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 Posted: Tue Nov 18th, 2008 10:43 pm
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Tod:  The overlapping of plates may also work to strengthen a window.  The combination of the integral fins embedded between the plates is the strongest.  We have added clear, plate glass plates on Tiffany and La Farge windows, combined with fins, to add structural support. 

 Posted: Wed Nov 19th, 2008 08:33 pm
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Yes, strategic placement of larger plates over areas of smaller pieces of glass augments the structure of a window or a particular area of a window.

I think that the benefit of foiled windows is not the copper foil itself, but rather the fact that the entire surface is floated with solder. I have also seen tinned lead in windows, which outlived lead that was not tinned.

We recently restored an 1893 plated window designed Donald MacDonald, leaded not foiled. The majority of the lead was fairly small, 3/16” flat with some smaller leads here and there. Most of the lead showed severe deterioration, lead carbonate etc. (see photo)
Soldered to the deteriorated lead, there was some lead that had been tinned. The tinned lead showed no signs of deterioration, fatigue or anything else. (see same photo)

Many, if not all, of the Tiffany windows I have worked on, have had floated perimeter leads which again remain in excellent condition. As you chisel the putty away, the lead underneath is shiny as the day it was soldered. During restoration, I have always reused the tinned lead and it re-solders beautifully. My friend and fellow craftsman, Dan Maher, once told me that he always floats the perimeter leads on windows he designs and creates.

I’d love to hear if anyone else out there has come across the same thing, and if anyone else has any thoughts on the subject.

Serpentino Stained Glass

Attached Image (viewed 385 times):

Tinned lead.jpg

Last edited on Wed Nov 19th, 2008 09:10 pm by Roberto

 Posted: Thu Nov 20th, 2008 02:07 am
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Hello Roberto,

I've been following your posts and have appreciated the depth of sharing and detail of thought. I suppose I have more questions than answers to offer.

Copper foil is really pretty amazing when you think about it, an adhesive clings this thin film of copper to the edge of glass, is completely solderable and becomes the matrix that holds pieces of glass together. Every chip, slight irregularity of cutting, glass variation of thickness is beautifully covered by a bead of solder. It is almost an extension of the glass.

Lead, on the other hand, seems totally clumsy in comparision. A uniform medium, now distictly separate from the glass, requires putty for water proofing and strengthening. Without this glazing process, pieces are loose. Lead does not grasp and hold glass in the same way copper foil does, even with the benefit of re-bars.

You mention the durability of Tiffany windows. My first thought was about the thickness of the copper film, of the copper foil used back then. I know very little about the Tiffany studio, did they make their own foil? Was it pure copper or various hardners included? Just like his glass, did Tiffany have other secrets?

I would venture to say that if two identical panels were made, one with lead the other with copper foil, the copper foil one would be lighter in weight. Could this weight factor also contribute to the longevity of copper foil work and why lead tends to fail ?

My preference too, is to work in lead. And as you point out, it may require a long term committment of time and money. It's tragic flaw and the price you pay for the art.

I am thinking now of cathedral windows and the myth that lead windows need re-leading every hundred years or so, or at least some flattening. It sure would keep us all in some kind of work. However what if it was meant to require routine maintenance? They say the windows in Chartres cathedral hum. It don't know for certain if this is true, however if you think about the huge sails of glass, these windows create, wind, rain and snow would apply a lot of pressure on the glass, as would gravity, once you're up a hundred feet or so. It's essential that the lead can expand and contract, even deform with constant external pressures, and be resiliant enough to hang onto the glass, until it fails. In this regard lead out performs copper foil. And with routine maintenance, these types of failure could be prevented.

Routine maintenace requires man power, expertise, money and a dedicated relationship with glass. In our disposable nature of society, this kind of tending to, is a foreign concept. In an economy that will likely see the closing of some studios, how can long term committments be made with maintenance as part of the service we provide?

This doesn't really address why Tiffany's windows are in as good a shape, as they are. They are much smaller than cathedral windows and as Tod points out, have plating for added strength. Could one argue that the chemistry of opalescent glass is more durable than european antique? I certainly have come across glass that has difficult to cut, of both sorts. Likely an annealing issue. Did Tiffany and his glass makers have a few other secrets about the very making of the glass? There are so many possibilities for exploration. Like I said, more questions than answers.

This has been an excellent excercise and I hope others jump in.

 Posted: Thu Nov 20th, 2008 02:20 am
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This link will get you to the real inventor of the copper foil method,M1

 Posted: Thu Nov 20th, 2008 02:07 pm
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Vic wrote: This link will get you to the real inventor of the copper foil method

Absolutely fantastic! Thanks, Vic. And thanks, Roberto, for your thoughts. Certainly we have all seen the terrible condition of lead in the rabbet compared to the solder joints there. Dan's idea would seem to have merit. But, I suppose this is not something a restorer should "add" to a window?

