thus preventing deterioration of the substrate
caused by ultraviolet light, and added color, thus making the
paint attractive. White lead, a whitish corrosion product of
lead, was most often used to provide opacity. The white
pigment in a colored paint is often called the "hiding"
pigment. In addition to preventing the sun's damaging rays
from hitting the surface of the substrate, the white lead
also helped prevent the growth of mold and mildew. Not until
early in the 20th century was a successful substitute,
titanium dioxide (TiO2), patented, and even then, it did not
come into prevalent use by itself until the mid20th century
(earlier in the century, titanium oxide and white lead were
often mixed). Zinc oxide was used briefly as a hiding pigment
after 1850 (see Figure 3).
Early tinting pigments
for house paints consisted of the earth pigments--ochres,
siennas, umbers made from iron-oxidecontaining clay--and a
few synthesized colorants such as Prussian blue, or mercuric
sulfide (crimson). From the early 1800s on more pigments were
developed and used to offer a wider and brighter variety of
hues.
Binder. The most common
binder in interior paints was, and still is, oil. Chalk was
sometimes added to waterbased paints to help bind the pigment
particles together. Other common binders included hide glue
and gelatin.
Vehicle. The fluid
component was termed the vehicle, or medium, because it
carried the pigment. Historically, vehicles included
turpentine in oil paints and water in waterbased paints, but
other vehicles were sometimes used, such as milk in casein
paints.
Oil-Based and
Water-Based Paints
The two major types of
paint are termed oilbased and waterbased. For oilbased
paints, linseed oil was frequently chosen because it is a
drying oil. When thinned with an organic solvent such as
turpentine for easier spreading, its drying speed was
enhanced. To make the drying even faster, drying agents such
as cobalt compounds were frequently added. Because the
addition of driers was most successfully done in hot or
boiling oil, boiled linseed oil was preferable. The drying
rate of linseed oil paints was relatively rapid at first, for
several days immediately after application, and paint soon
felt dry to the touch; it is important to remember, however,
that linseed oil paint continues to dry--or more precisely,
to crosslink--over decades and thus continues to a point of
brittleness as the paint ages. Strong and durable with a
surface sheen, oil-based paints were mainly used for wood
trim and metal.
Whitewashes and distemper
paints differed from oil paints in appearance primarily
because the vehicle was water. Waterbased paints were always
flat, having no gloss of their own. Because the paint film
dried to the touch as soon as the water evaporated, driers
were not needed. Waterbase paints were fairly strong, with
the pigments well bound as in hide glue distempers, but they
did not hold up to abrasion. Wood trim, therefore, was rarely
painted with these types of paint historically, though
interior plaster surfaces were frequently coated with
whitewash and calcimine. Distemper paints were commonly used
for decorative work.
Recent Changes to Paint
Constituents. Until the mid20th century, almost all paints
used in America could be divided according to the type of
binder each had. Chemists sought to improve paints,
especially when the two world wars made traditional paint
components scarce and expensive. Modern paints are far more
complex chemically and physically than early paints. More
ingredients have been added to the simple threepart system of
pigment, binder, and vehicle. Fillers or extenders such as
clay and chalk were put in to make oil paints flow better and
to make them cheaper as well. Mildewcides and fungicides were
prevalent and popular until their environmental hazards were
seen to outweigh their benefits. New formulations which
retard the growth of the mildew and fungi are being used. As
noted, lead was eliminated after 1950. Most recently,
volatile organic solvents in oil paint and thinners have been
categorized as environmentally hazardous.
A major difference in
modern paints is the change in binder from the use of natural
boiled linseed oil to an alkyd oil which is generally derived
from soybean or safflower oil. Use of synthetic resins, such
as acrylics and epoxies, has become prevalent in paint
manufacture in the last 30 years or so. Acrylic resin
emulsions in latex paints, with water thinners, have also
become common.
[SIDEBAR]
Types of Historic
Paints
Historic paints were
often made with what was available, rather than adhering to
strict formulas. Recipes for successful formulas can be found
in historic documents, such as newspapers, illustrating the
combinations of ingredients which could be used to produce a
paint.
Oilbased paints: Linseed
oil, a volatile thinner such as turpentine; a hiding pigment
(usually white lead) and coloring pigments.
Enamels: natural resin
varnish was added to oil-based paint to provide a hard, more
glossy surface.
Glaze: a translucent
layer applied to protect the paint and to impart a more
uniform gloss surface. Usually made from linseed oil with
natural resin varnish added. Some glazes have small
quantities of tinting pigments such as verdigris or Prussian
blue; some had no pigments added.
Waterbased paints: Water,
pigment, and a binder, such as hide glue, other natural
glues, or gums. Usually used on interior plaster
surfaces.
Whitewash: often used on
interior plaster surfaces in utilitarian spaces and, at
times, used on interior beams; consisted of water, slaked
lime, salt, and a variety of other materials. Occasionally a
pigment (usually an ochre or other earth pigment) was added
to provide tint or color.
Distemper: used for
interior applications, were made from water, glues (one or
more different natural glues, gelatine, and gums) with
whiting as the basic white pigment to which other tinting
pigments were added.
Calcimine, or kalsomine:
often used on interior surfaces and is another common name
for distemper.
Tempera: paint prepared
with pigment, egg yolk or white and water; used almost
exclusively for decorative treatments.
