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A unique property of copper as a construction material
is its characteristic coloring.
The coloring of copper is heavily dependent on the atmosphere
present in which the building is situated.
In particular, the natural weathering of copper to blue-green
(or grey-green) is a result of airborne sulfur compounds.
The quantities of these compounds can vary substantially.
For example in industrial and sea-coast environments,
a natural patina may occur in five to seven years. However,
in rural atmospheres, the quantity of air-borne sulfur
dioxide is relatively low and hence a natural patina may
occur after ten to fourteen years.
The table below has been provided by the Copper Development
Association (1993, p.57) and is a general overview of
the natural weathering process.
Please note that this is provided as a guide only as
the actual time frame required to achieve a particular
coloring is dependent on the atmospheric conditions.
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