by Sarah Marie Jackson, Tye Botting, and Mary Striegel
The results of the study are compiled
here to respond to the questions proposed
by the partners of the study and
listed in the scope of study.
Does the source of the lime affect the
durability of the limewash? On both the
wood and brick samples the limewashes
prepared using Graymont hydrated lime
and lime putty (washes A, B, D, L, and
M) performed better than the limewashes
prepared with the high-calcium
lime from the Mississippi Lime Company
or Virginia Lime Works (washes C,
F, I, K, and N). The limewashes prepared
with an acrylic-emulsion additive
had less notable difference in the performance
between lime sources (washes G
through I). This result could be due to
the powdery surface that was noted in
the adhesion tests on both brick and
wood samples.
Does the type of lime (e.g., hydrated
lime or lime putty) affect the durability
of the limewash? The type of lime
seemed to have less of an effect on the
durability of limewash in the test results
of unweathered wood samples. Taking
into account the standard deviation of
the test results, all wood samples performed
in the same range for each recipe.
Wash E, with the casein additive and
Graymont Niagara lime putty, performed
slightly better overall than the other
limewashes on wood samples.
The limewashes prepared from putty
performed better than those prepared
with hydrated lime on the brick samples
tested before and after artificial weathering.
For the handmade-brick samples the
limewashes prepared with putty and applied
without a primer performed better
than other limewashes.
Does the surface material, or substrate,
affect the adhesion or the resistance to
abrasion of limewashes? Limewash
performed better on brick samples than
on either epoxy or wood samples, indicating
that the substrate does make a
difference. On the wood samples the
limewash began flaking off as soon as it
dried, indicating poor adhesion, which
could have resulted from either the
closed-cell matrix or the expansion and
contraction of the wood. The limewash
on the epoxy samples performed statistically
similar to the wood samples of the
same washes. Pits created from the filler
being loosened during surface sanding of
the epoxy may have improved adhesion.
How do various additives and modifications
affect the performance of limewashes?
Limewashes prepared with salt,
alum, molasses, and laundry bluing had
the greatest solids deposit and performed
well in tests on unweathered samples
of all materials. These formulations
were also slightly darker in appearance
than the other limewashes, which could
have been a result of the salt or the
molasses individually or the interaction
of the two. After weathering, however,
these limewashes (washes A through C)
performed significantly worse on all
materials. This poor performance was
markedly noticeable on the brick samples
and could have been a result of salt
migration through the samples.
The limewashes prepared without
additives (washes K, L, M, and N) and
applied either with or without a primer
performed better than the limewashes
prepared with an acrylic or casein additive
on brick samples. On brick samples
the limewashes prepared without additives
or primer (washes L, M, and N)
performed best in tests after weathering.
The enhanced performance of the limewashes
prepared with no additives
suggests that these formulations continued
to carbonate during artificial weathering.
The decrease in performance of
limewashes that included additives
indicates that the limewashes lost durability
during artificial weathering, suggesting
that the additives may have
affected the limewash matrix or carbonation.
On the wood samples the limewashes
applied after a primer performed
better than those applied without a
primer.
Can acrylic-emulsion additives improve
or hinder the performance of limewashes?
The limewashes prepared with
an acrylic-emulsion additive (washes G,
H, and I) had a good appearance on all
materials. However, they also had the
least amount of solids deposited on all
samples. In both the adhesion and abrasion
tests before and after weathering
the limewash had a powdering surface.
The powdering and poor test results
could indicate disrupted or incomplete
carbonation.
How do limewashes behave after longterm
exposure to ultraviolet light and
temperature? On the wood samples the
limewashes deteriorated during artificial
weathering. Samples from washes A, F,
H, and I were too deteriorated after
weathering to continue with the abrasion
test. By way of contrast all brick
samples showed little visual change from
artificial weathering. For almost all
samples in washes A through K the
colorimetry revealed lightening of the
limewashes after artificial weathering.
As stated in the discussion of additives,
the limewashes prepared without additives
and applied without a primer to
the handmade brick (washes L, M, and
N) performed better after artificial
weathering. They were the best performer
in tests after artificial weathering.
However, limewash prepared with
salt additive (washes A, B, and C) experienced
a drastic decrease in performance
after artificial weathering.
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.