by Sarah Marie Jackson, Tye Botting, and Mary Striegel
The purpose of the study was to test a
variety of limewash recipes for possible
use on historic brick and wooden structures
located in CARI. The immediate
goal was to identify lasting, low-cost
limewash that could be applied in approximately
three layers and would last
three to five years. NCPTT partnered
with CARI to determine the durability
of traditional and modified limewash
recipes within certain criteria. In collaboration
with the project partners,
NCPTT designed a program of testing
for limewash on weathered wood,
rough-sawn wood, handmade brick,
and modern brick.
A variety of limewash recipes was
tested on multiple sample materials for
possible use at CARI. Based on the
results, the most important distinction
among the recipes tested was the additives
used, rather than the type of lime.
The recipes fell into four different categories:
salt and molasses additives, casein
binder, acrylic binder, and no additives.
The adhesion of the limewash was greatly
affected by the substrate to which it
was applied. The more porous material,
brick, allowed for a better adhesion of
the limewash, creating a more cohesive
coat and increasing durability.
On porous materials such as brick,
soluble salts can be very detrimental,
contributing to spalling or flaking and
micro-fissures in the pore walls, increasing
drying times, and changing the
porosity of the brick. 16 Therefore, limewash
prepared with a salt additive may
be detrimental to porous materials. Such
formulations did not perform significantly
better than limewash prepared
without additives after artificial weathering
and actually experienced a significant
decrease in performance on both
abrasion and adhesion tests after artificial
weathering. However, on the handmade
brick wash M performed almost
twice as well on all tests after artificial
weathering. The porous structure of
handmade brick makes a primer unnecessary
to assist in the adhesion of limewash
to the surface. For application on
handmade or historic brick wash M
(Graymont Niagara lime putty and
water) would likely provide the best
results in field applications.
None of the limewashes tested were
long-lasting on the wood samples, which
could be attributed to using only three
layers of limewash on the wood samples.
The wood itself has been unfinished
for numerous years, which most
likely contributed to the poor adhesion
and would have affected any finish
applied to it. However, there was a
noticeable difference performance between
the washes applied after Edison
Coatings Primer #342 and those that
were applied to bare wood. The limewashes
applied to wood samples after
primer performed better during study.
In applications where an acrylic primer
is deemed an inappropriate treatment on
wood, wash E with Graymont Niagara
lime putty and casein would likely be a
good choice for use. The epoxy samples
experienced results that were comparable
to the same recipes on the wood
samples, indicating they would have a
similar durability. Wash E (the Graymont
Niagara lime putty, water, molasses,
clove oil, and laundry bluing) was
the best performer on the wood and
epoxy samples.
Future Research Questions
Additional research is needed on the
physical and chemical properties of
limes available commercially in the
United States and Europe in order to
gain a clearer understanding of their
role in limewash. Application of a
greater number of thin coats of the
wash, as well as investigation of the
effects of temperature and humidity on
carbonation, may provide greater insight
into the durability of limewash.
The use of Pozzalonic additives and the
interaction between the minerals in the
brick and the limewash should be studied
for historical accuracy and possible
increased durability. The reversibility of
primer and its effect on historic materials
should be researched more thoroughly
before considering it for use.
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.