September 2002, I attended the annual gathering meeting for The
Building Limes Forum held in Kilkenny, Ireland. It was there that
Mr. Revie showed the slides for these photos which depict the open
pore structure these mortar ratios have by the presence of a blue-dyed
epoxy resin first injected. The blue in the photos clearly shows
that traditional lime putty and Natural Hydraulic Lime mortars have
superior open pore structures. An open pore structure allows a high
level of liquid and vapor permeability, which should be maintained
when mortar is used to cement historic brick and stone together.
Water can be absorbed quickly through an open pore structure and
also evaporates back out very easily.
rainwater gets into a wall through absorptive brick and stone that
has been repointed using Portland cement mortar or through its shrinkage
cracks, water quickly wicks to the original lime and sand bedding
mortar. Then the water must egress back out through the face of historic
brick and stone, thereby accelerating their deterioration. If it can't
evaporate out, trapped water may migrate into interior spaces, possibly
causing interior damage.
My children loved the sweaters and leprechaun
trinkets that I brought back for them. However, when I showed the
mortar photos by William Revie and explained the damaging effects
Portland cement repairs made to historic buildings during the last
50 years in contrast to the thousands of years of success builders
have had using lime mortars, their reactions were similar to those