Issue 47 JUNE - Flipbook - Page 57
With these water-based systems a good surface clean can
be achieved, but key areas of concern include high usage
rates of palatable water, over-saturation which can mobilise salts within the façade causing corrosion of metal
fixings and efflorescence, the risk of frost-damage during
the colder months (which can lead of to intricate carvings
cracking and braking). With the constant water misting
systems unsightly, time-consuming, and expensive scaffolding will be required, more persistent staining will require scrubbing or mechanical removal, can cause
staining on limestone/sandstone, creates conditions
favourable for rot in timber structures, and is ineffective
on tightly bonded soiling.
Above, Somerset House before
Below, Somerset House after
Dry cleaning methods
There are two key types of dry-cleaning methods, abrasive
cleaning and façade gommage cleaning. With abrasive
cleaning methods a medium to high pressure is used with
an abrasive medium such as sand, shot, or ground-up nut
shells to chip away at the surface of the dirt and grime.
With this type of cleaning a good surface clean can be
achieved but it can cause damage to the façade’s surface
especially on softer stones such as sandstones and
limestone, repeated use can, over time, cause highly
decorative and intricate areas to be damaged or worn
away by this method.
With the façade gommage cleaning method, ultra-fine
Aluminium silicate powder is blown under low pressure
over the surface of the façade, gently rubbing away the
surface dirt and grime. Unlike most wet and dry options,
scaffolding isn’t required so reducing the time taken to
perform the clean and no temporary structures obscuring
the building (an ideal choice for hotels and retail businesses). The system also offers one of the best end results,
taking a building back to the original façade colour while
preserving any patina which may be present.
Chemical and spot surface cleaning methods
When smaller more specific areas need cleaning, such as
graffiti removal or more stubborn or encrusted stains the
use of specific cleaning methods such as chemical treatments, which are more commonly used for paint and
marker graffiti on the sides of buildings. These need to be
patch tested to ensure that no reaction to any of the materials on the façade.
Above, facade cleaning Reform Club,104 Pall-Mall, London.
Poultice application can also be used, but once again only
on small areas after patch testing has been carried out.
These topical pastes are applied and left to remove stains,
but with typical ‘dwell’ periods of 24 to 72 hours, these
are slow and may require additional applications for them
to be effective.
Lazer and cryogenic cleaning methods use ablation as a
way of removing encrusted dirt and grime. Once again
this is not suitable for larger areas of soiling.
Above, Apex Hotel after
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