Background

by Sarah Marie Jackson, Tye Botting, and Mary Striegel

Historically, applying a sacrificial surface finish to buildings became more widespread in European countries after the seventeenth century as good hardwoods became scarce, necessitating the use of poorer quality building materials. ³ In the United States, a much younger and less populated country, limewash came into widespread use during the ninteenth century. Limewash continued to be used on plaster and more informal areas even after the advent of oil-based paints. ⁴

Traditionally limewash was prepared on-site by skilled craftsmen and applied in the spring or fall to take advantage of optimal temperatures. The basic ingredients in limewash are lime and water, although other ingredients were sometimes included to provide additional chemical or physical properties. The use of additives required careful consideration due to the possible adverse affects. For example historic recipes often called for adding tallow during slaking in order to increase water-shedding capabilities. The tallow did increase water shedding, but it also decreased breathability and the ease of applying successive layers.

Pigments were often added to limewash to vary the color of the finish. Earth-based pigments were used historically to maintain consistent color and limit changes from the alkalinity of the limewash. It was necessary to add pigments in moderation to limit the weakening effect of excessive amounts of additives.

In order to maintain consistency sufficient limewash to complete the project was mixed and agitated throughout application. ⁵ After the limewash was prepared, the surface to be treated was brushed down to remove loose dirt and then dampened to prevent the wash from drying too quickly. If the limewash dried too quickly, carbonation would be disrupted, resulting in a weak, cohesionless finish that tended to crack and powder.

Limewash was applied in thin layers, constantly maintaining a wet edge to create a more conformal coat. Multiple layers were applied, leaving sufficient time for drying between applications. Drying times were 24 hours or longer, depending on exterior conditions such as humidity and temperature. When first applied, the limewash appeared transparent, but as it carbonated and layers built up, it was transformed into a solid, matte finish. ⁶ Three or more applications were recommended for the initial limewashing. Annual reapplication was necessary to counter weathering from exposure. Successive limewashings required fewer layers. ⁷

It was only after the Civil War that ready-made paint began to gain popularity in the U.S. ⁸ Beginning in the 1900s limewash was used less often in urban areas, although its popularity continued in rural settings until as late as the mid-twentieth century. Urban areas were the first to be affected by an increase in the use of modern, long-lasting building materials and the rising cost of labor needed to apply limewash. The time needed to apply multiple thin layers and for carbonation may also have contributed to the waning popularity of limewash, as ready-made paint was less time- and labor-intensive.

Limewash is now beginning to see renewed interest, because its vapor permeability allows for greater water transfer than most modern finishes. This property is very important when considering finishes for historic structures where dampness is often a problem. The increased interest may also be attributed to historical accuracy, aesthetic qualities, and environmental concern (limewash produces very small quantities of volatile organic compounds).

Originally published in APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 38:2-3, 2007

Notes

1. Laura Soulliere Gates, email to author, Aug. 17, 2006.

2. National Park Service Technical Information Center, 'Class C' Cost Estimating Guide: Historic Preservation and Stabilization (Denver: Denver Service Center, 1993), 18.

3. Colin Mitchell Rose, Traditional Paints, available from http://www.buildingconservation.com/articles/paint/paint.htm.

4. Abbott Lowell Cummings and Richard M. Candee, "Colonial and Federal America: Accounts of Early Painting Practices" in Paint in America: The Colors of Historic Buildings 14 (New York: Wiley, 1994), 14.

5. Scottish Lime Centre, Technical Advice Note 15: External Lime Coatings on Traditional Buildings (Edinburgh: Historic Scotland, 2001).

6. Ibid.

7. John Ashurst and Nicola Ashurst, Mortars, Plasters, and Renders, vol. 3 of English Heritage Technical Handbook (Great Britain: Gower, 1995), 47.

8. Roger W. Moss, "Nineteenth-Century Paints: A Documentary Approach" in Paint in America: The Colors of Historic Buildings (New York: Wiley, 1994), 55.

9. ASTM Subcommittee D01.24, Standard Test Methods for Viscosity by Ford Viscosity Cup, ASTM D 1200-94 (West Conshohocken, Pa.: ASTM, 1996).

10. Marcy Frantom, email to author, Sept. 12, 2005.

11. ASTM Subcommittee D01.23, Standard Test Methods for Abrasion Resistance of Organic Coatings by Falling Abrasive, ASTM D 968-93 (West Conshohocken, Pa.: ASTM, 1996).

12. ASTM Subcommittee D01.23, Standard Test Methods for Measuring Adhesion by Tape Test, ASTM D 3359-95 (West Conshohocken, Pa.: ASTM, 1996).

13. ASTM Subcommittee D01.27, Standard Practice for Conducting Tests on Paint and Related Coatings and Materials Using a Fluorescent UV-Condensation Light- and Water- Exposure Apparatus, ASTM D 4587-91 (West Conshohocken, Pa.: ASTM, 1996).

14. Pete Sotos, conversation with author, Nov. 15, 2006.

15. Ruth Johnston-Feller, Color Science in the Examination of Museum Objects: Nondestructive Procedures (Los Angeles: Getty Conservation Institute, 2001), 35.

16. L. Franke and I. Schumann, "Causes and Mechanisms of Decay of Historic Brick Buildings in Northern Germany," in Conservation of Historic Brick Structures, ed. N. S. Baer, S. Fitz, and R. A. Livingston (Shaftsbury: Donhead, 1998), 26-34.

SARAH MARIE JACKSON joined NCPTT in 2005 as a graduate intern to continue the testing for the limewash study. In 2006 she accepted a permanent position with the Architecture and Engineering Program at NCPTT. She received a master’s degree in historic preservation from the Savannah College of Art and Design.

TYE BOTTING is a research staff member at the Institute for Defense Analyses. He served as the NCPTT/NSU joint faculty researcher for three years. He holds a PhD in nuclear chemistry from Texas A&M University, where he did post-doctoral work in nuclear engineering.

MARY STRIEGEL is responsible for NCPTT’s Materials Research Program, focusing on evaluation of preservation treatments for preventing damage to cultural resources. She also directs investigation of preservation treatments geared towards cemeteries and develops seminars and workshops nationwide. She holds a PhD in inorganic chemistry from Washington University in St. Louis.