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12
BCD SPECIAL REPORT ON
HISTORIC CHURCHES
22
ND ANNUAL EDITION
early 19th-century stopgaps were filled
with pieces of unpainted coloured
glass, an honest repair which was easily
distinguished but visually very disturbing.
The most aesthetically destructive
aspect of the restoration was the use
of thick (10–12mm) leads throughout
the window, darkening the panels and
disguising the delicate relationship
between glass and lead achieved by
Thornton and his collaborators.
Exploratory conservation trials
undertaken by the York Glaziers Trust
(YGT) between 2005 and 2008 reviewed
a number of conservation options,
ranging from a light overall clean, to
the dismantling and full conservation
of the panels, with the recovery of John
Thornton’s cutline as one of several
objectives. However, one over-riding
priority was to install state-of-the-art
ventilated protective (isothermal) glazing.
In step with the guidelines of the
International Corpus Vitrearum (see
Recommended Reading), no dismantling,
reordering or restoration could be
justified without thorough research. As
a result, the forensic examination and
recording of every piece of glass has been
complemented throughout the project by
in-depth exploration of the antiquarian
and art historical context of the window.
The discovery of drawings and
photographs dating from the 1730s,
1880s and c1939 has been essential to
understanding the restoration history of
the window. Above all, the meticulous
description compiled in the 1690s by
antiquary James Torre has not only
shed light on individual panels, but has
confirmed the original panel order of this
immense biblical narrative.
After long and detailed consultation
with the Cathedral Fabric Commission for
England and other statutory consultees,
the Minster decided to proceed with
the dismantling, conservation and
reglazing of the window. This process was
supported throughout by the guidance of
Chapter’s East Window Advisory Group.
After careful cleaning to remove
hygroscopic dirt, the dismantled glass
pieces were closely examined for evidence
of their original location in the panel.
Clues provided by edges which had been
‘grozed’ by the medieval glaziers (nibbled
away with a hooked tool to fit snugly
into the lead) were always invaluable
evidence of authenticity and relationship
to adjoining pieces. Also, indications of
glass structure, corrosion patterns and
traces of lost paint, observable through a
binocular microscope, often confirmed
the evidence of surviving painted detail,
allowing multi-fractured and heavily
corroded pieces to be reunited. Mending
leads in obtrusive or lightly coloured areas
have been removed whenever possible.
The epoxy resins Araldite 2020 and Hxtal
NYL-1 have both been used for edge-
bonding, depending on the condition of
the glass and the nature of the fracture.
Detailed criteria have been used
to determine whether later stopgaps
should be retained or removed, and
those removed from the window have
been recorded and retained as part
of the project archive. Every process
and decision has been meticulously
recorded and new methods of digital
documentation have been developed
specifically for this project.
PROTECTIVE GLAZING
From the outset the East Window
Advisory Group was clear in its
view that the provision of protective
glazing was the single most important
contribution that modern conservation
could make to the preservation of John
Thornton’s medieval masterpiece.
In 1861 the Great East Window was
provided with crude exterior glazing, first
in the form of single sheets of glass and
later by diamond panes or ‘quarries’. Two
new glazing grooves were cut into the
window mullions of the main lights. The
exterior glazing was mortared into the
outer groove. The original glazing position
was abandoned and the stained glass
was set into the new inner groove. The
window was effectively double-glazed,
with no ventilation between the outer
and inner glazing. Advances in protective
glazing design have demonstrated the
importance of ventilation and this project
provided the opportunity to significantly
improve the system.
The new protection of the Great
East Window will take advantage of the
additional exterior glazing groove, but
the system is governed by the principles
of modern isothermal protective glazing
(see diagram opposite). An interspace of
Panel 5b following incorrect restoration by Dean Milner-White, who inserted
a second beast in the centre of the panel constructed from miscellaneous
fragments
The panel following conservation in 2013: ‘And they adored the beast, saying
‘Who is like to the beast? And who shall be able to fight against him?’
(Revelation 13: 4–6).