Ten Things You Need to Know
About Your Stained Glass Windows
These are some points useful for conservation of stained glass of all periods. The term
"stained glass" covers painted and/or stained glass as well as plain leaded windows,
copper-foiled glass, and other types of architectural glass.
1. How to clean a window
When called for, cleaning should always be undertaken in a localized, well-controlled
manner and with full consideration of the risks posed by the methods and materials
employed. The painted surface of a stained glass window can be very fragile. Any
cleaning should be undertaken by a professional. Close examination of the paint
condition is necessary to decide on an appropriate approach. If the condition is good then
gentle wiping with soft cotton rags and a mild detergent should be all that is required.
Soaking or poulticing (a moist mass of cloth) of a whole panel or an entire piece of glass
must be avoided.
2. Can I use tape?
Using tape of any kind on the painted surface, which is the interior surface, will damage
paint when removed. If tape is necessary to hold damaged or broken glass in place
always, if possible, tape from the outside of the window which is the side with no paint.
Or you can tape cloth or cardboard across a whole with tape to stop cold getting in.
3. All lead does not need to be replaced after 100 years.
Lead can last well beyond 100 years, in some cases much less. Regardless of its date, the
lead matrix is an integral part of the artistic design of a panel and contributes to its
historic value. Whether the lead needs to be replaced depends on a close examination of
the condition of the windows. Tell-tale signs of a window in need of releading include
bowing, buckling or sagging panels, tie wires loose from the structural support bars and
significant movement of the window when pressed. Even a window that is bowing may
not require releading if the movement happened a long time ago. It may still be strong. If
releading is required the lead should be replaced like with like i.e. the same profile and
width.
4. Documentation
When conservation is necessary the first step should include written and photographic
documentation of the current condition of the stained glass. A responsible restorer will
provide you with a written record of all the methods and materials used in a conservation
process.
5. Leaking windows.
Generally a window that is leaking and letting in water will require removal for
waterproofing. Tell-tale signs include rain stains on the stone at the base of the window
or drip marks removing paint on the window. Unless the window is removed from the
window frame, repairs for this type of problem are very difficult and usually only a
temporary solution. Recementing does not always necessitate releading. Once again
relead only after close examination of the condition of the windows (see above).
Removal presents the greatest risk to a stained glass window. If the stained glass is to be
removed it must be handled in a very specific manner. Only specially trained or
experienced persons should remove or handle panels.
6. Broken or missing glass
Depending on the nature and extent of the required treatment, and bearing in mind the
potential for damage during removal, conservation while the window is in place can be
considered as the first option. Losses, stopgaps, rearrangements, and later additions
provide evidence of the history of a stained-glass panel and should be documented where
possible. The insertion of replacements should only be undertaken when fully justifiable
such as when damaged glass is beyond saving. Any treatment must be guided by the
principles of minimal intervention and reversibility. Every addition of a new piece of
glass should be identified in a permanent manner with a date and signature or other
identifying symbols.
7. Vandalism
Save any glass that has been smashed out or fallen to the floor and place in an envelope
clearly labeled to indicate which window the glass came from. Any glass remaining is
invaluable to the conservator either for reuse or to replace.
8. Photograph your stained glass.
It is often the case that when a window is damaged or vandalized there is no photographic
record of the window to work from if a replacement is required. Photograph your
windows, professionally if possible.
9. Do my windows need protection?
The installation of protection is an important part of the preventive conservation of
architectural stained glass, which is vulnerable to both mechanical and environmental
damage. The principal aims of protection are to relieve the stained glass of its function as
a weather shield, to protect it against mechanical and atmospheric damage, and to prevent
condensation on the surface of the stained glass. Every window installation is unique, and
therefore the design of its protective glazing must take into account the particular
preservation needs of the stained glass and its architectural setting, as well as the physical
and aesthetic impact on the building. Knowledge about the functioning and effects of
protection are necessary to make the right decisions. Any external protection should
always be ventilated. Even if adding double glazing to reduce heat loss some form of
ventilation should be incorporated to prevent the introduction of a micro-climate between
the glass and protection. Wire guards can provide additional protection against
mechanical damage, although their potential visual impact must also be considered.
10. There is no “one size fits all” solution.
The conservation needs of your windows will vary, depending on many conditions,
including the age, size, location, and exposure to the elements of each window in your
building. Beware of the restorer who urges a single approach for all of your windows.
Each window’s condition must be evaluated separately. The choice of professionals
involved in the conservation process should be based on their education, their continuing
professional development and their experience, favoring quality over financial
considerations. The cheapest is not always the best, nor is the most expensive. It is a good
idea to call other churches for recommendations and to obtain several estimates.
The intrinsic value of stained glass is equivalent to that of any other work of art or
cultural heritage, therefore its conservation merits the same degree of attention and
professionalism regardless of its date or monetary worth. Do not be afraid to ask
questions. A good professional conservator will be more than happy to answer them.
Drew Anderson, Conservator in the Sherman Fairchild Center for Objects Conservation,
Metropolitan Museum of Art, New York
Tel: 212 396 5413
Email: drew.anderson@metmuseum.org
Drew Anderson has generously offered to evaluate competing bids for stained glass
restoration projects. Copies of treatment plans and cost estimates can be sent to him at
The Sherman Fairchild Center for Objects Conservation
The Metropolitan Museum of Art
1000 Fifth Avenue. New York, New York 10028
In order for Drew to offer an impartial opinion, NAMES OF FIRMS MUST BE
COMPLETELY BLACKED OUT or otherwise removed from all documents.