Historical sidebar:

I, and others here, I'm sure, started sg work before adhesive-backed foil was available. When I decided to try foil, I bought a roll of 6" wide copper sheet (.001" thick) x who-knows-how-long from Admiral Brass & Copper, I suppose. I still have some of that. The purchase was made in the late 1960's. Mostly, I tinned pieces as I foiled, no adhesive at all.

Early in the '70's, some clever soul began using 1/4" foil swiped from the custom slotcar hobby field. This foil had horrible adhesive which oozed out when heated, had to be trimmed with a blade and often pulled completely free of the foil! Retailers asserted that the purpose of the adhesive was mostly to keep the foil on the glass until you could solder it. Salesmen will tell you anything, eh?

- Tod

Last edited on Fri Nov 21st, 2008 03:17 am by Rebecca

 Posted: Thu Nov 20th, 2008 09:11 pm
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Dear Elizabeth,


You mention "Myth"  and in one of your statements " the longevity of copper foil work"   Is there evidence that copper foil outlasts leaded windows?


A couple of things that worry me about copper foil windows are, how long does it take for the adhesive to deteriorate and how do you make the windows waterproof without having external glazing, especially in the case of stone mullioned  church windows? 


If there is no external glazing the stained glass held by inflexible copper foil will crack and leak due to the  weather,  another problem is,  in UK architects would not normally recommend sheets of glass on the outside of their Gothic church windows because of the reflection from the sun, the alternative, such as polycarbonate is even worst as it deteriorates after a comparatively short period.


Best wishes,



 Posted: Fri Nov 21st, 2008 04:47 am
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Thanks for the link Vic, very interesting. I thought I would weigh in on a
few things. Roberto, I tin my outside leads to resist corrosion caused by
the environment of wood frames. Organic acids from the wood, possible
of nasty little critters that might also cause oxidation. As you mentioned,
and I think most of us have noted the perfect condition of the soldered
joints of perimeter leads and the rest of the lead severly deteriorated.
Most of the Tiffany and LaFarge windows I have restored had tinned leads
I noted the perimeter leads being in better condition. It seemed like a
idea to tin the perimeter leads so I do it on all restoration projects. In
my new work I tin all the leads. Again, Tiffany and LaFarge seemed to think
it was a good idea so I do it. I think it strengthens the lead and I get a
nice even patina. It takes a few extra minutes but I think it is worth it.
have also noted on cabinet doors oxidation on the leads on the inside
surface. I think this is probably caused by the wood. So again I do cabinet
doors in copper foil, or tin all the leads.
Catherine and Roberto and copper foil, I have also noted the good
condition of copper foil windows. Seemingly they are weakest when there is
big window with big pieces involved. Maybe the expansion and contraction
stresses a few key joints. But in windows of high complexity they are
usually in good shape. In leaded windows of high complexity there is
buckling. I always say buckling occurs because it can. Leads that create
general patterns or lines across windows make "hinges" where the lead can
distort. Of course horizontals are the weakest followed by diagonals and
circles and sometimes a series of diagonal corner frame patterns act like
circles and distort. How support bars work in concert with the leads is
another discussion.
I agree with previous mentions about foil windows being lighter and the
soldered foil lines are much stiffer than lead. When leaded windows are new
and the waterproofing is strong the glass in the leads has a harder time
pushing out of plane. Design lines that wave back and forth also make
buckling more difficult than with straight lines. But as the waterproofing
loosens and the forces of expansion and contraction occur the buckling
happens in leaded windows. In copper foil windows any wave or wiggle in the
design line reduces the opportunity to hinge and reduces the buckling. The
foil and sloder conform right to the edge of the glass so even tiny shapes
that corrugate the line make it much stronger. I use both copper foil and
lead in my new work and sometimes mix the two together to get different
effects. Like a good drawing I think the variety of lead and copper foil
lines make for a tasty image. Dan Daniel Maher Stained Glass

Posted for Daniel Maher by Rebecca

 Posted: Mon Dec 8th, 2008 03:12 am
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a belated thank you for your fin supplier recommendation .. and to Vic for his...

style="BACKGROUND-COLOR: #ccccff"the subsequent dialogue about using fins in windows has been most interesting and informative too by others.

style="BACKGROUND-COLOR: #ccccff"The window in our studio is 6'w x 10'h,..had multiple horizontal support bars (interior) throughout, as well as fins in numerous locations  (exterior) .  Also there were many small round support bars around medallions... at  the top of the arched panel.... and the entire window failed... almost 80%of the wire ties separated, and the window started to accordion collapse on itself.  The only temporary saving grace was plexiglass that was installed on the outside and inside sometime in the 1990's  ( per the owner).

style="BACKGROUND-COLOR: #ccccff"everyone's commentary is much appreciated.

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