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UNDERSTANDING AND
CONSERVING TERRACOTTA
CERAMIC STANDARDS
Conservation Officers in most towns
and cities wifi be confronted with build-
ings faced in terracotta. Some will be
listed but most depend on being in
conservation areas for any protection.
Terracotta - comprising large blocks
and slabs of moulded clayware - was
used most widely on commercial and
public architecture dating to the late-
19th and early 20th centuries. Such
buildings have to earn their keep.
Owners will expect any refurbishment
to create a bright and commercially
more attractive appearance. Costs will
be vetted carefully against increased
value or rentals. Only in exceptional
cases can grant-aid be used to encour-
age the highest standards in any con-
servation project.
In this situation where
conservationists have to work hard to
convince owners, architects and
builders of the need for sensitivity, the
challenges presented by terracotta are
compounded by the fact that there is
still widespread ignorance about the
nature of different types of architectural
ceramic, and the merits and dangers of
different approaches to cleaning.
This depressing scenario can be
Dr Michael Stratton
discusses the essential features
of the material

taken further. Most of the key examples
ofterracotta architecture in Britain have
been irreparably damaged not by
pollution or decay but by human
intervention in the name of
conservation. The fireskin and much of
the decorative detailing on the Royal
Albert Hall was blasted away by grit
cleaning in 1972, and the surface of the
nearby Natural History Museum was
scored and bleached by hydrofluoric
acid a few years later. This trail of
abrasive destruction continues, with
some commercial buildings now being
cleaned every 3-5 years, as the rate of
soiling increases due to loss of the
smooth protective fireskin.
A new British Standard for the
conservation of terracotta is awaited.
Until it is ready, only broad principles
can be put forward, along with a series
of cautions about the damage which
can inadvertently result from decisions
over cleaning and partial replacement.
This article urges a more conservative
approach; offers some guidelines as to
how Conservation Officers can try to
understand ceramic architecture and
the nature of terracotta; to then guide
owners and architects through the maze
of different technologies and options.
UNDERSTANDING TERRACOTTA
As a prelude to any recommendations
or decisions, one needs to understand
the nature of the material and the con-
text in which it was used. Unglazed
terracotta, typicallywith a natural colour
of buff, grey or red, was made in the
Tudorperiodbut then, farmorewidely,
from the late 18th century. It can be
readily distinguished from glazed fai-
ence, where the body is covered by
one or more glazes. Confusion only
arises with some of the vitreous fin-
ishes dating to the turn of the century,
where a clear, matt glaze was applied
to the fired body. Faience became
widely used from the 1890s. The most
usual colour for faience was a white or
cream, bright polychromy inspired by
Art Nouveau and Art Deco being re-
served for more exotic projects. The
unglazed surface of terracotta may be
more vulnerable to soiling and is hence
often the subject of more vicious clean-
mg - buttheprotectivefireskin, achieved
by smoothing over a block once it has
been extracted from the mould and by
giving it a full, high-temperature firing,
is the key protective shield for the
piece, as well as giving it its distinctive
colour and texture.
To understand the nature of the
surface, be it fireskin or glaze, it is
necessary to appreciate the nature of
the body, which, in turn, will depend
on the clays used by the manufacturer.
In most simplistic terms, firms either
worked a single clay or created a
mixture which (once mixed with
water) would have a smooth texture
and plasticity. Terracotta clays had to
carry fine detail and then be fired to a
high temperature without distortion
or excessive shrinkage.
During the Tudor period, young sur-
face clays from the south east of Eng-

Building by numbers: hollow blocks of
terracotta being set onto brickwork for the
Bournemouth Pavilion, c1930.
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CONTEXT 52

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