Gouache: a waterbased
paint made of whiting, pigment, water, and gum arabic as the
binder; used almost exclusively for decorative
treatments.
Milkbased paint:
Casein: also called milk
paint, was made with hydrated (slaked) lime, pigment, and
milk. Most often oil was added, making a strong emulsion
paint. Various recipes call for a large variety of additives
to increase durability. Casein paints were also used for
exterior surfaces.
Pre-1875 Paints
Production and
Appearance. How were paints made prior to the widespread use
of factory-made paint after 1875? How did they look? The
answers to these questions are provided more to underscore
the differences between early paints and today's paints than
for practical purposes. Duplicating the composition and
appearance of historic paints, including the unevenness of
color, the irregularity of surface texture, the depth
provided by a glaze topcoat, and the directional lines of
application, can be extremely challenging to a contemporary
painter who is using modern materials.
The pigments used in
early paints were coarsely and unevenly ground, and they were
dispersed in the paint medium by hand; thus, there is a
subtle unevenness of color across the surface of many pre1875
paints (see Figure 4). The dry pigments had to be ground in
oil to form a paste and the paste had to be successively
thinned with more oil and turpentine before the paint was
ready for application. The thickness of the oil medium
produced the shiny surface desired in the 18th century. In
combination with the cylindrical (or round) shaped brushes
with wood handles and boar bristles, it also produced a paint
film with a surface texture of brush strokes.
Geographical Variation.
The early churches and missions built by the French in Canada
and the Spanish in the southwestern United States often had
painted decoration on whitewashed plaster walls, done with
early waterbased paints. By the mid17th century oil paint was
applied to wood trim in many New England houses, and
whitewash was applied to walls. These two types of paint, one
capable of highly decorative effects such as imitating marble
or expensive wood and the other cheap to make and relatively
easy to apply, brightened and enhanced American interiors. In
cities such as Boston, Philadelphia, New York, and later,
Washington, painters and stainers who were trained guildsmen
from England practiced their craft and instructed
apprentices. The painter's palette of colors included black
and white and grays, buffs and tans, ochre yellows and iron
oxide reds, and greens (from copper compounds) as well as
Prussian blue. That such painting was valued and that a
glossy appearance on wood was important are substantiated by
evidence of clear and tinted glazes which may be found by
microscopic examination.
Brush Marks. Early paints
did not dry out to a flat level surface. Leveling, in fact,
was a property of paint that was much sought after later, but
until well into the 19th century, oil paints and whitewashes
showed the signs of brush marks. Application therefore was a
matter of stroking the brush in the right direction for the
best appearance. The rule of thumb was to draw the brush in
its final stokes in the direction of the grain of the wood.
Raisedfield paneling, then, required that the painter first
cover the surface with paint and afterward draw the brush
carefully along the vertical areas from bottom to top and
along the top and bottom bevels of the panel
horizontally from one side
to the other.
In the 19th and early
20th centuries, for very fine finishes, several coats were
applied with each coat being rubbed down with rotten stone or
pumice after drying. A four to five coat application was
typical; however nine coats were not uncommon at the end of
the century for finishes in some of the grand mansions.
Generally, they were given a final glaze finish. Though
expensive, this type of finish would last for decades and
give a rich, smooth appearance.
Color. Color matching is
complicated by the fact that all early paints were made by
hand. Each batch of paint, made by painters using books of
paint "recipes" or using their own experience and instincts,
might well have slight variations in color--a little darker
or lighter, a little bluer and so on. The earliest known book
of paint formulations by an American painter is the 1812
guide by Hezekiah Reynolds. It gives instructions for the
relative
quantities of tinting
pigments to be added to a base, but even with proportions
held constant, the amount of mixing, or dispersion, varied
from workman to workman and resulted in color
variations.
Knowing all of the facts
about early paints can aid in microscopic paint study. For
example, finding very finely and evenly ground pigments,
equally dispersed throughout the ground or vehicle, is an
immediate clue that the paint was not made by hand but,
rather, in a factory.
By the first decades of
the 19th century more synthetic pigments were
available--chrome yellow, chrome green, and shades of red.
Discoveries of light, bright, clear colors in the plaster and
mosaic decoration of dwellings at Pompeii caught the fancy of
many Americans and came together with the technology of paint
to make for a new palette of choice, with more delicacy than
many of the somewhat greyeddown colors of the 18th century.
Of course, the blues which could be produced with Prussian
blue in the 18th and 19th centuries were originally often
strong in hue. That pigment--as were a number of others-- is
fugitive, that is, it faded fairly quickly and thus softened
in appearance. It should be remembered that high style houses
from the mid17th to late 19th centuries often had wallpaper
rather than paint on the walls of the important rooms and
hallways.
Glossy/Flat. Another
paint innovation of the early 19th century was the use of
flatter oil paints achieved by adding more turpentine to the
oil, which thus both thinned and flatted them. By the 1830s
the velvety look of flat paint was popular. Wherever
decorative plaster was present, as it
frequently was during the
height of the Federal period, distemper paints were the
coating of choice. Being both thin and readily removable with
hot water, they permitted the delicate plaster moldings and
elaborate floral or botanical elements to be protected and
tinted but not obscured by the buildup of many paint layers.
(The use of waterbased paints on ceilings continued through
the Victorian years for the same reasons.)
