BCD SPECIAL REPORT ON
HISTORIC CHURCHES
21ST ANNUAL EDITION
21
worn, although there were also areas where
porosity in the original casting had allowed
material from the core to leach through to
the surface. In several places there were large
encrustations of salts and corrosion products
forming a distinct disfiguring layer, with
further corrosion continuing underneath.
There were also problems where the
separately cast components of the piece
had been joined. In places, the sections
had been brazed in with copper, which
was an entirely different colour, and there
were areas where pieces of metal appeared
to have been hammered in to fill gaps.
Water entering the sculpture through the
original casting joints and through corrosion
holes presented a problem for the room
beneath, where the book of remembrance
is displayed. The book was removed to be
digitally recorded, conserved and temporarily
displayed at the University of Manchester.
In addition to working on the repair and re-
instatement of the page-turning mechanism,
conservators at the university also had to
consider adding new pages to commemorate
those killed in more recent conflicts.
CLEANING
The removal of the book of remembrance
in early May 2013 allowed Eura’s staff to
begin the process of testing appropriate
cleaning techniques. It was decided to
select a small area of horizontal surface not
visible from the ground and closely examine
the lacquer to determine its condition
before carrying out cleaning trials on it.
A lightweight scaffolding tower was used
to gain access to the base of the bronze and
an area on the south west corner was chosen
for the trials. Micro-photos were taken of
the selected area before and after testing to
enable precise recording and assessment of
each treatment. The area was then cleaned
using a one per cent solution of Triton
X-100 non-ionic detergent, agitating with
natural bristle brushes. The surface was
swab-dried, rinsed with de-ionised water
and allowed to dry. To the naked eye there
was no apparent difference between the
trial area and the surrounding metalwork,
although it could be seen from the swabs
that some soiling had been removed.
It was clear from the micro-photographs
that the lacquer was thicker in some places
than others, that the colour varied considerably
and that green corrosion products were visible
in many places. Examination of the surface
also showed that the sculpture was greener
where the lacquer was more severely degraded.
Once the trials had been completed the
results were disseminated to all interested
parties, including WMT and English Heritage,
to allow for discussion of the best way forward.
As the lacquer coating was clearly failing
it was necessary to remove it, a conclusion
supported by English Heritage’s consultant.
Further trials were carried out and
the best results were obtained with a
dichloromethane-based solvent. The use of
dichloromethane has been heavily restricted
under EU REACH (Registration, Evaluation,
Authorisation and restriction of Chemicals)
regulations since 2012. However, its use
is sometimes necessary when removing
historic treatments which weren’t applied
with reversibility in mind and, if used
carefully by conservators, it can safely remove
coatings without damaging the substrate.
The memorial was completely scaffolded
and screened for access and safety reasons.
Further protection was added by laying a
geotextile membrane (a permeable synthetic
fabric) over surfaces to collect residues and
to protect the local drains from the run-
off of cleaning products and old lacquer.
The dichloromethane was applied with
soft bristle brushes and swabbed off, and the
bronze was thoroughly cleaned between coats
with a high pressure steam cleaner, taking
care not to damage any existing patina. Even
with this treatment it took up to five coats in
some areas to fully remove lacquer residues
from sheltered crevices. All chemical residues
were caught in the geotextile membrane
and removed from site for safe disposal.
The removal of the lacquer coating
allowed for further assessment of the
surface and a photographic reference
was made of problem areas.
While some loose corrosion products
were effectively removed by repeated steam/
pressure washing, there were still areas of
active corrosion, intractably stubborn salts
and black sulphide accretions to deal with.
Working closely with WMT and the other
organisations concerned, it was agreed that
the worst areas of active corrosion should
be selectively and carefully cleaned further
using the wet Jos method. Jos is essentially
an air/water abrasive cleaning system which
is suitable for removing active corrosion
from bronze. In this case the medium used
was marble dust (calcium carbonate) mixed
with water and applied under pressure.
On bronze statuary, great care must
always be taken by the operatives when using
an abrasive system like Jos as it is possible
to damage the surface of the bronze. For
this reason, only a select group of well-
experienced operatives and technicians
was allowed to undertake the process. In
addition, it was used as lightly as possible
and only in those areas where it was
absolutely necessary, with a small nozzle
fitted to confine the spread of the medium.
Nevertheless, at the end of this process
there still remained, in places, very thick
coatings of salts or black sulphide deposits
despite water/steam pressure of up to 80
bar and selective Jos treatment. So, the final
stage in the process was the careful removal
of these deposits by hand, using wooden
spatulas, bronze spatulas and dental picks.
The whole sculpture was again
fully washed and steamed before
patination trials were commenced.
SURFACE REPAIRS AND PATINATION
Large holes and cracks in the surface of
the sculpture were repaired with bronze
mesh solidified with bronze-loaded resin.
Smaller areas were filled with bronze-
loaded resin or, wherever possible, with
coloured microcrystalline wax.
Salts and other material which had leached from
the core of the bronze formed thick encrustations in
some areas.
Salt accretions with active corrosion (the green areas)
and a band of black sulphide staining
Poorly sealed gaps at the feet of the topmost soldier
where the castings had been joined together
Staining and pitting around a large, active corrosion
hole which had penetrated to the core of the rifle butt
