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| General Frequently Asked Quesions |
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1. How can we be sure that the vision we have for our new windows will turn out
the way we want it to?
You must insist on having the designs properly rendered on large printouts so
that you can see what they are going to look like and can formally approve them
in writing. You should also check that the company offering to do the work is
capable of delivering the quality you seek within the agreed budget.
2. What can we do about the damage to our beautiful old stained glass windows;
the glass has cracked and the glass painting has deteriorated?
You need to
commission a
studio
like
Bovard Studio that specializes in restoring valuable old stained glass art.
There are techniques for restoring all of the lost splendor to you windows and
also ways to preserve them so that
they
will l
ast for many generations to come.
3. How can we find out what can be done within our budget? We cannot even begin
to design the solution until we know what is possible.
You could hire expert consultants to help you. On the other hand you could find
an experienced stained glass studio (like Bovard) who are happy to spend
quality time with you on the project before they provide an estimate or
quotation. You will need to provide them with all the information you can as
well as with the solution you envisage. Their experts should be skilled at
drawing these things out of you so that they can provide you with a list of
alternatives.
4. What causes bulging?
As some stained glass windows age, the flat surface deflects, a condition that
is commonly referred to as bulging. This can be a symptom of significant
structural failure.
Lead has very little strength. If you hold a strip of lead came horizontally
out from your hand, it will fold over from gravity as it cannot hold its own
weight. This soft material lead makes a perfect glazing material because its
softness and flexibility protects the artistic stained glass while being a
strong enough matrix to hold the stained glass window together. The lead came
is not the only part of the structure of a stained glass window that holds it
up. A large stained glass window is constructed with panels of stained glass
that should approximate 12 sq. ft. or less in size. The flanges of the lead
came are packed with glazing cement in the space between the stained glass and
the lead came. This material not only weatherproofs the stained glass window
but also stiffens it, adding about 50% to the strength of a stained glass
window.
The panels are set into the mullions and muntins of the window's frame which
individually support each stained glass panel. Large stained glass windows are
made up of multiple stained glass panels. Steel reinforcing bars are placed
across the surface of the stained glass panels attached to the solder joints of
the stained glass window, as the solder joints are the strongest points in the
lead matrix holding the stained glass window together. The steel reinforcing
bars are attached into the surrounding window frame to hold the panel flat. The
steel reinforcing bars are designed to hold the stained glass panel in a
vertical plane keeping it flat and structurally sound.
As the stained glass window expands and contracts over time, the stained glass
panel can break away from its steel reinforcing system. The expansion and
contraction cycle also causes the glazing cement, a major structural as well as
weatherproofing component of the stained glass window, to loosen weakening the
window. As the stained glass panel weakens and breaks away from its steel
reinforcing system it begins to sag resulting in bulges. (Note: Some stained
glass window designs are more prone to bulging than others.)
Temperature changes are what cause expansion and contraction cycles in all
building materials including stained glass windows. Heat from solar gain is
trapped between unvented, improperly designed protective covering and the
stained glass window. Stained glass efficiently absorbs the sun's energy
causing solar gain to be trapped between the stained glass and protective
covering. This is a major cause of accelerated deterioration in stained glass
windows resulting in premature bulging in stained glass windows.
For example, one study conducted in Chicago in the 1990's of the heat buildup
from solar gain in the air space between the
stained
glass and
the protective covering measured temperatures of up to 150 degrees Fahrenheit
on a 20 degree January day in unvented protective covering. This is an example
of exaggerated expansion and contraction cycles which can result in premature
deflection (bulging) and structural failure of stained glass windows.
In the case of serious deflection of a stained glass window, the stained glass
will crack and eventually even pop out of the lead came.
5. Why does the protective covering currently on our windows discolor so
severely and rapidly?
The type of protective covering that this question refers to is polycarbonate.
The most common brand name is Lexan®. The yellowing is caused by ultraviolet
(UV) light. Lexan® is by far the strongest protective covering material
available. The surface is much softer than glass and wind blown dust can cause
microscopic scratching on the surface which, over time, causes the surface to
haze. The combination of yellowing and hazing results in severe discoloration
in simple polycarbonate. Most plastic protective covering placed on church
windows up through the 1980's was simple polycarbonate. Due to this problem,
General Electric, the maker of Lexan® brand polycarbonate developed Extended
Life Lexan® (Lexan XL-10) to resist yellowing and hazing. Extended Life Lexan®
has a coating of acrylic (a material that is significantly harder than
polycarbonate and also blocks UV light on its exterior surface). This greatly
reduces the yellowing and hazing problem for Lexan®.
When polycarbonate is selected as your protective covering material for its
strength in protecting your stained glass windows from vandalism or storm
damage, be sure Lexan XL-10 (Extended Life Lexan®) or equal is specified since
simple polycarbonate is still on the market for a few dollars less.
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