Traditional Masonry Archives

Lime Wash Coatings

In Mark Twain’s 1875 story “The Adventures of Tom Sawyer,” the title character is told to whitewash his Aunt Polly’s fence, a project that, like all other chores, he detests. To avoid doing the work, young Sawyer persuades neighborhood kids that painting is a form of amusement. So thoroughly does he convince them that he ultimately collects an apple, a kite, marbles, and other items for the privilege of allowing them to whitewash his aunt’s fence.

Perhaps it is fitting that Tom Sawyer’s famous whitewash scene was published in the last quarter of the 19th century. In that period massive changes were occurring in the masonry and coatings industries. Due to the advent of portland cement, bricks and mortar became tougher. The traditional protective coating for masonry, lime wash (a variant of which is whitewash) fell out of use.

Today, masonry experts involved in restoration of older brick, stucco, and stone buildings are relearning the skills and recipes necessary to apply lime wash coatings to preserve architectural and physical integrity. These experts are also beginning to notice renewed interest in the use of lime wash as a decorative coating.

The oldest coating
Many experts regard lime wash as the grandfather of all coatings. Applied by ancient Romans and Egyptians and possibly before those eras, lime wash is relatively simple to make with materials readily available in almost every corner of the world.

The process begins with lime, a substance created by burning limestone or chalk (forms of calcium carbonate) at kiln temperatures. The heat drives off carbon dioxide and moisture, leaving behind calcium oxide, also known as quicklime. Without delving too deep into manufacturing processes — some of which are guarded secrets — water is added to quicklime in a process called slaking. The resultant lime putty may be covered with water and stored in airtight containers for long periods of time. Lime putty is transformed to lime wash by the simple addition of pigment and more water. Conversely, lime putty may be made into lime mortar by adding sand.

Become sensitized
Traditionally, lime wash was used on adobe in the southwestern United States and on stucco, brick, and wood in other parts of the country, according to Sarah Jackson, an architectural conservator at the National Center for Preservation Technology and Training, part of the National Park Service.

Jackson is in charge of testing for the organization’s Study on the Durability of Traditional and Modified Lime Wash Recipes. She is currently advising the Cane River Creole National Historical Park on the application of lime wash to several historic wood or brick structures. Results of this study can be obtained by contacting Jackson or through the NCPTT Web site.

Her advice to masons not completely familiar with lime wash is to identify exactly what material they are working with before proceeding. The most surefire way is to send samples out to be tested. But such testing is not always possible.

Sarah Jackson demonstrates lime wash application at American Cemetery in Natchitoches, La.

Michael Kahn, who supplies lime washes through Sydney Harbour Paint Co., suggests using visual and tactile methods for initial identification.

“It is oftentimes identifiable by look,” Kahn says. “It will have a distinct patina and mottled look on the outside of the building. If you rub your hand over the top of the surface you’ll feel a powdery substance, which is the lime itself.”

The chalkiness is caused by sloughing as the coating ages, Kahn explains. Traditionally, lime washes were recoated every year or so, but on some structures the coating has all but disappeared over time.

“If you’re looking at a lime wash surface now, there is a good likelihood that it is well worn,” Jackson says. “You may expect to find lime wash that’s worn in a few places, but you’re more likely to find it’s been worn away except in a few places.”

Built to breathe
Restoration experts and artists working on lime wash projects should avoid the urge to substitute modern materials, says Kahn. Although it may be possible to use modern-day coatings to match the patina and mottled look of lime wash, over time the adjacent coatings will age differently.

“You might be able to recreate a surface using faux effects, but over a longer period of time you’ll lose it,” Kahn says. “Lime wash changes as it ages in a way modern paint does not. It’s actually very distinctive in the way it ages — just look at some of the beautiful buildings in Tuscany and places like that.”

In addition, modern coatings may trap moisture inside some traditional buildings’ thicker masonry walls. While high-tech buildings are designed to prevent vapor and moisture transfer, some older buildings were built to breathe.

“Modern paints are more like cellophane,” Kahn says. “They wrap up the entire building and hold in moisture.”

Homemade or store-bought?
Michael Davidson, owner of Mississippi Stone Guild, uses store-bought lime washes or mixes his own, depending upon the application. Davidson received his masonry training in Scotland and has worked all over the world.

“It’s hard to be commercial when you make your own lime wash,” Davidson says. “Each batch changes a little.”

To some building owners, subtle color differences are part of the beauty of lime wash, but others do not appreciate such differences.

“Unless you buy a commercially available wash, each batch is going to be a slightly different shade than the last one,” Davidson says. “In addition, it’s hard to mix up a batch in advance, not knowing what substrate it’s going to be used on.”

If you’re planning on lime washing, Jackson recommends consulting books or articles first to get a feel for the types of additives that may be used with lime wash. Then she recommends testing a variety of recipes to see which works best in your environment. She agrees with Davidson that for a single project, the best option may be to procure a commercially available lime wash, especially for those not yet experienced in creating the coating. But both experts have made their own lime washes to help keep costs down: Davidson for a public edifice in Eupora, Miss., and Jackson for the Cane River Creole National Historical Park.

“We also wanted to identify a recipe that the Park’s staff could use for current projects and subsequent applications,” Jackson says.

Crumbling piers
Jackson and Davidson mixed their own lime wash when they collaborated as a part of an International Preservation Trades Workshop, held in October 2006 in New Orleans to help save a historic home from the effects of Hurricane Katrina.

The house, built in the early 19th century and situated on Flood Street in the Ninth Ward, was in imminent danger of toppling. Due to the fact that much of the city is at or below sea level, the structure and others nearby were built on pilings, also called piers. This home stood on approximately two dozen brick and mortar pilings that had become saturated when flooding deposited approximately 10 feet of oily water into the streets. Close inspection revealed that in many places, the piers contained little or no mortar left to support the weight of the house. In fact, some of the old orange bricks that had previously been repaired with portland cement had lost their faces.

With extremely limited funds, Jackson and Davidson enlisted the help of 15 high school students. The first task at hand was to stabilize the piers with lime grout and mortar.

“The kids picked up the skills fairly easily, but bear in mind that in this situation we were not using the term restoration, but emergency stabilization due to the extent of the damage,” Davidson says. “We were only there for a short time and were trying to do so much. But they really were helpful. I had them cutting joints, tuck-pointing, patching spalls and that sort of thing.”

After allowing the mortar to dry, the high school kids received a demonstration in applying lime wash and were set to work. Brushes in hand, the young adults eagerly coated the pilings so that the house, decorative wrap-around porch and turn-of-the-century columns achieved a uniform look.

When asked how he motivated a group of 14- to 16-year-old kids, Davidson’s reply seemed in stark contrast to the subtle approach Tom Sawyer used to lure his friends into picking up whitewash brushes.

“On one hand you have people wanting to bulldoze the entire district due to widespread damage,” says Davidson. “On the other hand we had to convince these kids to preserve their own neighborhoods. We can stabilize these houses. The amount of work can be daunting, but certainly a lot of these homes can be saved.”

Born again
Obviously, the best choice in restoring and preserving historic buildings is to stick with original materials. Although the use of lime wash diminished greatly during the 20th century, the beauty, protection, and near-instant patina have brought the material back into vogue. This popularity has been helped, no doubt, by environmental concerns associated with some modern coatings. A true lime wash contains zero volatile organic compounds (VOCs) and is completely made from natural materials.

With the resurgent popularity of lime wash, no doubt traditional masons of the future will be repairing and renovating coatings laid down in the early 21st century.

TM