Unfortunately, flat
paints attract dirt, which is less likely to adhere to high
gloss surfaces, and are thus harder to wash. Victorians
tended to use high gloss clear (or tinted) finishes such as
varnish or shellac on much of their wood trim and to use flat
or oil paints on walls and ceilings.
Decorative Painting. In
interiors, paint could be used creatively and imaginatively,
most often to decorate rather than to protect. Decorative
forms included stencilling, graining and marbleizing, and
trompe l'oeil (see Figures 5, 6). Stencilling. Stencilled
designs on walls were often used in the first half of the
19th century in place of wallpaper. Old Sturbridge Village,
in Massachusetts, has paintings showing the interiors of a
(c. 18151820) farmhouse which has both stencilled
walls--imitating wallpaper--and painted floors or oiled and
painted floor cloths, imitating fine carpets. By 1850 and for
the next 60 years thereafter, stencilled and freehandpainted
decoration for walls and ceilings became a high as well as a
humble art. Owen Jones' Grammar of Ornament, published in
1859, provided the source for painted decoration from
Portland to Peoria, Savannah to San Francisco.
Graining and marbleizing.
If floors, walls, and ceilings were decorated by paint in a
variety of styles, the wood and stone trim of rooms was not
omitted. The use of faux bois, that is, painting a plain or
common wood such as pine to look like mahogany or some finer
wood, or faux marbre, painting a wood or plaster surface to
look like marble--realistically or fantastically--was common
in larger homes of the 18th century. By the early 19th
century, both stylized graining and marbleizing adorned the
simple rural or small town houses as well. Often baseboards
and stair risers were marbleized as were fireplace surrounds.
Plain slate was painted to look like fine Italian marble. In
many simple buildings, and, later, in the Victorian period,
many prominent buildings such as town halls and churches, the
wood trim was given a realistic graining to resemble quarter
sawn oak, walnut, or a host of other exotic woods.
Trompe L'oeil. Churches,
courthouses, and state capitols frequently received yet
another remarkable use of paint: trompe l'oeil decoration.
Applied by skilled artists and artisans, painted
designs--most often using distemper paints or oils--could
replicate threedimensional architectural detailing such as
ornate molded plaster moldings, medallions, panels, and
more.
Factory-Made Paints
after 1875
An enormous growth of the
paint industry began in the 1860s, stimulated by the
invention of a suitable marketing container--the paint can.
The first factory-made paints in cans consisted of more
finely ground pigments in an oil base; after purchase,
additional oil was added to the contents of the can to make
up the paint. Such paints saved the time of handgrinding
pigments, and were discussed at length by John Masury in his
numerous books. After 1875, factory-made paints were
available at a reasonable cost and, as a result, greater
numbers of people painted and decorated more of their
buildings, and more frequently. The new commercial market
created by readymixed paint became the cornerstone of our
modern paint industry (see Figure 7).
20th Century Paints
By the early decades of
the 20th century, popular taste turned away from exuberant
colors and decoration. Until the late 1920s both the Colonial
Revival and Arts and Crafts styles tended toward more subdued
colors and, in the case of Colonial Revival, a more limited
palette. The use of faux finishes, however, continued.
Residential architecture often featured stencilling, such as
painted borders above wainscoting or at ceiling and wall
edges to imitate decorative wallpaper. Institutional
buildings in both cities and small towns used wood graining
on metalclad doors, door and window frames, and staircases,
and had stencilled ceilings as well. Many high style public
buildings of the 1920s had painted ceilings which imitated
the Spanish and Italian late medieval and Renaissance
styles.
Although stenciling,
gilding, and faux finishes can be found, they did not express
the modern style of the time. On the other hand, glaze
treatments were often used in the early 20th century to
"antique" walls and trim that had been painted with neutral
colors, especially in Spanish Colonial Revival and Mission
architecture. The glazes were applied by ragging, sponging,
and other techniques which gave an interesting and uneven
surface appearance. Colored plasters were sometimes used, and
air brushing employed to give a craftsman-like appearance to
walls, trim, and ceilings. During the same period,
Williamsburg paint colors were produced and sold to people
who wanted their houses to have a "historic Georgian look."
Churches, country clubs, and many private buildings adopted
the Williamsburg style from the late 20s onward.
Often decorated with
simple molded plaster designs of the Art Deco and Art Moderne
styles, interiors of the 1930s and 1940s were frequently
accented with metal flake paints in a full range of metallic
colors, from copper to bronze (see Figure 8). And enamels,
deep but subdued hues, became popular. Paint technology had
progressed and varying degrees of gloss were also available,
including the mid-range enamels, variously called satin,
semigloss, or eggshell. In contrast to Victorian paint
treatments, this period was characterized by simplicity. To
some extent, the Bauhaus aesthetic influenced taste in the
1950s; interior paints were frequently chosen from a palette
limited to a few "earth" colors and a "nearly neutral"
palette of off-whites and pale greys.
While the trend in colors
and decorative treatments was defined by its simplicity,
paint chemists were developing paints of increasing
complexity. Experimentation had started early in the 20th
century and accelerated greatly after World War II. Of
greatest significance was the manufacture of the latex paints
for consumer use. Synthetic resin emulsions carried in water
offered advantages over the traditional oil paints, and even
over the oil/alkyd paints: they did not yellow; they
permitted water cleanup until dried; and they emitted no
toxic or hazardous fumes from solvent evaporation.
