73Listed Heritage Magazine July/August 201172 Listed Heritage Magazine July/August 2011
LEADED LIGHT WINDOWS LEADED LIGHT WINDOWS
The Care and Repair ofLeaded Light Windows
they can be repaired should be of
use to anyone involved with historic
buildings glazed in this way.
Leaded lights are very simply
built. The origins of combining the
H-section lead (known as “cames”)
with glass came about due to glass
production techniques only allowing
small sections of glass to be made.
Combining the two materials meant
that bigger spaces could be glazed.
In many ways, the limits of early
glass production led to the creation
of the stained glass industry as many
of the worlds finest stained glass
windows would never have been
produced if the leading of glass had
not been invented. Fortunately for
historic home owners, painted and
stained glass is quite rare in all but
the grandest of historic houses.
New leaded lights have an average
life expectancy of around a century.
In the right conditions, leaded glass
has lasted several hundred years and
thanks to more widely available
expert conservation work, there is
still a surprising amount of medieval
leaded glass still extant today,
principally in our church buildings.
However, most leaded glass fails
long before this and there are a
number of signs of failure that you
can look for.
Firstly, examine the leadwork.
In its best state, each lead came
should be flat, smooth and straight
at the edges and the panel as a
whole should be the same. One of
the first signs of a problem is almost
always presented in movement in
the leadwork as a whole or in
individual cames. Individually, the
lead cames can disfigure by
becoming furrowed at the edges,
raised, bowed or otherwise
misshaped thanks to years of
expansion and contraction. At the
same time, the entire lead matrix
can move as one, taking the glass
with it and leaving the entire panel
buckled and bellied inwards or
outwards. Some movement is all
part of the charm of older leaded
light windows and minor movement
is not in itself a major cause for
Nantclwyd House,Ruthin, NorthWales, a textbookexample ofproperly restoredleaded lightglazing.
concern. However, where this
movement is more pronounced
there is a danger of the force of the
movement causing the glass to break
resulting in the unnecessary loss of
original historic fabric. Movement
in the lead work also breaks up the
cement which binds the glass and
lead together, leading to ingress of
weather. In severe cases, the same
movement can cause the soldered
joints in the leadwork to break apart
leaving the whole panel structurally
insecure.
The second thing to look at is
the glass itself. Despite its inherent
predilection for breakage, the glass
is the least likely part of the window
to fail of its own accord. Old glass
is full of natural imperfections,
sometimes so severe that actually
seeing through it is very difficult.
At the same time, it is these
imperfections that make leaded light
glazing really glitter and come to
life. In most cases, it is quite possible
to save original old glass from
dilapidated lead cames. In our studioÊ
Metal framecorrosion causingdamage to leadedlight glazing.
Leaded glass is the oldest
glazing technique still in
production today and is
widely used across the world. As
a method of glazing and as an
artistic medium, leaded glass is both
extremely versatile at the same time
as being functional and durable.
Given the right conditions leaded
glass can and does last for hundreds
of years meaning that there is a
great deal of very old glass
remaining in many older properties,
often unnoticed and at times
underappreciated.
Owners of historic buildings are
usually lovers of historic buildings,
but with that appreciation comes
a level of responsibility, as well as
seemingly endless invoices and
repair bills. Special buildings call for
specialist craftsmen and women but
drawing upon their knowledge,
training and experience inevitably
costs money. It is for this reason that
the issue of maintenance is so high
on the agenda for people caring for
such buildings. Anyone who has
taken note of SPAB’s National
Maintenance Week each year (see
www.maintainyourbuilding.org.uk)
or examined the costs of regular
maintenance versus large-scale
programmes of restoration will be
fully aware of the financial
implications of ignoring day to
day upkeep.
Keeping up with the maintenance
doesn’t mean that your property has
to become a money pit. Most
maintenance is simple – clear the
gutters, unblock the drains, replace
slipped slates. Other maintenance
issues are less straight forward, but
with a little knowledge of the subject
you can still stay on top of most
things. Leaded light windows are
one of these things and the
following examination of the
materials used, the way in which
they are built and the way in which
74 Listed Heritage Magazine July/August 2011 75Listed Heritage Magazine July/August 2011
LEADED LIGHT WINDOWSLEADED LIGHT WINDOWS
Above:Fully repairedframes and leadedlights.
