Restoring An Original Tiffany Window
The restoration of any historic window is a great responsibility for both the window’s
trustee and the contractor. The owner or trustee of the stained glass window must
ensure that the restoration company has the training and experience to undertake
all necessary work in a professional manner. References should be provided (and
checked) and an extensive plan of action must be submitted by the contractor outlining
the full extent of restoration, including adherence to historic conservation procedures.
Comprehensive insurance must be engaged to safeguard against any perils that could
occur to the window during removal, rebuilding and re-installation or at the very
least the building’s current insurance coverage needs to be extended for off premises
When prestigious works by distinguished artists such as a L.C. Tiffany, J. LaFarge,
F.L. Wright or others needs to be restored, it may be advisable to engage the services
of a professional conservation consultant, specializing in stained glass restoration.
It is advisable to locate a consultant that is a member of a licensed architectural
firm. They will advise the trustee on the extent of work necessary and inform them
on specific technical requirements to ensure that irreversible restoration methods
are not undertaken. Historic restoration is definitely a job that is worth doing
right and should be entrusted only to those who have proven to be trustworthy.
The first step in restoring any historic stained glass window is to document its
current physical state and appearance. It is of the utmost importance to photograph
the stained glass window in both transmitted and reflected light prior to removing
it from its frame.
Take several photos of the window with transmitted light, (natural light passing
through the stained glass) without flash and being careful that the interior lighting
is extinguished. Since the exposure time will be longer (due to lower available
light) it is advisable to mount the camera on a tripod when taking photographs from
the interior side of the stained glass window.
Next make a record of the interior and exterior surfaces of the stained glass window
in reflected light (lighted from the same side as the camera). The sun’s light will
usually suffice for the exterior photos but a supplemental flash may be needed for
the interior surface photographs. Separate photos should be taken for each stained
glass panel (section) of the window, plus detailed photos of specific areas with
extensive damage such as cracked glass, missing areas of glass, badly damaged paint,
etc. Additional photographic documentation may be made back at the studio if required.
Prepare the windows for removal by securing loose and/or broken pieces of glass
with conservators tape. It is always advisable to secure the entire width and length
of the panel with tape, especially if the window’s structure is weak and fragile.
It is important to check any painted areas for stability prior to placing conservators
tape on these surfaces. If the glass paint is unstable or the stability of the paint
is in doubt, the painted side of the stained glass must not be taped. Once the panels
have been secured, they are carefully removed from the window frame and placed into
wooden packing crates with foam rubber sheeting to separate and protect the fragile
panels during transport. We pickup and deliver the panels in our own trucks.
Once back at the shop, the extracted stained glass windows are prepared for restoration.
The first panel is placed onto the glazing bench where more notes are taken and
more photographs made (if necessary). Then a rubbing is made for each section of
the window by placing vellum paper over the window and rubbing colored oil pastels
(or artists charcoal) over the lead lines to create a full size pattern of the lead
matrix. This pattern will be used later for reassembly. If the section contains
plating, as the Tiffany window in the illustration does, a separate rubbing is made
for each layer of plate. These additional plate rubbings are done on top of the
first rubbing using a different colored pastel for each successive layer of plating
(a rubbing is made after each plate layer is removed). This will show the fabricator
how each plate is "registered" on the window during reassembly. Notes are taken
of the size, profile and description of each lead came or copper foil area within
the stained glass window and this is recorded directly on the rubbing. Then two
copies of each rubbing are made one for reference and one as a working copy.
The restoration specialist must be sure that sufficient records have been made to
ensure an exact reconstruction can be achieved. Only then are the stained glass
panels carefully disassembled. The lead came is cut away and one glass piece at
a time is removed and placed in it’s correct location on the working copy of the
rubbing. During disassembly it is important to keep a sample of each different lead
came size and profile or a section of the copperfoil assembly for reference and
When the entire panel has been disassembled it must be cleaned and inspected. Each
piece of non-painted glass is cleaned with Triton X-100, a professional quality,
non-ionic detergent (made by City Chemical Company of NY) or an equivalent pH neutral
glass cleaner mixed with distilled water. Prior to cleaning, painted areas of the
window must be tested to determine that the paint is stable. If it is, these areas
should be gently cleaned with a soft cotton cloth and distilled water. Unstable
painted areas need be stabilized. The basic treatment is to coat the painted surface
with a restoration grade clear fixative to bond the remaining paint to the glass.
However, it is intensely important that the fixative used be chemically compatible
with the underlying paint to ensure no further damage is induced. For this reason
it is necessary to consult an expert restoration specialist to determine the appropriate
consolidation method for the particular problem encountered. Areas where the paint
is badly faded, has been washed away, or otherwise lost, should be restored by first
treating the existing paint with the clear fixative. Then the missing details are
painted onto a new piece of 1/16" (1.5 mm) or thinner clear glass that is plated
over the original painted stained glass. This ensures the historic work remains
unaltered and undisturbed and makes the restoration fully reversible in the future.