Paint Investigation
Understanding each
project's historic preservation goal and knowing what level
of information needs to be collected to achieve that goal is
an important responsibility of the purchaser of the service.
Before someone is hired, the owner or manager needs to decide
if a thorough investigation of painted surfaces is actually
needed, and how to use the results when one is
done.
Specialists with both
training and field experience conduct paint investigations.
These experts use sophisticated instruments and procedures
such as field sampling, cross-section analysis, and
fluorescent and chemical staining to learn about the
components and behaviors of historic paints (see Figure 9).
In addition, they utilize written documentation, verbal
research, and visual information about past painting in the
building in conjunction with findings in the field (Figure
10).
Paint investigation can
make several contributions to a project. A complete analysis
of the paint layers on surfaces within a structure can tell a
great deal about the sequence of alterations that have
occurred within a building, as well as potentially providing
ranges of dates for some of these changes. By establishing a
full sequence of paint layers (termed a chromochronology ),
together with other research, alterations of various building
spaces and features can be associated with specific paint
layers. It is by establishing this association that the
correct layer is identified; when the correct layer has been
identified, the color may be matched.
In addition to its
archeological value, paint analysis can determine the types
and colors of paint on a given surface (identification of
thin glazes, decorative paint schemes, binders and pigments).
Beyond color identification, then, paint analysis is also
recommended to diagnose causes of paint failure. Knowing a
paint binder can often explain causes as well as guide
appropriate preservation or conservation treatments.
Owners and managers
should identify all of these needs before deciding on the
extent of analysis. For example, a complete paint
investigation is usually recommended as part of an historic
structure report. For buildings with little documentation,
additions and alterations can often be identified, and
possibly dated, through analysis. Often the use of such
seemingly expensive techniques can save money in the long run
when determining the history of building change.
It is possible to do some
analysis on site; this is a much simpler process that can be
undertaken for less cost than the complex laboratory
procedures described above. However, the usefulness of onsite
analysis is limited and the results will not be as precise as
results from samples that are analyzed in a laboratory with a
good microscope. Any shortcut approaches to paint analysis
that do not follow scientific procedures are generally not
worth the expense. In summary, if preservation and
restoration treatments are being undertaken, a complete
investigation is recommended; for a rehabilitation project,
onsite analysis and color matching may provide an adequate
palette.
Choosing a Treatment
Most projects involve
repainting. It is the historic appearance of the interior and
the visual impression that will be created by new paint
treatments that must be considered before choosing a
particular course of action. The type and colors of paint
obviously depend on the type of building and the use and
interpretation of its interior spaces (see Figure 11). A
consistent approach is best.
Preservation. When the
treatment goal is preservation, a building's existing
historic features and finishes are maintained and repaired,
saving as much of the historic paint as possible. Sometimes,
cleaning and washing of painted surfaces is all that is
needed. Or a coating may be applied to protect important
examples of history or art (see Figure 12). If repainting
is
required, the new paint
is matched to existing paint colors using the safer, modern
formulations. Recreating earlier surface colors and
treatments is not an objective.
Rehabilitation. In a
typical rehabilitation, more latitude exists in choosing both
the kind of new paint as well as color because the goal is
the efficient reuse of interior spaces. Decisions about new
paint often weigh factors such as economy and durability--use
of a high quality standard paint from a local or national
company and application by a qualified contractor. Color
choices may be based on paint research reports prepared for
interior rooms of comparable date and style. More often,
though, current color values and taste are taken into
account. Again, the safer paint formulations are used (see
Figure 13).
Interiors of
institutional buildings, such as university buildings, city
halls, libraries, and churches often contain rich decorative
detailing (Figure 14). During rehabilitation, careful choices
should be made to retain or restore selected portions of the
decorative work as well as match some of the earlier colors
to evoke the historic sense of time and place. At the least,
it is important to use periodtypical paint color and paint
placement.
Restoration. In a
restoration project, the goal is to depict the property as it
appeared during its period of greatest significance. This may
or may not be the time of its original construction. For
example, if a building dated from 1900 but historians deemed
its significance to be the 1920s, the appropriate paint color
match would be the 1920s layer, not the original 1900
layer.
Based on historical
research, onsite collection of paint samples, and laboratory
analysis, surface colors and treatments can be recreated to
reflect the property at a particular period of time. It
should be noted that scholarly findings may yield a color
scheme that is not suited to the taste of the contemporary
owner, but is nonetheless historically accurate. In
restoration, personal taste in color is not at issue; the
evidence should be strictly followed.
In the restoration
process, colors are custommatched by professionals to give an
accurate representation. If an artist or artisan can be
found, the historically replicated paint may be applied using
techniques appropriate to the period of the restoration (see
Figure 15). Although custom paint manufacture is seldom
undertaken, color and glazing are capable of being
customized. In some projects, paint may be custommade using
linseed oil and, if building code variances allow it, white
lead. For example, the repainting of a number of rooms at
Mount Vernon demonstrates that it is possible to replicate
historic paints and applications in all aspects; however, as
noted, replication of historic paint formulation is not
practical for the majority of projects.
Identifying
Deteriorated and Damaged Paint Surfaces
Because painted surfaces
are subject to abrasion, soiling, water damage, sunlight, and
application of incompatible paints they generally need to be
repainted or at least reglazed appropriately from time to
time.
