• Phone: 207.774.4154 Toll Free: 800.773.4154 Fax: 207.347.3302


As our stained glass treasures past through time impacts from environmental conditions, improper cleaning and daily activities can have adverse effects. If caught in early stages steps can be taken at a relatively minimal cost to correct or alleviate the issue(s). When left unchecked these effects can be devastating to the artwork. Please use this only for a reference to quickly check the status of your windows. If any of these factors are evident please contact a professional to properly evaluate your art.

Signs of deterioration, fatigue, stress and/or failure can include:

Buckling – When the “window” appears to bulge in or out of its original plane caused by factors like expansion, settling and freezing. Some movement is normal and may not continue. Any signs should be monitored for continuing movement can lead to major problems. Also known as bulging.

Window with serious “bulge”


Paint Deterioration – Painted Glass can be very susceptible to damage and decay caused by poor craftsmanship/techniques and moisture. There are two major forms of painted glass Vitreous paint – fired using a kiln to bond paints with glass and Cold paint – oils and enamels that are not fired. Vitreous paints when used correctly and without erosion stand the test of time. Cold Paints tend to be a much less permanent application and most often should be replaces with a fired technique.

Dedication on the left shows much less deterioration than on the right.


Oxidation – Leads and sometimes glass, especially painted, will corrode under certain circumstances. This corrosion is caused by chemical reactions on the surfaces from environmental conditions. Moisture and deposits – acid rain, pigeon droppings, incense/oil smoke – all lead to various forms of oxidation

Signs of heavy oxidation.


Broken Glass – Cracks or holes in individual pieces. Some cracks just add character and can be left as the are. Holes or missing glass usually require some form of repair.

Viewable Daylight – There should not be any light showing between the window and its sash or the lead and glass.

Lead deteriorated to the point Daylight is visible

These factors can lead to the above issues:

Thermal Expansion – Stained glass like all materials expand and contract when heated and cooled respectively. This is normal and should be accounted for in original design and installation. Lead’s coefficient of expansion is twice that of steel and 3 times that of glass. Windows become solar collectors and heat up during the day and cool at night. When the glazing (putty) between the lead and glass becomes dry and looses its elasticity the movement caused by expansion leads to crumbling of the putty which inhibits the window from contracting to its original position causing buckling and/or cracking.

Vandalism or accidental impact – usually broken pieces from stone or bb impacts are minimal but we have see major breakage from much larger objects

Poor Maintenance – Improper cleaning and/or poor past repair attempt can adversely affect a window. Make sure that the studio you choose to conduct maintenance or repairs has the knowledge and experience to properly care for your glass objects. Never use windex, harsh chemical or abrasive cleaners to wash your stained glass. Usually a soft, clean natural hair brush will clean loose dirt and polish leads. For areas of grime a soft cloth and warm water will get the job done.

Weatherproofing – Use of silicones or other sealers on windows to stop “leaks” has been a common “quick fix” – THIS IS NEVER APPROPRIATE! Sealers deteriorate and yellow over time and also dull the glass. It can also be very expensive to remove them from glass properly. If a window is leaking it is a sign that the window should be restored. Most commonly it is the sash or window frame that is leaking.

External Glazing (Storms) – Often plastic or glass and sometimes screen have been used to protect a window. When done correctly external glazing works well. If installed incorrectly the effect on a window can be devastating. If not vented glazing can increase thermal expansion exponentially

Comments are closed