Charles Tuttle Stained Glass

Frequently Asked Questions

What is a stained glass window?

Stained 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.

How long does a typical stained glass window last?

The 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.

What causes a stained glass window to fail?

Window 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.

Human intervention can also hasten the deterioration of a stained glass window assembly.

Improperly 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 window’s life expectancy from seven or more decades to just a few years.

Will my window loose value if it is disassembled, or if the lead or the frame is replaced?

The 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.

How do I know if my window is worth restoring?

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.

“Value has two definitions: market based and intrinsic.”

Unless 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 window’s 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.

How 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

Stained Glass - Boston

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