Abrasion. From the
baseboards up to a level of about six feet off the floor,
wood trim is constantly subjected to wear from being touched
and inadvertently kicked, and from having furniture pushed
against it (see Figure 16). Chair rails were in fact intended
to take the wear of having chairs pushed back against them
instead of against the more delicate plaster wall or
expensive wallpaper. Doors in particular, sometimes
beautifully grained, receive extensive handling. Baseboards
get scraped by various cleaning devices, and the lower rails
of windows, as well as window seats, take abuse. The paint in
all of these areas tends to become abraded. Two things are
important to bear in mind about areas of abraded paint.
Samples taken to determine original paint colors and layer
sequences will not be accurate except at undamaged edges.
Also, dirt and oil or grease need to be removed before
applying any new paint because new paint will not adhere to
dirty, greasy surfaces.
Dirt. Soiling is another
problem of interior paint (see Figure 17). Fireplaces smoked;
early coalfired furnaces put out oily black soot; gas lights
and candles left dark smudges. Sometimes the dirt got
deposited on plaster walls or ceilings in a way that makes
the pattern of the lath behind the plaster quite clear.
Another source of dirt was polluted outside air, from
factories or other industries, infiltrating houses and other
nearby buildings. Until smokestacks became very high, most
air pollution was caused by nearby sources.
In paint investigation,
dirt on the surface of paint layers; as seen under the
microscope, can be very useful in suggesting the length of
time a given paint layer remained exposed, and in
distinguishing a finish layer from a prime or undercoat
layer. This kind of soiling can happen on any painted surface
in a room, but may be slightly heavier in the recesses of
moldings and on upwardfacing horizontal edges. Using dirt as
a sole measure, however, may be misleading if the surfaces
have been cleaned. The fracture or bonding between paint
layers is often used by professionals as a better means of
indicating time differences between layers as well as
indicating those layers that are part of a single decoration
or painting.
Water. Water, the usual
source of deterioration for many kinds of material, is also a
prime cause of interior paint failure (see Figure 18). As a
liquid, it can come from roof leaks, from faulty plumbing or
steam heating systems, or from firesuppression systems that
have misfired. As a vapor, it may come from such human
activities as breathing, showering, or cooking. Plaster walls
sealed with unpigmented hideglue are notably susceptible to
water damage because it forms a watersoluble layer between
the plaster and the paint. This can cause the paint to lose
adhesion when even small amounts of moisture come into
contact with the watersoluble sealer.
Age/Sunlight. Finally, in
historic interiors, especially where there is heavy paint
buildup, paint can weaken and fail due to chemical or
mechanical reasons. For example, the older linseed oil is,
the more brittle it is (see Figure 19). It also darkens when
it is covered and gets no ultraviolet exposure. In rooms
where there is more sunlight on one area than on others, the
oil or even oil/alkyd paint will get discernibly darker in
the less exposed areas in as short a time as six months.
Painted over, the oil medium in older paints gets quite
yellowbrown, thus changing the color of the paint. Prussian
blue is one of the tinting pigments that is particularly
vulnerable to fading.
Incompatible Paints.
Understanding some basic differences in the strength of
various paints helps to explain certain paint problems.
Paints that dry to a stronger film are incompatible with
those which are weaker. Acrylic latex paints are stronger
than oil/alkyd paints. Oil or oil/alkyd paint is stronger
than waterbased paint such as calcimine. When a stronger
paint is applied over a weaker paint, it will tend to pull
off any weaker paint which may have begun to lose its bond
with its substrate. Thus, on many ceilings of older buildings
where oil/alkyd paints have been applied over old calcimine,
large strips of paint may be peeling.
Oil or varnish glazes
over older paints become brittle with age, and can make
removal of later paints rather easy. Sometimes it is possible
to take advantage of this characteristic to reveal an earlier
decorative treatment such as graining or marbleizing. Getting
under the edge of the glaze with a scalpel blade can make the
removal of later paints relatively simple, and relatively
harmless to the fancier paint treatment. Sometimes, paints
separate from each other simply due to poor surface
preparation in the past or the hardening of the earlier
surface paint. Use of alkaline paint strippers can cause
paint to lose adhesion. When insufficiently neutralized, they
leave salts in wood which cause oil or oil/alkyd paints to
fail to adhere to the surface. If dirt or oily residues are
not cleaned from the surfaces to be painted, new paint will
not remain well adhered.
Surface
Preparation
First, it is important to
note that the earlier, linseed oil-based paints were
penetrating type paints, forming a bond by absorption into
the substrate. Often these thin oil coatings were slightly
tinted with an ironoxide pigment so coverage could be seen;
the next coating applied would adhere to this first oil
layer. Modern paints, on the other hand, are primarily
bonding paints with little ability to penetrate a substrate.
For this reason, surface preparation is extremely important
for today's paints.
Before preparing the
interior for repainting, all moisture penetration from
failing roofs or gutters or from faulty plumbing or interior
heating elements should be identified and corrected. A paint
job is only as good as the preparation that goes before it.
The surface to be painted, old or new, wood, plaster,
masonry, or metal must be made sound and capable of taking
the paint to be applied.
