Interactions of Water with Paintings

ANDREA SANTACESARIA
Figure 2 Giorgio Vasari, The Last Supper: detail of a crossbeam
showing the trapezoidal section (dovetail) cut into
the thickness of the panel.
years of intense work by numerous restorers,
and returned to the Basilica of Santa Croce
in 2016. This is possibly the most important
intervention on a painted panel carried out by
the Opificio during its history and could never
have been accomplished without dedicated
teamwork (Bellucci et al. 2016).
History and construction of the
panel
Vasari created The Last Supper around 1546
for the Convento delle Murate, an order of
cloistered nuns in the district of Santa Croce
in Florence (Figure 1). Artists of that time in
Florence more typically painted scenes such as
this as frescoes directly onto the wall, but Vasari
chose to paint The Last Supper on five poplar
wood supports, side by side and mounted
inside a single large frame. It was therefore
possible for him to complete the painting in
his workshop and then quickly assemble it in
the cloistered convent, where male access was
prohibited. The work has impressive dimensions:
it measures 262 cm in height and 678.5
cm in width with an average panel thickness
of about 4 cm.
The construction of the five identical panels
generally follows the technique characteristic
of the 16th century: the boards were buttjoined
with three sturdy dowels (approx. 20 cm
long with a section of 18 mm) inserted along
each join After the boards had been glued,
these dowels were secured into tracks with two
wooden pins of about 6 mm diameter inserted
into the boards. As far as is known, this method
is unique to the construction of these wooden
supports, as usually the insertion of pins into
boards is specifically linked to the introduction
of wider internal elements than dowels, such
as wooden splines of a parallelepipedal shape.
The central join in the farthest right panel has
three wooden splines together with the three
dowels and is the only join that uses this double
system. The five panels are supported by crossbeams
inserted into the depth of the wood, as
was typical in 16th-century Florence (Figure
2).
The central panel has three crossbeams,
the others only two, placed at different heights
depending on the panels, probably because
although they were inserted into tracks cut into
the panels, they would have interfered with
each other had they been placed at the same
heights. The five panels also exhibit traces of
their original mode of connection and the
framing system for the whole work. On the
four edges of contact between the five scenes
there are perfectly coinciding dowel holes at
mid-height, suggesting the presence of pins or
dowels placed internally to connect the panels
and keep them aligned. On the upper edges
of the second, third and fourth panels (i.e. the
three central panels) there are evenly distributed
tracks: two in the central panel and one in
each of the two adjacent panels. These tracks
are regular, well squared and were presumably
used to hold four wooden inserts that connected
with the top edge of the frame. These
elements were most likely necessary to keep
the three central panels in position, preventing
them from tipping forwards and therefore
allowing the remaining two side panels,
which were aligned with the insertion of the
side dowels or pins, to be placed with sufficient
security.
A large rectangular backframe was probably
fitted on the wall destined to house the work,
its purpose initially to contain the painted
2

THE CONSERVATION LEGACY OF THE FLOOD OF 1966
Figure 3 Floodwaters invading Piazza del Duomo in November 1966.
panels and then to serve as anchorage for the
moulded profiles of the monumental frame.
The simple features described above would
have allowed the huge work to be assembled
safely, starting with the insertion of the central
panel from below at a slight angle in order to fit
the two wooden inserts in the tracks at the top,
and then bringing the painting vertical to rest
on the bottom plane of the backframe. The two
adjacent panels were then positioned by inserting
the pin or dowel at half height and making
the same movement to insert the wooden element
at the top of the track; finally, the lateral
panels were positioned and temporarily held in
place only by the central dowel. The whole set
of paintings was then secured by frame members
to hold the paintings in place safely.
From 1814 the work was held in the Basilica
of Santa Croce and often moved within the
building. It was initially placed in the Castellani
Chapel before being relocated to the Cenacolo
(the old dining room) where it can be seen in
a photograph from 1883. In 1966 it was located
in the street-level sixth room of the Santa Croce
Museum. Since the district of Santa Croce is
adjacent to the river Arno and is also located
in a slightly lower-lying area than the rest of the
city, all the rooms of the museum were at risk
in the event of the river overflowing.
The 1966 flood in Florence and the
damages to works of art
At dawn on 4 November 1966, the Arno burst
its banks and flooded a large part of the city
(Figure 3). One of the most affected areas of
Florence was indeed the district of Santa Croce,
where the waters invaded the Cenacolo and
other rooms of the museum in which various
paintings on panel were kept, including The
3

