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deposits of dark material accumulate in depressions, while
exposed surfaces become polished or bleached, the result
is a characteristic light-dark contrast that asserts plasticity
through height and depth.
Achieving expression in the process, first, are general
characteristics of location or orientation. To the extent that
individual areas are exposed to weathering, the differences
between horizontal and vertical surfaces, between protected
parts and weather-side, become visible. Second, the specific
structural properties of the > materiality become clearly per-
ceptible. With age, for example, the growth layers of soft
woods become increasingly visible as relief in depth. Oxidiz-
ing metals, on the other hand, develop a specific coloration
and form particular surface structures, rust being an example.
Depending upon hardness and composition, natural stone
erodes, is covered in moss, or becomes polished. Such changes
render time perceptible through the perishable character of
buildings; and buildings become capable of registering the
passage of time.
Alongside effects of contrast, patina often has a commu-
nicative function. As the irruption of nature, it softens the
artificiality of new surfaces through plant growth and other
natural alterations, enlivening them and linking surfaces with
one another, as well as with the surroundings, through unify-
ing influences. A sense of familiarity with new housing estates
is facilitated by the ‘growing in’ process that is fostered by
progressing vegetation.
Patina also emerges as traces of > use. As a means of ex-
pression, it tells of consumer habits, for example through nic-
otine deposits. The nature and intensity of utilization becomes
visible through polished door handles, worn steps, thresholds
and threadbare floorings, just as wall areas formerly occu-
pied by pictures are betrayed by their contrasting paleness.
Such traces are among the enduring changes individuals leave
behind on the surfaces of architecture. In the broadest sense,
they include the more-or-less skilful repair of damaged areas,