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T W E N T Y T H I R D E D I T I O N
3.3
STRUCTURE & FABR I C :
ME TAL ,
WOOD & GLASS
or similar material and left for a period of
hours, or days for thick layers, before being
removed. Being absorbent, the poultice draws
off the paint layer, most of which peels off
with the poultice. The residue may then be
removed with water and a scrubbing brush.
Because no scraping is necessary it is possible
to completely remove paint even from ornate
work without any damage, and it is quite an
effective method for drawing paint out of the
wood grain.
Alternatives to poultices include
gels and pastes which are thick enough
to be used on horizontal ceiling beams
and are often thixotropic – that is to
say that they become more fluid when
agitated and less fluid when left.
Some of these chemicals are alkali-based
and can be highly caustic, while others are
solvent based, so it’s important to carefully
consider the environment in which they
are being used and the health and safety
precautions required. This may include the
need to ensure that the area is well ventilated
and that the correct personal protection
is used. Water-based products with a low
VOC (volatile organic compound) content
are available which are less damaging to
human health and can be used in areas where
ventilation is poor.
SELECTING THE APPROPRIATE
METHOD
There are many factors to consider when
selecting the most suitable method – more
than can be covered in full here. Some of the
key considerations are explored below.
CONSERVATION CONSIDERATIONS
These should include the level of damage
that the process causes to the surface of the
substrate and any markings, carvings or
mouldings; and the degree to which it raises
the grain or otherwise alters the aesthetic
appearance of the timber. The impact on
associated adjacent materials such as glass,
brick and plaster should also be considered.
The ability to control the method and
to remove individual layers of paint without
damage to earlier finishes is key, as is the
ability to vary the aggressiveness of the
method according to characteristics of the
timber such as the degree of heartwood and
sapwood, or whether the timber is sound or
has suffered decay.
The requirement for an experienced and
skilled operative is a practical consideration but
also has conservation implications because a
method deemed suitable in the right hands may
be highly damaging in the wrong ones.
PRACTICAL CONSIDERATIONS
The ability to use the method in an enclosed
space is a key consideration, not only in
terms of health and safety but also in its
impact on the work of other trades on site.
There are of course many other health
and safety implications, such as the use of
personal protective equipment and the need
to work at height as well as the requirement
for training, risk assessment and COSHH
(Control of Substances Hazardous to Health)
considerations. The effect of chemicals and
blasting media on the environment should
also be taken into account.
The various complications of in situ use
should also be considered, such as working on
the underside of ceiling joists, working outside
in bad weather and working in buildings that
need to remain habitable during the works.
Finally, cost should be considered.
In a commercial industry this is a key
consideration which few clients can ignore,
and while it should not be the overriding
factor in selecting a paint removal method,
clearly it will influence decisions.
LET THE BUILDING SPECIFY THE REPAIR
Every circumstance will be different and the
variables of the specific site should be used to
determine the most suitable method.
The various advantages and disadvantages
of the methods and their suitability on
different paints and substrates should be
balanced and, where necessary, the use of
more than one method should be considered.
For example, the project might be a full-
building renovation which is scheduled to
include paint removal from a heavily moulded
spine beam supporting closely spaced joists in
a large hall. In this context, one might select
a chemical poultice remover for its ability
to remove the paint from the moulded areas
of the spine beam where dwelling with an
aggressive mechanical method could cause
damage. This might be followed by low-
pressure air or air/water abrasive blasting
on the flat areas only, by a highly skilled
operative, so that the work can be completed
more quickly, and in the knowledge that the
building will be cleaned thoroughly before
completion of the works.
In the same circumstances but
where the building will remain habitable,
sandblasting could be replaced with dry
ice blasting, which is a fast and relatively
clean method with no expelled aggregate
(although it is likely to cost more).
In all cases a test patch should be
carried out. This should be used to provide
a specification for the paint removal
which should then be presented to the
relevant conservation body (usually the
local authority conservation officer)
and permission for the works should be
sought. The works must then be carried
out in accordance with this specification
and by a skilled and trained operative.
One of the governing principles of timber
frame repair can equally be applied to the
removal of paint. When repairing timber one
should look at the species, type and method
of conversion, speed of growth and direction
of grain of the host timber in order to specify
a suitable repair timber. This ethic of letting
the building specify the repairs can equally be
applied to paint removal.
Finally, it is also important to bear in
mind that the painted surface being removed
may also be of archaeological value as the
stratigraphy of the paint will give a historical
record of the decoration. There is clearly a
value therefore in keeping representative areas
of paint, perhaps in inconspicuous areas to
preserve this evidence in situ.
BEN KIRK
MSc is a consultant specialising
in the repair and conservation of
timber framed buildings and director of
Creative Heritage Ltd based in West Sussex
(see page 50). His particular interests are
rural dwellings and farm buildings.
Timber surface before and after chemical poultice application
Dry ice blasting equipment
Hopper used for a low pressure vortex system, similar
to that used in sandblasting