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Paint Research for Historic Homes

If you have an antique home and are aiming for authenticity, historic paint research can be a great investment. It can reveal when different woodwork was installed, and, in some cases, where pieces uncovered during restoration came from. It can show where architectural features, such as corner cupboards, once stood and what their dimensions were. It can disclose when different colors and treatments, like graining, were applied and how long they remained visible. Combined with documentary research, it can tell something about the social history of a house.

"I am continuously surprised by what I find," says Matthew Mosca, an expert in paint research and replication. "There were two parallel courses in the color choices people made. Some people paid attention to period fashion. Others were very imaginative. Cost was a factor, because some pigments, like verdigris, were so expensive. But people historically used paint, sometimes in striking ways, to express themselves and enliven the environment."

Conservator Andrea M. Gilmore’s essay, "Analyzing Paint Samples" in Paint in America, notes, "…on-site investigation of architectural paints begins with a thorough examination of the surfaces to be studied. Differences in the profile of molded woodwork and clearly delineated plaster cracks may be indicative of building fabric alterations; irregularities in a plaster wall surface revealed with raking light can sometimes identify the location of decorative painting, and variations in the character of the painted surface—such as circular sanding marks or lines marking areas of reduced paint buildup—identify areas where paints may have been removed. In addition… knowledge of period painting practices also suggests areas that should be sampled. During the eighteenth century paint was used to simulate chair rails and baseboards on plaster and wood-paneled walls; in the early nineteenth century over-mantel painting was common."

The simplest type of paint research is to scrape down to reveal paint layers and paint analysts like Gilmore start their research with this on-site investigation. "To know what an original paint treatment looked like, you have to expose as much of it as you can, as carefully as you can," says Will Cady Perkins, a paint restoration specialist based in Ipswich, Massachusetts. "This is especially true for graining and decorative wall painting. It is also important if you want to re-create not just the color but also the texture of the early finish." Paint researchers proceed cautiously, because toxic white lead was used in early house paints and because they don’t want to destroy evidence of decorative paint treatments, such as grain painting or stenciling on walls and ceilings. Starting from a small incision, they sand a small area, creating a broad, shallow crater with sloping sides to reveal wide swaths of earlier layers. Then, they examine the crater through a binocular field microscope (with an internal light if possible) at 5x-to-20x magnification.

Brian Powell, Gilmore’s colleague at Building Conservation Associates, in Dedham, Massachusetts, says, "Scraping is a good starting point, but it’s not enough for precise reconstruction." Why? From the 17th century on, most paint used on woodwork used linseed oil, which, darkens and yellows with age when not exposed to light. Early paint that looks tan, greenish-gray, or muddy green may originally have been lead white, gray, or a bright Prussian blue (the first synthetic pigment, discovered in Europe in 1704 and wildly popular in 18th-century America).

The best way to "see" the authentic historic color is through more sophisticated laboratory analysis. For this, historic paint analysts cut small paint samples from woodwork, reaching down to the wood substrate. At the lab, samples are studied in cross-section under magnification and different lights. Using fiber-optic halogen lamps and binocular microscopes with magnification up to 80x, polarizing and ultraviolet light microscopes with magnifications up to 500x, fluorescent staining, and micro-chemical analysis, they discern paint sequence and chronology, and identify pigments and binders. Under magnification, a dirt layer next to the wood indicates it was originally unpainted— a less common treatment than early-20th-century historians believed. Dirt, primers, varnishes, shellacs, and other resinous finishes, undetected by the naked eye, can be identified under ultraviolet light, because each fluoresces a different color.

Finishes on plaster walls are more difficult to decode than those on woodwork. Since wallpaper wasn’t commonly affordable or accessible in America until after the Revolution, the walls in the average house often had a tinted, water-soluble distemper paint (known even in its own era for flaking off) or a whitewash made with lime. Also used extensively on interior woodwork, whitewash was popular because it could be cleaned and over-painted easily, and because lime was thought to repel insects. But distempers and whitewash are such fugitive finishes that little evidence of them survives. The same is true for painted flooring, popular after the American Revolution.

Identifying pigments and binders in the lab can help date a finish, which is important if the goal is to restore a room to a particular time period. Milk, or lime casein, paints, for instance, were known in antiquity, but disappeared for centuries and were used in America only after 1800. Mineral pigments—iron oxide, red ocher, and red lead, white lead and yellow ocher—have been used since time immemorial. Pigments for other colors changed with technology. For example, synthetic yellow pigments included patent yellow introduced in 1781, Naples yellow in 1800, and chrome yellow, which supplanted both, in 1820. This information and the sequential layering of pigments can also explain what colors belong together in a room. Suppose you found that the first color on the woodwork was a circa 1730 iron oxide red, and the first color on the plaster was a blue, revealed in lab analysis to be artificial ultramarine, not used until about 1850. Without this analysis, you could "re-create" a color scheme that never existed historically.

When choosing a paint treatment, "The easiest thing is to go for the earliest period," says Powell. "Decoding later treatments can be more challenging. But, if the room’s architectural details, or the furnishings and decoration the homeowner prefers, reflect a later period, the first treatment may not be the one to highlight." ©2009 Gladys Montgomery