is a stained glass window?
glass windows are comprised of a mosaic matrix of colored glass
held in place by lead came and surrounded by a wooden or metal
frame. Lead came consists of pure lead, extruded into a form
that, in profile, resembles an I-beam. The glass sits into the
groove of the I-beam channel; it is surrounded on all sides
by the lead came; the glass is further bonded to the lead by
special glazing putty, called cement. Glass, cement, and window
frame combine to create a remarkably strong, monolithic structure,
capable of lasting 100 years.
long does a typical stained glass window last?
life expectancy of a stained glass window is about 75 to 100
years; that time can be significantly shortened by exposure
to the elements, or human intervention. Even well intentioned
intervention can have its negative impacts.
causes a stained glass window to fail?
failure is usually due to heat and oxidation. Heat causes the
window elements to expand and contract. These elements: lead,
glass, cement, and window frame, expand and contract, often
divergently from one another. This provides an opportunity for
moisture to penetrate the window elements and their respective
interfaces. Moisture dissolves and leaches the lead from its
matrix; moisture replaces the oils that make cement strong,
yet flexible; and rots and rusts window frames. The one-time
monolith begins to return to its individual components, the
window looses it structural integrity, and eventually becomes
incapable of supporting its own weight.
intervention can also hasten the deterioration of a stained
glass window assembly.
installed storm windows or other protective glazing can trap
moisture and increase the temperature of space between the stained
glass and the storm window by as much as 800 degrees. Such humidity
and temperature extremes act as a catalyst to the natural forces
reducing the windows life expectancy from seven
or more decades to just a few years.
my window loose value if it is disassembled, or if the lead
or the frame is replaced?
real fabric of a stained glass window is the glass itself. All
else is there to support the glass canvas and is completely
replaceable. Therefore, any improvements to the supporting material
could only serve to improve the value of the piece.
do I know if my window is worth restoring?
a window to its former self is more time consuming than building
new. It requires extensive mapping and recording of the existing
structure and of the interrelationships of glass, lead, reinforcing
bar, and frame; it also requires painstaking patience and great
skill in disassembling each individual piece without damaging
the glass fabric. And for those windows with missing pieces,
finding a near perfect match to 100-year old glass may involve
searching four countries on two continents.
has two definitions: market based and intrinsic.
you have a signed piece, it may be difficult to say what the
market value may be. If you know the age of your house and its
construction history, you can make an assessment of the windows
age, but age alone does not equal value. It may come down to
how you feel about the piece. As in any art form, the true value
of art is what the owner places on it.
can I tell if my window needs restoration?
- Bowing: most windows are
constructed flat. Any significant bowing stresses the glass
and will fracture the glass in time.
- Cracked or missing glass:
especially in bowed areas
- Gaps between lead and
glass: weak areas that could lead to bowing or glass falling
out of the matrix
- Broken wire-ties
(pigtails): The window surface is no longer connected to the
reinforcing bars - this will most certainly lead to bowing
- Detached reinforcing
bar: re-bar must be secured to the surrounding window frame.
Detached or floating bars are not supporting the
weight of the window, which will lead to significant structural
damage. Windows larger than 20x20 inches generally require
support older window construction used reinforcing
bars connected by wires and soldered to lead came at key points
throughout the window, or in some cases, the rebar was soldered
directly to lead came
- Soft flexible surface:
stained glass surfaces should feel rigid to the touch; akin
to a similarly sized single pane of glass