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Stained Glass Basics

stained glass

Stained glass has been around for thousands of years in one form or another. It has been used in religious institutions, residences, commercial buildings and anything in between. Understanding what stained glass is and what it isn’t as well as how to repair it and maintain it can be invaluable since the time and cost to create new stained glass projects can be quite high.

In this post, I’ll cover some of the basics of stained glass including its history and how to repair and maintain it. If you’ve got a stained glass window in your home this post should be a good primer to help you get started.

The History of Stained Glass

The oldest stained glass windows in the world are thought to be the Prophet Windows in Augsburg Cathedral, c.1065. Long before the double hung windows and casement windows so common in our houses today, the first stained glass windows were in religious institutions like churches.

Before modern times, stained glass was durable because the glass was thicker, often broken into pieces with chisels, and usually set in cement. Painting on glass was the norm, thus the term “stained glass” was developed as a craft that not only referred to the color of the glass, but also the “firing” of designs on glass. It was easier to work with large pieces of glass because of the thickness, and designs were often more intricate because of the painting. Those who created windows (mostly for churches), were truly artists, as they had to be able to depic scenes and especially people (body and facial features, etc.).

As time passed, glass was mouth blown into cylinders and then flattened into sheets by hand. This provided thinner sheets of glass that could be more easily cut. As the stained glass process evolved to use lead channel instead of cement, another aspect of the craft called “leaded glass” was created (often used interchangeably today). There is a difference however, and there’s more you need to know, too.

At the turn of the 19th Century, huge innovations in glass making using machines were used to flatten and create a more uniform thickness to glass. Textures, layers, and more colors were added, and today there’s a wide selection available.

For the DIYer or restoration professional, this is good news! Matching glass from 100 years ago is not as difficult as you might think. There are some other issues that need to be taken into consideration, but repairs are easily accomplished with the right skills and know-how to fix those missing pieces or cracks in that stained glass window that came with the recent restoration project you’re working on.

Types of Stained Glass

There isn’t just stained glass and leaded glass though. There are a plethora of variations on art glass and architectural glass that can make a project truly unique, and difficult to match if you don’t recognize the technique or the product. Stained glass and art glass are available across the internet for order and I’ve listed some fo the site below that have a wide variety to select from.

Finding the right pattern and color can be tough if you’re trying to match a historic piece of glass. The best way I have found is by utilizing the help of local pros. Bring a sample of the glass you need to match to a local stained glass or art glass studio and ask the pros there. They’ll usually know by seeing you sample exactly what you need or what will get you close.

Their encyclopedic knowledge of the topic is immensely helpful. You’ll get an answer like, “Oh yeah that’s Bullseye Light Aventurine Green” which will sounds like a foreign language but you cab usually trust that they know what they are talking about.

Lead, Zinc, or Copper Foil

Other than the original works of institutional arts that were held together in cement there are three main materials that most stained glass is constructed with.

Lead

The traditional leaded glass window is constructed with pieces of glass held in place by lead cames, which are an H shaped channel that the glass slots into and can be bent into the shapes the artisan desires dues to its softness. Joints where the lead cames intersect are soldered together to connect and strengthen them.

Lead is immensely versatile and as such was the most commonly used materials for cames. Strong, durable, yet flexible it has a centuries long lifespan. In larger projects the lead can be problematic without the addition of rebar like supports run across the interior side of the stained glass window to prevent the lead from sagging.

Be careful when working with lead cames as just like with lead paint, sanding, cutting or even simply handling lead can cause ingestion if you don’t use the proper PPE and wash your hand throughly with a soap designed to remove heavy metals like lead.

Zinc

A stronger option for stained glass is using zinc cames which look about the same as lead except that they are shinier initially. Due to their increased strength and less flexibility zinc is often used for the outer borders of leaded glass projects where the strength is needed.

Zinc cames are also an excellent choice for designs with more straight lines and fewer curves since bending zinc cames is not nearly as easy as bending lead cames. Frank Lloyd Wright used zinc heavily in his stained glass designs since they were more geometrically inclined.

Copper Foil

About the same time that glass making was evolving into thin sheets, Louis Comfort Tiffany, the famous stained glass maker from the last 19th century, developed another process called “copper foil” which many hobbyists use to create stained glass.

The process of copper foil involves wrapping each piece of glass with a copper tape, burnishing it securely to the glass and then soldering all the foil to construct the panel. While technically this is still a stained glass process, it was used primarily to create his wonderful lampshades, as it provided an inventive way to “curve” a design into a 3-dimensional dome because of the smaller pieces and copper foil.

You can often tell the age of the old window based on what type of lead (or copper foil) was used in the construction. If a panel is made with copper foil, it is likely from the 20th Century (or later), as this is when copper foil became more popular. Zinc is a relatively newer material in stained glass compared to the long history of lead.

anatomy of stained glass window
Courtesy nps.gov

Stained Glass Preservation and Repairs

The next question, of course, is “Should I restore?” Preservation is always the first choice, but depending on the condition of the window it might be better to add support and fix the cracked glass. Other options include taking the window apart and replacing worn out sections of cames to restore it to its original beauty.

If you’re a traditionalist, it’s always good to preserve as much of the original as possible, but sometimes the old lead is too soft or damaged. In addition, lead has evolved, and today is stronger, as well as the putty (cement) used to hold the glass in place. This may make it more feasible to replace the lead entirely. If there’s only a few cracks, or they are not noticeable (especially from a distance), there are invisible (clear) glues that can be added to the glass to keep the glass in place.

If you haven’t worked with stained glass or leaded glass before I would recommend finding a local studio and taking a few classes. Unlike a lot of the restoration trades this is one skill that has a lot of local training available for DIYers a most studios have classes open to the public.

If you find the work suits you then by all means tackle the restoration of your stained glass. If you do plan to restore it yourself here are a few tips to help when working with stained glass.

Tools

Pick up a few basic tools to make sure you’re prepared for the work. This simple set of tools will allow you to start with some basic repairs and restoration work.

Basic Techniques

The stained glass is held together by the soldered joints which can be cut free with the mini hack saw if need be. Often the solder joints are the main failure points and the joint needs to be completely cleaned, the old solder removed, the lead polished clean and then the joint can be soldered again. Only completely clean lead, free of dirt and tarnish can be successfully soldered.

Then the cames can be packed with cement or in many cases glazing putty is used. This is just a mixture of linseed oil and whiting which provides cushion, strength and water sealing to the cames and joints. Packing the cames with some glazing putty ensures a good seal.

For sagging stained glass even simple techniques like laying the panel flat in the direct sunlight can help the lead settle back into place. Helping it along with some heavy books or something else to weight it down can speed up the process. Once your glass is back into the proper shape adding a piece of rebar to the back side that is soldered to the lead and connected to the window sash or door will help hold things tight to prevent sagging in the future.

I hope this post has been a helpful primer for you on stained glass to see if this is something you may want to dig into a little deeper. I want to thank Sue Rae at RaeGlass.com for help in putting together the information in this post. Her years of experience with stained glass has been instrumental is teaching me the ins and out over the years.

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