by Valentina Puglisi
The cleaning of
architectural surfaces has long been and still is a controversial issue
that gives place to long debates among art historians, architects and
restorators. There is a real difficulty in reaching mutual understanding
and identifying stable limits and references as to the various questions
that such issue entails. This is due to a poor knowledge of the mechanisms
arising between stony materials and interacting environmental agents,
to the difficulty in finding lab results that are valid for the material
at stake, and to the variety of the situations experts must analyse
- as there is a great number of variables at stake and the possible
synergies that may link them can greatly complicate both the diagnostic
and the operative choices.
Architectural surfaces, especially in a restoration context, cannot
refer to a unitary concept that would be tacitly accepted by all. Nor
are the operative “philosophies”, which underlie our idea
of cleaning, safe from conceptual and methodological traps.
In the framework of the conservation of architectural manufacts, surface
has a double value. On the one hand, it can be defined as an exteriority
able to transmit the objects’ symbolical contents and thus, include
the most various features, such as forms, colours, brightness and roughness.
On the other hand, it is a “thin layer”, characterized by
a specific materic consistency and objective intrinsic features and
linked to alteration phenomena that shall be analysed during the operative
step.
Both meanings seem clear from an abstract point of view but they get
more complicated when the idea of architectural surface is coupled with
the concepts of “alteration surface” and “additional
layer”: in the first case, ambiguity comes from the fact that
decay phenomena touch the materic consistency of the stony surface,
whether adding or removing features, so that it is not always possible
to determine the line dividing the two materials in the new physical-chemical
balance; on the contrary, in the second case, surface already defines
itself as a “negative film” and, inside a more or less variable
thickness, some undergoing processes are aimed at removing progressively
the subsequent surface layers.
All issues related to surface are particularly relevant because of the
obvious impact they have on aesthetic assessment: after all, what is
at stake is the image of the manufact.
