on Historic Surfaces
historic graffiti on a timber door at Edinburgh Castle
by French prisoners during the Napoleonic wars
term graffiti derives from the Italian graffio meaning 'scratching'
and can be defined as uninvited markings or writing scratched
or applied to objects, built structures and natural features.
It is not a new phenomenon: examples can be found on ancient structures
around the world, in some cases predating the Greeks and Romans.
In such circumstances it has acquired invaluable historical
and archaeological significance, providing a social history of
life and events at that time. There are also examples which have
been elevated from acts of vandalism to works of art. In April
2007, a mural by Banksy near Old Street Station in central London,
was valued at £200,000 when it was painted over in error. However,
such examples are extremely rare. Graffiti is now a problem that
has become pervasive, particularly over the last 50 years, as
a result of the availability of cheap and quick means of mark-making.
These include biros, felt and marker pens, correcting fluid, stickers
as well as the ubiquitous spray paints.
usually considered a priority to remove graffiti as quickly as
possible after it appears. This is for several reasons. The first
is to prevent 'copy-cat' emulation which can occur rapidly once
a clean surface is defaced. It may also be of a racist or otherwise
offensive nature and many companies and councils have a policy
of removing this type of graffiti within an hour or two of it
being reported. Also, as paints, glues and inks dry out over time
they can become increasingly difficult to remove and are usually
best dealt with as soon as possible after the incident. Graffiti can also lead to more serious forms of vandalism and,
ultimately, the deterioration of an area, contributing to social
Although graffiti may be regarded as an eyesore, any
proposal to remove it from sensitive historic surfaces should
be carefully considered: techniques designed for more robust or
utilitarian surfaces may result in considerable damage.
event of graffiti incidents, it is important that the owners of
buildings or other structures and their consultants are aware
of the approach they should take in dealing with the problem.
Some owners may wish to attempt their own treatment. Others may
prefer to appoint a suitable specialist contractor to deal with
the incident. Whichever course is chosen, it is important
that all those involved follow as far as possible a systematic
approach which includes such considerations as putting in place
preventive measures. The following course of action is recommended
when a graffiti incident is encountered:
- Record details of the
graffiti (the type of media used, the area affected, the type
and condition of the surface it is on) and the time and manner
of its execution, if known.
are useful to record graffiti incidents and may assist the police
in bringing a prosecution. Such images are also required for insurance
claims, and can be helpful to cleaning operatives, allowing them to see the problem
area before arriving on site.
- The police should be informed as
there may be other related attacks occurring locally. An incidence
pattern can identify possible culprits, as can stylised signatures
or nicknames, known as 'tags', which may already be familiar to
- Owners of listed or scheduled buildings or monuments
must contact the relevant heritage body or their local authority
planning office, and inform cleaning contractors of its status
before any trials take place.
- Having established that cleaning
can take place, do the owners feel confident in carrying out the
work themselves or should they seek professional help? This question
is dependent on the individuals, the scale of the graffiti, and
the type and condition of the surface it is applied to.
- The next
step is to carry out cleaning trials. These usually involve testing
a range of treatments, and are carried out on a small unobtrusive
area, if possible. Cleaning trials should always start with the
least aggressive method, usually water, and stop once a successful
method has been found. Test results and methodology should be
noted for future reference.
- Treatment of the area should begin once the cleaning trials have established the most
effective method. Care
should be taken to comply with health and safety legislation with
regard to the protection of both passers-by and any person carrying
out the cleaning. Operatives should follow product guidelines
in terms of application and removal, and wear the appropriate
protective equipment. Measures must be taken to ensure that run-off,
aerial mists, drips and splashes do not threaten unprotected members
of the public.
- If graffiti is expected to be repeated in a particular
location it is wise to consider a removable, sacrificial, barrier-coating
system as a form of preventive measure. This will not stop graffiti
being applied but will make its removal much more effective and
straightforward. Other preventive measures include Neighbourhood
Watch schemes, improved lighting, CCTV, physical barriers such
as gates and fences, and hard and soft landscaping.
example of early graffiti carved by the Vikings into the walls
of the Neolithic tomb at Maes Howe on Orkney
The type of
cleaning required is dependent on two main factors: the media
used (spray-paint, felt pen or enamel paint, for example); and
the type of material that has been defaced (such as stone, metal,
wood or plastic). The interaction of these factors must be considered
when selecting the best cleaning method. For instance, solvents
that will remove particular paints or inks from historic masonry
may damage paintwork or plaster.