Middle top: A severelycorroded saddlebar causingdamage to glass,lead and masonry.
Middle Bottom:Metal framecorrosion causingdamage to leadedlight glazing.
experience, it is very rare that we
have to replace such glass, even if
only a few panes or “quarrels” of
the original glass remain. Keeping
original fabric which still has life left
in it, even if it is as small and
seemingly insignificant as a single
quarrel of glass, is important in
maintaining the integrity of the
building as a whole, so it is always
good practice to retain the old glass.
Similarly, leadwork should not
automatically be deemed to be
sacrificial as in certain cases it too
can be repaired and retained.
Caring for the glass in leaded
panels is quite straight forward.
Day to day cleaning inside and out
should normally be carried out using
cotton wool and de-ionised water.
Older glass and modern mouth
blown glass is very susceptible to
scratches, so take off rings and
jewellery before cleaning. Don’t
scrub, clean lightly and often, never
use cleaning agents or abrasive
cloths as both can damage the
cement which holds the lead and
the glass together. If in doubt, call
any leaded light maker or restorer
for help. Never clean painted or
stained glass yourself – this should
only be carried out by a specialist
as such operations can present a
minefield of problems.
Next, look at the more functional
parts of the panel. Most leaded
lights are held in place with ties.
These are usually flat or round
sections of wire in lead or copper.
The ties are soldered to the panel
at joints in a straight line across the
panel and attached to a metal tie bar
or saddle bar which is lodged into
the frame or aperture at each end.
The bars can run in almost any
direction along joint lines, either
in straight runs or wrought around
more unusually shaped leadwork.
Lead ties are normally folded
around the bars and copper ties
usually wrapped around and then
twisted and folded at the ends. It
is these ties that give a leaded light
panel most of their structural
strength against wind, bird impact
or draw from opening doors for
example. As part of any
maintenance monitoring, it is always
a good idea to check that the ties
are attached to both the panel and
the tie bar. The force of moving lead
as outlined above can often cause
the ties to detach leaving the panel
unsupported. A good example of
such failure was seen at Chester
Cathedral in 2008 when clerestory
leaded lights were torn inwards by
the pressure draw caused when
opening a pair of large doors.
Finally, check your frames.
Leaded lights can be glazed into
almost any type of frame, or directly
into masonry apertures as seen in
most church buildings. Significant
For more information please call:
01244 906002 or visit:www.recclesia.com
movement to any aperture can spell
disaster for leaded lights, although
they are by their very nature more
capable of coping with minor
movement better than plain glazing.
One of the biggest problems we
come across at the studio is the
effects of corroded metal frames on
leaded light glazing. It is widely
known that metal expands when
corroding, meaning that the leaded
light glazing is forced increasingly
tightly into the frame over time.
Eventually, something has to give
and the pressure usually gets to the
glass first, exerting enough force
on it to smash it.
Similarly, where timber has
swollen or masonry moved or
delaminated, the stress upon the
glazing can be immense, causing
cracks and even wholesale shattering
of sections of glass. Identifying these
issues is again quite easy and some
simple steps such as keeping metal
and timber frames well decorated
can be money or time well spent
if it saves a much larger glazing bill.
It is also a good idea to check metal
frames for sitting water, either as a
result of weather or condensation,
something which if gathering to
excess is also in itself damaging
to leaded panels. Many metal
casement windows will have small
weep holes along their base to allow
release of sitting water so make sure
that they are not blocked with years
of paint or bundles of dead insects.
With the right level of care,
leaded light windows can serve any
property well and will outlast most
of us by quite some margin. Good
practice in the repair of leaded lights
will always involve the retention
of as much of the original glass as
possible and in some cases retention
of very old leadwork. Cleaning is
straight forward and maintenance
checks very simple. When you do
Garth Evans and Kat Waltoncompleting re-leading of originalglass into new lead cames.
identify an issue such as those
outlined above, there are plenty
of traditional craftsmen and women
in the UK who are highly skilled
and capable of repair and restoration
work, a number of whom are listed
in the directory at the back of this
issue.
Jamie Moore oversees a team
of highly skilled craftsmen and
women at Recclesia Ltd, specialising
in the conservation and repair of
historic buildings with in-house
traditional skills including
stonemasonry, lime mortars,
metalwork and stained and leaded
glass.