Keystone Preservation Group
Historic Preservation, Architectural Conservation, Scope Consultation, RITC Consulting
Historic Preservation, Architectural Conservation, Scope Consultation, RITC Consulting
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Analysis of Historic Mortars, Plasters and Stuccoes
Keystone regularly completes compositional analyses for composite materials
such as mortars, plasters and stuccoes from historic buildings. The primary
objective of mortar analysis varies from project to project. In some cases,
mortar analysis is required to obtain project funding. In others, it is intended
to provide information on the evolution of and changes made to an historic
property over time; this can be especially critical for HSRs or preservation
plans in addressing buildings whose history is not completely understood.. In
many cases, mortar analysis is intended to provide base information on which
new repair mortars can be based.
Standardized tests produce numerical data which requires interpretation;
however, similar data can be produced by compositionally dissimilar materials.
Therefore, the knowledge and breadth of experience of the analyst is a critical
component of mortar analysis. Over the course of a decade and a half, our
conservation staff has analyzed more than 600 historic composite materials,
regularly employing the following analytical techniques:
Jedrzejewska calcimeter method: This technique essentially breaks down a
sample into constituent parts and provides data on the nature of the binder by
gauging the extent of its reaction with hydrochloric acid. Analysis provides
quantifiable data on quantities of calcium carbonate, soluble silicates and solids
which is compared with published experimental standards to produce
volumetric information for lime, cement and sand.
Basic compositional and visual analysis: Mortars based on different materials
(lime, clay, cement and pigments) not only look different, but have different
reactive characteristics. With this technique, basic acid digestion and visual
assessment can provide information on the components present within a
particular mortar mix.
Aggregate matching: Original sands are extracted and isolated, and
contemporary aggregates provided to match their color and gradation.
Replication mortars: We are often asked to produce replication discs to
exactly match the color, texture and composition of the original mortars; doing
so can often save time which would otherwise be spent for quality mock-ups
during construction.
Keystone regularly completes compositional analyses for composite materials
such as mortars, plasters and stuccoes from historic buildings. The primary
objective of mortar analysis varies from project to project. In some cases,
mortar analysis is required to obtain project funding. In others, it is intended
to provide information on the evolution of and changes made to an historic
property over time; this can be especially critical for HSRs or preservation
plans in addressing buildings whose history is not completely understood.. In
many cases, mortar analysis is intended to provide base information on which
new repair mortars can be based.
Standardized tests produce numerical data which requires interpretation;
however, similar data can be produced by compositionally dissimilar materials.
Therefore, the knowledge and breadth of experience of the analyst is a critical
component of mortar analysis. Over the course of a decade and a half, our
conservation staff has analyzed more than 600 historic composite materials,
regularly employing the following analytical techniques:
Jedrzejewska calcimeter method: This technique essentially breaks down a
sample into constituent parts and provides data on the nature of the binder by
gauging the extent of its reaction with hydrochloric acid. Analysis provides
quantifiable data on quantities of calcium carbonate, soluble silicates and solids
which is compared with published experimental standards to produce
volumetric information for lime, cement and sand.
Basic compositional and visual analysis: Mortars based on different materials
(lime, clay, cement and pigments) not only look different, but have different
reactive characteristics. With this technique, basic acid digestion and visual
assessment can provide information on the components present within a
particular mortar mix.
Aggregate matching: Original sands are extracted and isolated, and
contemporary aggregates provided to match their color and gradation.
Replication mortars: We are often asked to produce replication discs to
exactly match the color, texture and composition of the original mortars; doing
so can often save time which would otherwise be spent for quality mock-ups
during construction.
Deteriorated mortar: American Tobacco
Clay stucco: Black Horse Inn
Pigmented mortars: Fort Christian
Clay lime mortar: Gutelius House
Replication: University Cottage Club
Replication: University Cottage Club
