Issue 37 Spring 23 WEB - Flipbook - Page 15
The imposing neoclassical-style building was designed in
1937 by architect Albert Thomas, who also designed a
number of housing schemes for the St Pancras Borough
Council in the same neoclassical style, and was a former
assistant of EL Lutyens. The building, which is Grade II
listed, had an eight storey extension built in the 1970s and
a conservatory added to the roof in the 1990s. Over the
course of time the Town Hall, which is constructed of
Portland stone over a steel frame, has suffered from
weathering, dirt accumulation and Regent’s Street
disease; the corrosion of the underlying steel causing
damage to the stone.
In areas where the deposits were heavier, a natural bristle
or phosphor bronze bristle brush were used, or the area
was rubbed with a soft gritstone as appropriate. The
washing sequence commencing from the upper level,
working vertically so that the action of water run-off from
the immediate area of cleaning softens the soiling on the
level beneath.The DOFF system is very effective in removing stubborn dirt, many different paints and coatings
including some thermoplastic and bituminous mastic
materials. This steam and superheated water system is also
effective in removing chewing gum, grease, oil, algae
matter and killing off bacteria, as well as removing bird
droppings and other unwanted deposits, and kills off
spores negating the need for chemical biocide. This is a
cost effective, efficient method of cleaning that has no
negative environmental effects.
Following extensive surveys and a number of cleaning
samples, a substantial package of cleaning, repair and
restoration works was agreed. This included cleaning and
repair to the ornate interior marble and terrazzo flooring
and walls and the highly specialized repair of scagliola
plaster work. Externally, the cleaning works principally
involved the use of nebulous, Doff and Jos systems. The
exterior was heavily soiled and parts of the façade required
a combination of these techniques to remove the more
stubborn staining.
The system works on a variable combination of high
temperatures, which can reach up to 150°C, and pressure.
The operator can vary the temperature and the pressure
quickly and easily according to the type of material that
needs to be removed. Generally when the temperature is
high the water pressure on the surface being cleaned is
gentle and the volume of water low. This prevents the
material being cleaned becoming saturated and also keeps
the amount of water run off to a minimum. These systems
are easily portable units that come with a wide variety of
nozzles and lances that can be changed depending on the
requirement of the project.
Areas of the façade including the decorative composite
capitals were cleaned using one of the most traditional
methods, nebulous cleaning. This is a simple water clean
with a nebulous spray; the water pressure and type of
nozzles can be adjusted to suit the condition and fabric of
the building. The nozzles are specially designed to vaporise
the water creating a fine mist and are normally set on a
timer system to prevent over-saturating the building
material. The fine misty spray softens the deposits on the
building, which are then washed down using a Doff
system (low volume, medium pressure steam cleaning).
At Camden, in areas containing heavy or stubborn
staining the JOS method was necessary. This system was
developed to enable gentle, safe and effective cleaning of
historic buildings with their inherent problems, such as
delicate or friable surfaces. It works by creating a soft,
Above, Camden Town Hall after
Above, Camden Town Hall before
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Conservation & Heritage Journal
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