Choose Wisely Among Stained Glass Restoration Methods
By B. Gunar Gruenke, President of Conrad Schmitt Studios
Published in "Church Executive" Magazine
Few things are as distressing as the realization that an artistic treasure is in jeopardy. Unfortunately for buildings with stained glass windows 50 or more years old, this discovery is commonplace. Adding insult to injury is the fact that recommendations for stained glass restoration are often conflicting.
Methods of restoration
Much of the debate centers around the value of restoring-in-place versus full conservation or restoration methods. Restoring-in-place involves attempting to return sagging windows to their original, upright position by patching and ironing the leading and then reinforcing them. This is a bandage approach, which does not solve the problem of uneven stress throughout the window. On the contrary, attempting to push the lead back into place creates new points of pressure on the glass.
Conservation and restoration, on the other hand, call for removing the windows, dismantling them completely, and replacing the stretched and aged lead rods with new ones. This rebuilding of the window structure provides the window's matrix with the most even distribution of weight - therefore the least stress - possible. On the surface, restoring-in-place has appeal because it is less costly, and it does not always require removal of the windows. However, restoring-in-place is a temporary solution that continues to risk the essential structure of the window. And it costs a substantial portion of what full restoration would cost.
One Midwestern church hired a company to "stabilize" its windows 15 years ago. They spent $40,000 for the scaffold, labor and materials. Now an examination of the windows reveals bulging, lead molecular breakdown, putty failure and cracks at the solder joints. The windows are begging to be completely removed, dismantled and re-leaded. The quote for this is $150,000. The fully conserved or restored windows are likely to last for 100 years.
Lead replacement is key
To adequately understand the problem with aged lead caming, one must consider the inherent nature of the material. Lead is pliable and malleable, but it does not have a memory, nor can it be reduced in size once stretched. As an example, take a 4-inch piece of lead and stretch it to 5 inches. Now attempt to push that lead back down to 4 inches. What will happen is that the lead will bow out to one side or the other. With stained glass on both sides of the lead caming in a window, the additional pressure will unfortunately be absorbed by the glass, which is likely to crack to release the tension.
In most cases it is in the best interest of stained glass windows with decayed lead to fully re-lead them. If the budget does not allow for the entire project, then the worst windows can be done first (usually southern exposure), followed by the others in phases. In addition, the frames should be repaired and repainted and the storm glass should be cleaned and resealed with each window re-leading. If the storm glass is lexan, polycarbonate or plexiglass, it should be replaced using plate glass or safety laminate. It is also essential that any storm glass be vented to release the build-up of heat and condensation between the stained glass and the protective glazing.
Quite apart from the structural considerations is the aesthetic improvement to be gained from re-leading. While lead repair can lead to a mottled lead appearance, new lead provides an almost lyrical beauty. Benefactors of stained glass restoration find it rewarding to see the renewal so apparent, as the lead shines with strength, beauty and the promise of longevity.
Choose Wisely Among Stained Glass Restoration Methods (PDF 1.38 Mb)