Scraping and Sanding. The
first step in preparing interior wood and plaster surfaces
which are coherent and sound is to remove any loose paint
(see Paint Hazards sidebar). Careful hand scraping is always
advisable for historic surfaces. Use of mechanical sanders
usually leaves traces of the sander's edges, visible through
the new paint film. Hand sanding is also necessary to feather
the edges of the firmly adhering layers down to the bare
areas so that shadow lines are avoided. Preparing previously
painted interior masonry for new paint is basically similar
to preparing plaster. Metals elements, such as radiators,
valences, or firebacks are somewhat different (see Figure
20). In order to get a sound paint job on metal items, the
work is primarily that of sanding to remove any rust before
repainting. If the existing paint is well adhered over the
entire metal surface, then it may be necessary only to sand
lightly to roughen the existing paint, thus providing some
"tooth" for the primer and new paint layer. On wood, garnet
sanding papers work well. Aluminum oxide and silicon carbide
sandpapers are effective on other surfaces as well as wood;
emery papers should be
used on metals.
Paint Removal. When
should surfaces be completely stripped? Obviously, new paint
is wasted when applied on old paint which is loose, that is,
extensively damaged and deteriorated. Sometimes paint on an
architectural feature needs to be removed if it obscures
delicate detailing (see Figure 21). For the most part,
however, if the surface is intact--and the presence of lead
paint has been shown to present no health dangers to building
occupants--the existing paint can be overpainted.
Welladhered, intact paint
layers (in at least one area of each room) should be covered
with a sturdy protective tape, then painted over with the new
paint and left in place to inform future research. The next
owner may be interested in the building's past history, and
methods of gleaning information from old paints grow more
sophisticated all the time.
Heat/Scraping. Propane
torches should never be used because they can damage historic
wood features. Also, charred areas of wood will not hold the
new paint. Use of a heat gun or heat plate may be relatively
fast, but has both health and safety drawbacks. Heat oxidizes
lead paint, causing poisonous fumes. And old walls may
contain fine debris which acts like tinder and smolders when
heated, bursting into flame hours after the stripping. (Heat
methods are best limited to those interior elements that can
be safely removed from the building for stripping and
reinstalled). Finally, scraping to remove heatloosened paint
may gouge and scar the wood or plaster substrate if not done
carefully. Rotary wire brushes cut into wood and should be
avoided altogether.
Chemical stripping.
Removing paint from wood and plaster features can be done
with either caustic strippers (potassium or sodium hydroxide)
or solvent strippers (organic compounds such as methylene
chloride, methanol, or toluol). Caustic strippers are fairly
fast acting, but can weaken wood fibers if left on too long,
causing them to raise and separate. They also leave alkaline
residues which must be neutralized by an acidic wash (usually
white vinegar which contains 4% acetic acid). It is difficult
to make the neutralizing 100% effective and, when it is not,
chemical reactions between the alkaline residues and the new
paint may cause the paint to lose adhesion.
Methylene chloride and
other organic compounds are as effective as caustic
strippers, but their fumes may be both flammable and toxic.
While they may leave wood and plaster surfaces free from
harmful residue, the newly cleaned surface must be washed
down with mineral spirits or denatured alcohol before priming
in order to remove additives, such as wax, that were put in
the stripper to retard its drying. All hazard warnings on the
labels of chemical strippers should be heeded.
Detergent or vinegar and
water. Waterbased paints can usually be scrubbed off with hot
water with a detergent added. Calcimine and whitewash are
difficult to remove; because of the lime or whiting content
(calcium carbonate), however, they can be broken down with
acids. While strong acids may work quickly, they are very
dangerous. Acetic acid in its most common form, vinegar, (4%
acetic acid) is often used instead. In areas where any
calcimine remains and is evident as chalk, the area can be
coated with white shellac, which provides a stable surface
for the new paint.
Air pressure. Air
pressure of 200500 psi is effective for flat surfaces if
there is a weak substrate surface bond. A flat nozzle is
inserted between the paint layer and substrate, and the air
pressure simply lifts the loose paint up for easy removal.
When used carefully, this method is fast and causes little
damage.
Patching and Repair. Once
the substrate and its surface are sound and clean, free from
crumbling, loose material or dust, the next step is to
undercut and fill any cracks in plaster surfaces. Plaster
which has lost its key and is sagging should be reattached or
replaced. Friable plaster and punky wood need to be
consolidated. Wood surfaces should be made as smooth as they
were historically so that the paint film will cover a
relatively uniform surface. Rotted wood must be removed and
new wood carefully spliced in. Finally, gypsum plaster
finishes can be painted as soon as the water has evaporated;
a lime putty coat or traditional finish plaster can be primed
almost immediately after drying as well, using
alkaliresistant primers such as acrylic latex.
Priming. The importance
of a primer can hardly be overstated. It is the intermediary
material between the immediate substrate, which may be an old
paint layer or may be bare wood, plaster, or metal (rarely
stone, as around a fireplace opening), and the fresh paint
itself. The primer must be capable of being absorbed to some
extent by the material underneath while being compatible and
cohesive with the paint to be applied on top. Most paint
manufacturers will provide explicit instructions about which
primers are most compatible with their paints. Those
instructions should be followed.
The question of a primer
for latex paint continues to be debated. Traditionalists
recommend that the primer between an old oil paint and a new
latex paint be an oil primer, but the improvements to latex
paint in recent years have led many experts to the conclusion
that today's top grade latex primers are best for latex
finish paints. If a latex primer is selected, the label on
the can should specify clearly that it is one which can bond
to an older oil or oil/alkyd paint.
