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The growing effort in conservation to characterize the
condition of skin, hide, and leather materials now includes
a powerful new tool for quantifying deterioration and
documenting structural change due to treatment and storage.
CCI has recently developed a quantitative image analysis
technique that radically improves the precision and accuracy
of microscopical shrinkage temperature measurements (a
method that CCI introduced to conservation in 1990).
The original method measures the molecular thermal
stability of minute sample quantities of collagen fibres
extracted from a skin or leather. The samples are heated
in water from room temperature to a maximum below boiling
to determine the temperature range over which the fibres
undergo a natural process of structural collapse and
visible shrinkage. The more deteriorated the sample
fibres, the lower the temperature range of this collapse.
The new quantitative image analysis technique captures
an image every quarter degree Celsius during heating,
so that fibre shrinkage is transformed into a digital
process comprising millions of image pixels. This new
digital quantification proceeds through four stages:
(1) separation of the pixels representing the fibres
from those of the background, (2) conversion of the
background pixels to zero intensity followed by (3)
summation of the pixels representing just the shrinking
parts of the fibres over each quarter degree temperature
interval, and, finally, (4) plotting the counts in a
graph. The resulting curve precisely marks the beginning
and end of fibre collapse.
The new technique is currently being used to measure
the preservation of the 10th century Archimedes Palimpsest,
the oldest existing writings of many of Archimedes’
theorems. Other significant parchment documents are
also being studied.
Incorporating quantitative image analysis into thermal
stability measurements has produced a truly objective
analytical technique, one that has tremendous value
for a broad range of research and conservation applications
for skin and leather materials in museums, galleries,
and archives. CCI plans next to employ the technique
to characterize the effects of humidification on semi-tanned
skin garments of First Nations.
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