Any recommendation for field application based on the results of this data must take into
account the dynamic of moisture migration in masonry walls and processes such as efflorescence
and subflorescence that may affect the choice of the ideal coating. Efflorescence is when salt
appears on the surface of materials and subflorescence is when salt crystallizes beneath the surface
of a material. Subflorescence is created when soluble salts in a liquid travel through a brick until
temperature and atmospheric pressures cause the liquid to evaporate leaving behind the salt crystal
deposits in the interior voids of a brick.1 Soluble salts can be very detrimental to bricks contributing
to physical problems such as spalling or flaking, increasing dry times, changing porosity, and micro
fissures in the pore walls.2 Soluble salts can transfer naturally through rising damp, pollution in the atmosphere,3 mortar used to set the bricks, adjacent materials, or be present from the clay used in the
brick construction.4 We would recommend not introducing more salt to brick structures by using a
limewash recipe that contains salt. During the artificial weathering process the modern brick
samples with washes A, B, and C all experienced significant efflorescence on the side opposite of
the limewash. We did not note any efflorescence on the historic brick, but that could have been
affected by several factors such as porosity.
Although Wash A performed the best on the handmade brick and Wash B performed the best
on the modern brick we feel that using a recipe with a salt additive could be detrimental to the
bricks. Wash K performed well on both handmade brick and modern brick and is our
recommendation for use on the brick structures at Cane River Creole National Historical Park.
Wash K consists of Virginia Lime Putty and water and has no additives that could be detrimental to
the brick.
Alternative limewashes include washes D and E. Wash E performed well on the handmade
brick and is in the group of top performers, but on the modern brick it performed in the middle of the
group. Wash D rated as the second best performer on the modern brick, but on the handmade brick
it falls in the middle of the group.
It should be noted that all samples were subjected to color analysis before and after artificial
aging. All limewashes display some color change over time and tend to darken and yellow. Since
all washes changed approximately the same, we did not include these tests in our recommendations.
1 Weaver, Martin E. with F.G. Matero, Conserving Buildings: guide to techniques and materials (New York, John Wiley
& Sons, 1993), 120.
2 Franke, L. and I. Schumann, "Causes and Mechanisms of Decay of Historic Brick Buildings in Northern Germany," in
Conservation of Historic Brick Structures, eds. N.S. Baer, S. Fitz, and R.A. Livingston (Shaftsbury: Donhead, 1998), 26-
34.
3 Caner-Saltik, E.N., I. Schumann, and L. Franke, "Stages of Damage in the Structure of Brick Due to Salt Crystallization," in
Conservation of Historic Brick Structures, eds. N.S. Baer, S. Fitz, and R.A. Livingston (Shaftsbury: Donhead, 1998), 49.
4 Ashurst, John and Nicola, Practical building conservation: English Heritage technical handbook, vol. 2 Brick, Terracotta,
and Earth (Aldershot, Gower, 1995), 50.