Posted on behalf of glass conservator, Ariana Makau:
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Dear Stacy,
Thank you for forwarding this inquiry.
At Nzilani Glass Conservation, we document every single lead, zinc or brass came (measuring them with calipers) that are part of the windows we conserve. Although the majority of pieces we work on are from the 20th century, we recently worked on a piece from the 16th century. A lot of valuable information can be lost if this step isn't taken. I've attached an image of a chart we made for ONE window we are currently working on for Grace Cathedral (https://www.dropbox.com/s/2gj96c1kbpuauec/IMG_0601.jpg?dl=0).
It is imperative to document the profiles to accurately reglaze portions or the entire window. The "arms" referenced in some of the HistArch discourse are called flanges and affect the aesthetic presentation of the window. Changing their profile will change the visual reference between the windows and the surrounding architectural framework. In addition, if thicker leads are replaced with thinner leads, the structure of the overall windows may be compromised, even if it is a few millimeters.
Most important is the "heart" of the lead (the center section that isn't viewed unless part of the panel is taken apart). Two measurements are important.
First, if the heart height is too short, it won't allow space for the putty to encompass the glass and weatherproof/seal/support the window. If it is too high, the putty may fall out over time and again the structural integrity is compromised.
Second, and most important, is the width of the heart. This generally varies from 1/32 - 1/8. If this isn't accurately measured at the onset and replaced with the same profile (height, flange and heart) replicated, even the most skilled glazier can't replicate the original dimensions of a window with the original glass. It will either end up too small or too big, thus affecting a successful installation.
I'd welcome further inquiries about this subject. I can be emailed directly at: [log in to unmask]
-Ariana Makau
Ariana Makau | President & Principal Conservator
AIC Professional Associate
@nzilani_glass
www.nzilani.com
NZILANI GLASS CONSERVATION, INC. -"Be Safe. Have Fun. Do Excellent Work!"
3246 Ettie St #4, Oakland, CA 94608
CA Licensed & Bonded Contractor #1010577
tel:+510.821.2742
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