TATJANA WISCHNIOWSKI
Figure 2 Painting inside a metal ring filled with distilled water. (Photo: Tatjana Wischniowski.)
Figure 3 Excess oil floating on the water’s surface. (Photo: Tatjana Wischniowski.)
dedans) to prevent distracting light reflections
and then filled with distilled water (alternatively
rainwater or melted snow). With paint
made from pigments and poppy oil, the painting
is then carried out in several layers inside
the copper circle with the water. When one
layer is finished, the miniature is placed into
a box to dry, protected from dust. Every dried
ground and paint layer must be scraped flat
with a knife. The smoothness of the painting’s
surface is essential in the last step: the fixing of
the finished miniature under a glass.
Using a steel circle and distilled water the
replica of Lady in a Blue Striped Dress was
40

OIL-BASED PAINT UNDER A LAYER OF WATER: A RARE MINIATURE PAINTING TECHNIQUE FROM THE 18TH CENTURY
Figure 4 Finished replica painting under water. (Photo: Tatjana Wischniowski.)
Figure 5 Finished replica painting attached to a convex glass. (Photo: Tatjana Wischniowski.)
41

ALISON SEED AND SALLY HIGGS
Figure 2 Ernest Board, Latimer Preaching Before Edward VI at Paul’s Cross, 1548, 1910, 200 × 200 cm, WOA2591: photographed
before water damage. (Image courtesy of the Parliamentary Art Collection, reproduced with kind permission
of the Curator’s Office, Palace of Westminster).
describe case studies of mould-infected works
of art – pastels, watercolours and prints – but
no oil paintings. Unpublished student final
year projects at the Hamilton Kerr Institute
researched mould infestation on paintings
in the upper and lower galleries at Anglesey
Abbey (Teuma 2005; Woodhouse 2003).
More recently online blogs and papers have
discussed the occurrence and treatment of
mould on paintings. 1
Health and safety
It is clear that mould can be a serious health
concern. The NHS website 2 states that moulds
produce allergens, irritants and sometimes
toxic substances. Moulds can also cause
asthma attacks, and specific moulds cause diseases
such as histoplasmosis or aspergillosis.
Individuals with respiratory illness, diabetes
or suppressed immune systems are at higher
80

PAINTINGS AFFECTED BY MOULD AT THE PALACE OF WESTMINSTER
risk. Published guidance in the conservation
literature for the safe handling of mould and
its effect on health during conservation treatments
is limited (Guild and MacDonald 2004).
The health and safety risks of deinstalling
the affected paintings in a public space at the
Palace of Westminster were considered high,
particularly as the backs of the paintings could
not be assessed or the species of mould identified
until the paintings were removed. If the
fronts and backs of the paintings, as well as the
walls behind the them, were heavily affected
by mould, a surface area of 24 m 2 of mould
spores could be exposed during deinstallation.
According to levels of contamination in Guild
and MacDonald, this would be classified as an
extensive contamination (level 4 out of 4, >10
m 2 ) requiring full-face respirators (or a powered
air-purifying respirator with an HEPA filter),
disposable gloves and protective clothing with
head and boots covered, and organic vapour
cartridges for microbial volatile organic compounds
(Guild and MacDonald 2004: 19). To
minimise risks, deinstallation was planned on a
Sunday when the corridor would not be in use
by the public. An enclosed scaffold was erected
to contain the spores (Figure 3), an air scrubber
was used to filter particulates and full personal
protective equipment (PPE) was worn by those
involved in the deinstallation (Figure 4).
Mould identification
While there are over 100,000 species of mould,
different heritage objects from all over the
world have many fungal genera in common
and fungal species are rarely substrate specific.
Aspergillus is the most common genus found
in warm climates and Penicillium in temperate
climates. Penicillium cyclopium westling is
the species most commonly reported (Florian
2002: 24–5).
During deinstallation, and throughout the
project, microbiologist Sophie Downes took
swab samples from the surfaces of the paintings
and carried out air sampling. 3 Following
Figure 3 The East Corridor in the Palace of Westminster
showing the scaffold used during the deinstallation of
Henry VIII. (Image reproduced with kind permission of the
Curator’s Office, Palace of Westminster.)
an incubation period of one week she identified
Aspergillus versicolor on the front and
back of Henry VIII and on the wall behind the
painting. The mould on the front of the painting
was no longer viable (live), but was active
on the back of the panel and the wall. Viable
spores of Penicillium chrysogenum, Penicillium
brevicompactum, Penicillium commune and
Aspergillus versicolor were all found in very
large quantities on Latimer (Downes 2017).
None of these species of mould were listed on
the Health & Safety Executive’s list of known
hazardous species of mould (HSE 2013).
Treatment
During deinstallation it was found that Latimer
was still marouflaged to the wall, having not
been deinstalled since its original installation in
81