Cracked and broken pieces of stained glass are repaired by edge gluing with clear
Hxtel epoxy (a commercial brand product), clear silicone, or by copper foiling
and soldering the pieces together. The specific repair method will be decided based
upon what is best for the historic preservation of the particular stained glass
Missing pieces of art glass can sometimes be closely matched from the more than
4,000 colors, densities and textures that are manufactured and available today.
If a close match cannot be found from available glass, you can plate two layers
of stained glass together to produce a third color and texture. If necessary several
plates can be combined to give the stained glass restoration artist countless possibilities.
In some cases where a glass making formula is known, a glass manufacturer may be
willing to custom create a particular stained glass sheet to match a destroyed original
piece. This is an expensive alternative but if the missing glass is dominant in
the design or if the window is an exceptional work, this may be the best solution.
The various sizes and profiles of lead came also need to be closely matched. Many
of the came profiles are available as standard stock items manufactured from existing
dies, however other more specialized shapes may need to be specially ordered from
custom or rarely used dies and depending on the importance of the window, may be
a necessary step. Other cames are hand made for a perfect match.
Once all the glass has been cleaned, broken pieces repaired, missing pieces replaced,
painted pieces replicated, and all other materials are obtained, the stained glass
window is ready to be reassembled. The pieces will be placed on the working copy
of the rubbing, precisely as the window was originally created. The fabrication
will be carried out by skilled craftsmen in essentially the same tried and true
method as the window was fabricated decades before.
The Tiffany window we are restoring here has complex plated sections that will require
the fabricator to devise an assembly of lead cames to create a shape otherwise not
available. They will solder several strips and/or layers of came together to create
a shape based on the sample saved during disassembly. We have found that a modern
improvement can be made to the original structure of plated sections by applying
a silicone seal around the edges of the stacked plates of glass. This will prevent
dirt and water from collecting between the plates, which cannot be cleaned without
disassembling the window. Contamination of plated sections is a major problem encountered
in historic windows that include extensive plating.
Any structural deficiencies in the original windows should be addressed to prevent
the premature failure of the window in the future. One major structural remedy is
to use lead came that has sufficient tensile strength. It is crucial to use a lead
came manufactured by the extrusion process using a lead alloy that contains antimony,
silver, copper, or tin. The original stained glass window was probably fabricated
using pure milled lead (without alloy additives) which is comparatively soft and
malleable (lead alloy came is a recent development). This improvement alone will
greatly increase the expected longevity of the stained glass restoration. Another
common structural deficiency is the use of a single layer of relatively thin glass,
usually 1/8” (3 mm), in the borders. This fragile border is required to support
the heavy weight of the central glass section and is particularly troublesome in
windows with multiple plates of glass which add considerable weight. Unfortunately,
this situation often results in the folding and sometimes total collapse of the
border, especially at the base and lower sides of the window. A simple, reversible,
non-invasive remedy for this deficiency is to apply a second plate of clear glass
to the border areas on the exterior side of the window, thereby doubling the strength
of the borders.
When fabrication is complete, the window must be cemented with a glazing cement
specifically formulated for leaded windows. The cementing process packs the space
between the flanges of the lead came and the stained glass with a sealant to stiffen
and strengthen the window as well as weatherproof it. Most cement compounds have
a black dye component to enhance the surface the new "silvery colored" lead with
a dark, richly colored patina to give it a more mature appearance.
During a restoration such as this Tiffany window, we take special notice of areas
with the most structural damage. These areas of distress may be due to an insufficient
supporting structure or to weaknesses within the windows design.Whatever the reason
it is our responsibility to correct the problem in the least intrusive way. Obviously
these areas require additional structural engineering and one of the most effective
solutions is to attach brass rebar directly to the lead in the structurally deficient
areas of the window. This rebar is a flat brass rod, 1/16" (1.5 mm) thick and anywhere
from 1/4" to 1" (6.3 to 25.4 mm) wide. It is soldered directly to the lead came,
perpendicular (90°) to the face, on the exterior side of the window. Preferably
these rebars should be kept as straight as possible but they may be bent to follow
along the length of a gently curving lead line. This technique structurally reinforces
the stained glass window with minimum aesthetic impact. (see example on
While the stained glass window is "in the shop" undergoing restoration, it’s an
opportune time to take up the necessary repairs and restoration to the window’s
frame. In some extreme cases the frame may need to be totally replaced, at the very
least it should be cleaned, sealed and refinished. If the window restoration company
does not provide these services, a qualified carpenter should be called to make
an assessment of the frame’s integrity and complete the repairs.
The culmination of any restoration is the time of reinstallation, when the restored
window is returned to its rightful home. A scrupulously restored window, with structural
weaknesses remedied and installed with a properly vented protective covering (see
this page), can be expected to last significantly
longer than the original stained glass window, before it will require another restoration.
It is a very gratifying experience to return a Tiffany or other historic stained
glass window to its original appearance and condition. It is rewarding to witness
the dramatic contrast between the dirty, deteriorated, misshapen window of the past
to the richness of color and structural integrity of the restored installation.
It is a thrill to return the many lost details of a window, details that seemed
to be hidden in the past and are now mysteriously resurrected into the living present.