The most important
general rule to remember is that softer or weaker paints
should always go over harder and stronger paints. For
instance, because latex is stronger than oil, an oil or
oil/alkyd paint can go over a well adhered latex, but the
reverse will run the risk of failure. Using primer and finish
paints by a single company is a good way to guarantee
compatibility.
Choosing
Modern Paint Types/Finish Coats
Most frequently today,
the project goal is preservation or rehabilitation. Because
of the impracticality of replicating historic paints,
restoration is least often undertaken. Given current laws
restricting the use of toxic ingredients, such as lead,
solvents, and thinners, contemporary substitute paints using
safer ingredients need to be used. Many paint companies make
latex paints in colors that are close to historic colors as
well as appropriate gloss levels, but contain no white lead
and no hazardous volatile organic compounds.
Work on historic
properties generally requires the services of a qualified
paint contractor who has had at least five years of
experience and who can list comparable jobs that a potential
client can see. Then, too, getting a sample or a mockup of
any special work may be advisable before the job starts.
While less experienced workers may be acceptable for
preparing and priming, it is wise to have the most
experienced painters on the finish work.
Oilbased/alkyd paints.
Today's version of oil paint has a binder that usually
contains some linseed oil (read the paintcan label), but also
has one of the improved synthesized oils, frequently
soybased, known as alkyds. They dry hard, have flexibility,
and discolor far less than linseed oil. They can also be
manufactured to dry with a high sheen, and can take enough
tinting pigment to create even the very deep Victorian period
colors. However, they all contain volatile organic compounds,
and thus are forbidden by law in some parts of the United
States. They are also less simple and more dangerous to use,
as cleaning up involves mineral spirits.
Acrylic waterborne paints
(latex). Latex paints are synthetic resins carried in water.
Before the paint dries or crosslinks, it can be cleaned up
with water. Early in the history of latex paints, some
contained styrene/butadiene resins. Now nearly all topgrade
latex paints contain acrylic resins, which are superior.
Also, until fairly recently, the latex paints, while offering
great strength, quick drying, and water cleanup, had some
disadvantages for jobs which needed to have an historic look.
Today, there are latex product lines with better gloss
characteristics and more historic colors from which to
choose. In addition, latex paints often have excellent color
retention with very little fading. Still, it is always a good
idea to buy a quart and "test paint" the color chosen for the
job on site before making a total commitment.
Calcimine/whitewash.
Modern waterbased paints such as calcimine can be purchased
today and have much the same appearance as the early ones.
The same is true of modern whitewash, although today's
whitewashes do not leave the same ropy surface texture as the
early ones.
Glazes. Glazes were often
part of historic paint treatments. Traditionally oil and
turpentine, sometimes with a scant amount of pigment, today's
glazes can be formulated with a water base and are relatively
simple to apply by brush. An experienced decorative painter
should be consulted before deciding whether to use a glaze
coat rather than a high-gloss enamel. The glaze is capable of
providing protection as well as a more accurate historic
appearance that includes a greater depth to the
finish.
Epoxies/Urethane. These
were not available until relatively recently and thus are not
appropriate for replication of traditional finishes.
Applying Interior
Paints
Because flat wall
surfaces generally dominate an interior painting job, some
flexibility in applicators is suggested below:
Brushes. Natural bristle
brushes now have competition from synthetic brushes made of
nylon or polyester which work well for applying either
oil/alkyd or latex paints. Being harder than natural
bristles, they tend to last longer. Since brushes come in a
wide and very specific variety of types suited to different
types of work, it is important to have a painter who will use
the appropriate brush for the paint selected and for each
portion of the job. One strong advantage of brushing paint on
is that the paint is forced onto the surface and into all of
its imperfections. Thus a good brushedon paint job may last
longer if the substrate is sound and the primer and finish
coats are compatible and of top quality.
Rollers. There is no harm
in using a roller, or even an airless sprayer, to apply a
prime coat to a large flat area. Since all contemporary
commercial paints dry with a smooth surface anyway, use of a
roller or sprayer is acceptable for priming, and even for a
first finish coat. However, to get paint well pushed into
articulated surfaces and to add some texture to larger flat
surfaces, a brush is best.
Types of Modern Paint
Oilbased/alkyd:
Nonvolatile oils and resins, with thinners. (Alkyds are
synthetic, gelatinous resins compounded from acids and
alcohol.) Accept almost any type of coloring/hiding pigments.
For use on interior wood and metal.
Acrylic waterborne paints
(latex): Suspension of acrylic or polyvinyl resins in water,
with other resins, plus hiding and coloring pigments and
extenders. Dries by evaporation. Commercially produced
acrylic or latex enamels are also available in a complete
range of gloss levels which are produced with the addition of
various acrylic polymers. Use on interior plaster
especially.
Enamels: Modern alkyd
paints are adjusted with the addition of synthetic varnishes
to produce a complete range of gloss levels.
Metal finishes: Paints
marketed for use on metals, can either be alkyd, latex, or
epoxy based, or combinations. The primers used for metals are
formulated with rustinhibiting ingredients.
Special finishes:
finishes such as urethane and epoxy-based paints, marketed
for very high gloss surface treatments.
