Laboratory Analysis. Laboratory analysis plays a scientific
role in the more intuitive process of architectural investigation. One
of the most commonly known laboratory procedures used in architectural
investigation is that of historic paint analysis. The chronology and stratigraphy
of applied layers can establish appropriate colors, finishes, designs or
wall coverings. When conducted simultaneously with architectural investigation,
the stratigraphy of finishes, like that of stratigraphic soils in archeology,
helps determine the sequence of construction or alterations in a building.
Preliminary findings from in situ examinations of painted finishes
on walls or trim are common, but more accurate results come from extensive
sampling and microscopic laboratory work using chemical analysis and standardized
color notations. Consultants without the proper knowledge have been known
to cause far more harm than good.
Mortar and plaster analysis often provide a basis for dating construction
with minimal intervention. Relatively small samples of the lime-based materials
can be chemically separated into their component parts of sands and fines,
which are then visually compared to equivalent parts of known or dated
samples. A more thorough scientific approach may be used to accurately
profile and compare samples of other materials through elemental analysis.
Two similar methods in common use are Neutron Activation and Energy Dispersive
Spectroscopy (EDS). Neutron Activation identifies the sample's trace elements
by monitoring their response to neutron bombardment. EDS measures the response
to electron bombardment through the use of an electron microscope. In both
tests, the gathered information is plotted and matched with the reactions
of known elements. The results provide a quantitative and qualitative profile
of the sample's elemental components for use in further comparisons.
Dendrochronology presents a minimally destructive process for dating
wooden members. Also called tree ring dating, this process relies on the
comparative wet and dry growth seasons of trees as seen in their rings
via a core sample. This technique has two limitations: a very extensive
data base must be compiled for climatic conditions over a long span of
years and matched with corresponding tree ring samples; and the core samples
can only be taken from timber which still has a bark edge. Simple identification
of wood species during an investigation can be determined from small samples
sent to a forest products laboratory.