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.