Finally, decorative paint
work in an historic interior-- whether simple or
highstyle--is well worth preserving or restoring, and when
such fancy work is being undertaken, traditional tools should
always be used (see Figure 22). To simplify by using shortcut
methods or rejecting painted decoration is indeed to dismiss
or skew history as well as to lose the enjoyment of a true
historic finish.
Summary
First, it is most
important to understand the range of approaches and
treatments and to make choices with as much knowledge of the
original and subsequent historic paints as possible, using
the Secretary of the Interior's Standards for Historic
Preservation Projects as a framework.
A paint's patina of age
expresses decades or centuries of endurance in the face of
changing climate and conditions. Documenting the sequence of
interior paint layers and protecting this information for
future investigation should be an integral part of any
historic preservation project.
Except for the rare,
scholarly restorations of historic interiors, most repainting
jobs done today will employ modern paint formulations. Modern
paints can recreate the appearance of historic colors, gloss
and texture in varying degrees, but eliminate earlier toxic
components such as white lead and volatile organic
compounds.
CAUTION: Before Painting Know Paint Hazards and
Take Action
Before undertaking any
project involving paint removal, applicable State and Federal
laws on lead paint abatement and disposal must be taken into
account and carefully followed. State and Federal
requirements may affect options available to owners on both
paint removal and repainting. These laws, as well as any
requirements prohibiting volatile organic compounds (VOCs),
should be requested from the State Historic Preservation
Officer in each State.
Below is a summary of the
health hazards that owners, managers, and workers need to be
aware of before removing paint and repainting:
Lead and other heavy
metal compounds. In virtually all paints made before 1950,
the white or "hiding" pigment was a lead compound, or more
rarely, zinc oxide. Work to remove lead paint such as
scraping and dry sanding releases the lead--a highly damaging
heavy metal--in dust. Lead dust then enters the human system
through pores of the skin and through the lungs. The use of
heat for stripping also creates toxic lead fumes which can be
inhaled.
To mitigate the hazards
of lead paint ingestion, inhalation, or contact, it is
extremely important to prevent the dust from circulating by
masking room openings and removing all curtains, carpeting,
and upholstered furniture. Drop cloths and masking containing
lead dust should be carefully enclosed in tight plastic bags
before removal. Workers and others in the room should wear
High Efficiency Particulate Air (HEPA) filters for lead dust
(fume filters if heat stripping is being used), change
clothing just outside the room leaving the work clothes
inside, and avoid any contact between bare skin (hands) and
the paint being removed. Workers should also not eat, drink,
or smoke where lead dust is present. Finally, anyone involved
in lead paint removal should undergo periodic blood testing.
After work, ordinary vacuuming is not enough to remove lead
dust; special HEPA vacuums are essential. The surfaces of the
room must also be given a final wash with a solution of
trisodium phosphate and water, changing the washing solution
often and rinsing well.
In addition to lead,
early oil paints also had cobalt or other heavy metal
compounds in them to accelerate drying. A small amount of
mercury is also included in some latex paints to help prevent
mildew and mold formation.
Volatile organic
compounds (VOCs). Organic paint strippers, such as methylene
chloride, and oil/alkyd paints have VOCs as their solvent
base. Inhaling these fumes can lead to respiratory and other
illnesses, and to cancer. Especially in closed spaces (but in
the outdoor environment as well) these compounds pollute the
air and can damage health.
Additional Reading
Clark, Victor S. History
of Manufacturers in the United States Vols. IIII. New York:
McGrawHill, 1929.
Gettens, Rutherford J.
and George L. Stout. Painting Materials: A Short
Encyclopedia. New York: Dover Publications, 1966.
MacDonald, Marylee.
Preservation Briefs 21: Repairing Historic Flat
Plaster--Walls and Ceilings. Washington, D.C.: National Park
Service, U.S. Department of the Interior, 1989.
Masury, John W. A Popular
Treatise on the Art of HousePainting: Plain and Decorative.
New York: D. Appleton & Co.,. 1868.
Weeks, Kay D. and David
W. Look, AIA. Preservation Briefs 10: Exterior Paint Problems
on Historic Woodwork. Washington, D.C.: National Park
Service, U.S. Department of the Interior, 1982.
Winkler, Gail Caskey and
Roger W. Moss. Victorian Interior Decoration: American
Interiors 18301900. New York: Henry Holt and Company,
1986.
Organizations
National Paint and
Coatings Association
1500 Rhode Island Ave. N.W.
Washington, D.C. 20005
Painting and
Decorating Contractors of America
3913 Old Lee Highway, Suite 33B
Fairfax, VA 22030
Federation of
Societies for Coatings Technology
492 Norristown Rd.
Blue Bell, PA 19422-2350
Acknowledgements
Thanks go to the
technical experts in the field who reviewed the draft
manuscript and made substantive contributions: Andrea M.
Gilmore (Director, Architectural Services, Society for the
Preservation of New England Antiquities), Andy Ladygo
(Jefferson's Poplar Forest), and Matthew J. Mosca, Historic
Paint Research. Insightful comments were also offered by E.
Blaine Cliver, Chief, Preservation Assistance Division. In
addition, Technical Preservation Services Branch staff
members (H. Ward Jandl, Chief) and the NPS Regions provided
valuable suggestions on both content and organization.
Washington, D.C. June,
1992
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