Generally speaking, the more
porous the material onto which the graffiti is applied the more
difficult it will be to remove without causing damage. In the
case of a material such as stone, pigments are carried by the
solvent in which they are suspended through capillary action well
into the body of the material where they are hard to get at. This
is particularly true in the case of aerosol paints.
In this situation
a solvent/poultice-based treatment is about the only method that
can be used if damage to the surface is to be avoided. Abrasive
and other mechanical systems will only ever successfully remove
the graffiti from a porous substrate by first removing a layer
of the substrate material.
The type and
condition of a stone, brick, concrete, wood or metal substrate
may also determine what form of cleaning is possible. In some
cases it may be advisable not to clean off, but to cover over,
particularly where the substrate already has a covering of paint.
Removing graffiti from stone or other building surfaces may also
remove the patina of surface grime and pollution products on the
rest of the stone surface. This can result in a patchy appearance,
although in some cases the cleaned area can be graded into the
surrounding masonry to give a more subtle tonal transition. Alternatively,
in extreme cases, it may be preferable to clean an entire wall
or elevation so that the finish is consistent.
It is important
to be aware of other historic finishes that may be present on
top of the stone, such as plaster and pigments, as these may be
damaged by attempts to remove any graffiti.
OF CLEANING AVAILABLE
a variety of methods that are used to remove graffiti. Broadly
these divide between chemical and mechanical systems.
preparations are based on dissolving the media; these solvents
can range from water to potentially hazardous chemical 'cocktails'.
Many companies produce proprietary graffiti-removal products,
most of which will be based on similar solvents. The final choice
should be based on small site trials. Certain chemicals can be
used in conjunction with an inert poultice material, in which
case the chemical is usually applied first to dissolve the pigment,
followed by the poultice to draw the pigment in solution out of
the substrate. Repeated applications of the poultice and solvent
may be necessary to reduce the concentration of pigment in the
substrate to an acceptable level.
systems such as wire-brushing and grit-blasting attempt to abrade
or chip the media from the surface. These include a variety of
wet or dry air-abrasion systems using a broad range of abrasive
media, from very coarse materials such as aluminium oxide through
to fine talc. However, even at low pressure these air-abrasive
systems can easily damage the surface beneath, particularly brick
and stonework, so they are usually used by conservators to remove
superficial dirt only. Air abrasives and other mechanical techniques
used on their own are unlikely to be suitable for removing graffiti
caused by repeated and inappropriate removal treatments
Lasers of the Nd:YAG wavelength have also been used
with some success, particularly for the removal of graffiti from
light-coloured substrates. This is because the light is absorbed
by the pigmented layer of the graffiti, causing rapid expansion
and ejection. As very little energy is absorbed by the substrate
itself, controlled use of a laser by a specialist is less likely
to have a significant effect on the substrate than conventional
methods. The advantage is that there is no direct mechanical contact
with the surface, allowing very fragile surfaces to be cleaned.
However, its high cost means that use of this technology is largely
confined to the most important monuments.
When examining a graffiti
incident it is important to assess the ability of the substrate
to withstand the prescribed treatment. If there is any doubt regarding
this, then small trial areas should be undertaken to assess the
impact of more extensive treatment.
As with any
treatment, the success or otherwise of graffiti removal, and its
potential to cause damage, always rests with the skills of the
person undertaking the work. A reputable graffiti removal company
will have well-trained staff who understand the importance of
not damaging the substrate. It will also have a range of cleaning
methods at its disposal so that the correct treatment can
be selected for each circumstance. In the case of very sensitive
historic surfaces, a conservator with a background in the material
from which the graffiti is being removed should be consulted for
historic buildings may wish to consider tackling the graffiti
themselves and if this is the case there are free guides available
to assist in the process.
Personal protective equipment is required
for most graffiti-removal treatments. This may vary from the use
of rubber gloves to full protective gear, including full hand
and face protection in case of splash-back, and solvent mask to
prevent inhalation. Reading the manufacturer's instructions or,
better still, the pertinent 'technical data sheet' for the product
(available free on request from all chemical manufacturers) will
enable the correct protection to be used.
More often than not,
the products developed for paint removal are hazardous to the
environment and the resultant post-cleaning residues or run-off
are required to be disposed of in a specific way. In particular,
where there is a possibility of chemical residues getting into
water or drainage systems, proper control and disposal is essential.
The technical data sheet for the product will give the recommended
means of disposal. Alternatively contact the manufacturer directly
for advice on this subject. Local authorities will also be able
to provide guidance on the safe disposal of waste products.
on rubble masonry
where there is a recurring problem of graffiti attacks, local
authorities and estate managers will find preparing a policy or
strategy to deal with future incidents well worthwhile. This will help
individuals who are responsible for dealing with the problem by
providing them with a clear set of guidelines.
In dealing with
the graffiti problem, a combination of detection through regular
inspections and deterrence through the use of preventive strategies
should form the basis for a coordinated response to the problem.
of preventive strategies can be adopted to combat a recurring
problem of graffiti at a given site. It is also clear that preventive
measures will ultimately be cheaper, more effective and less damaging
than multiple removal treatments.
It is worth undertaking a site
audit to look at where the vulnerable surfaces are located and
where past graffiti attacks have occurred. Often these are readily
accessible flat surfaces where the graffiti will have most impact,
but this is not always the case and graffitists may scale walls
or bridges for example to give their work greater impact.
two sites are the same, no one set of protection measures will
be suitable for all situations. Each site must be looked at individually.
Typical site protection measures may include a combination of
- Floodlighting or improved lighting to illuminate
dark areas may act as a deterrent.
- Surveillance systems such as
closed circuit television may also help. In cities and towns around
the country, prominently placed cameras have been shown to reduce
anti-social behaviour of all types including graffiti.
patrols will also act as a deterrent to prevent recurring attacks.
However, the cost of this may be too high for most situations.
- Physical barriers such as a wall, railings, doors or gates can
be introduced to discourage unauthorised access to a vulnerable
site. However, consideration
has to be given to the impact measures have on the structure being
protected. In the worst cases, they can be almost as
damaging to the quality of the environment as the graffiti they
prevent. In others, they might simply provide a new surface for
- Soft and hard landscaping can form an important feature
of any anti-graffiti strategy. These features can be used to prevent
easy access and may include fastgrowing thorn bushes or large
- The location of new fixtures may affect an adjacent
structure. For instance the positioning of a bus shelter or telephone
box next to an ashlar stone wall may encourage graffiti, so alternative
locations should be considered.
graffiti on painted timber panelling
One of the
most significant problems associated with graffiti removal is
the need to remove it from surfaces that are repeatedly attacked.
Under these circumstances the repeated removal of graffiti using
even the most gentle methods will ultimately cause damage to the
There may be situations where the preventive
strategies mentioned above do not work or are not a viable proposition
at a given site.
Anti-graffiti coatings are usually applied by
brush or spray leaving a thin veneer that essentially serves to
isolate the graffiti from the surface. Removal of graffiti from
a surface that has been treated in this way is much easier, usually
using low-pressure water which reduces the possibility of damage.
Depending on the type of barrier selected it may be necessary
to reapply the coating after each graffiti removal exercise.
A range of
barriers is available, some of which are designed for more utilitarian
surfaces and others which may be more applicable to sensitive
surfaces such as masonry.
In the case of porous materials such
as natural stone there are several issues to be addressed before
selecting a barrier system:
- The coating should ideally be permeable
to water vapour, allowing the stone to behave as it would in its
- Ideally, there should not be any change in the appearance
of the treated surface. Many coatings cause a darkening of the
surface or sheen. The coating should perform in the same way in wet or
- The coating should remain stable as it ages and
should not discolour or be vulnerable to washing away through natural weathering
- The coating should be easy to remove from the surface.
Some coatings require hot, high-pressure water to remove them which
can damage a sensitive substrate.
- The coating should not be
toxic to people, animals or plant life.
- The process must be reversible
so that the coating can be completely removed should this be necessary.
Some coatings are permanent while others are designed to be washed
away each time any graffiti is applied. It should not produce
a cumulative adverse effect if repeated applications are necessary.
graffiti in a medieval chapel
Small trial applications should be made on a given surface before
committing to more extensive treatment. This would include applying
and removing the barrier
to check the ease of removal, as well as any adverse effects that
might result. This
will ensure that the product is suitable for the surface being protected.
on aqueous solutions produced from vegetable polysaccharides are
perhaps the most suitable for historic surfaces. Such barriers
are fully reversible and do not restrict the diffusion of water
through a porous substrate. Some slight colour change of the surface
is possible, but the effect is likely to be minimal.
There is no
prescription for dealing with every graffiti incident, but by
taking all the above into consideration a satisfactory strategy
can usually be adopted.
article is reproduced from The Building Conservation Directory, 2007
is Senior Conservator at Historic Scotland's Conservation
Centre in Edinburgh specialising in all aspects of stone
conservation. He heads a small team of conservators which
is responsible for the conservation of monuments and artefacts
throughout Scotland. He is a member of the National Committee
for Carved Stones in Scotland and also represents Historic
Scotland within the Anti-Graffiti Association. He is an
accredited member of the Institute for Conservation.
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