Using Copper Foil in Stained Glass Work

Long ago stained glass was crafted using lead to hold the glass pieces together. The process was messy and the lead came hard to bend it you wanted a more intricate design or had small pieces. When it was discovered that lead could result in health problems, it became even less desirable.

In the 19th century Louis Comfort Tiffany, heir to the Tiffany jewelry fortune, developed a brand new system of working with stained glass that would eventually take the place of the old leaded system in many modern studios. Called the "Copper Foil Method," it replaced the bulky lead came with thin strips of copper that had an adhesive on one side. This is the method we use and teach in our studio, Stained Glass One. Over the years we have had a lot of questions relating to using and storing copper foil, so I have developed some simple answers.

Why does foil come in different widths and backing colors?
Copper foil comes in several widths and backing colors, each best for specific applications. You need to decide which to use on a project-to-project basis. As a general rule of thumb, though, we recommend a 1.25 mil thickness, and a 7/32 inch width for our students. It is the "middle" weight and size of the usual available foils, and is suitable for most projects.

Thinner widths (3/16 and 5/32 inch) are best for tiny glass pieces that might be mostly covered by the wider foils, and get "lost" in the solder. Very textured or very thick glass works best with 1/4 inch foil. Some studios recommend this larger size for beginner students, but we do not.

Foil also comes with different colors on the adhesive side. If you are using cathedral glass (one you can see through) choose a foil with the color that matches the patina you intend to use in finishing the piece. If you don't, the foil backing will show through these glasses and make sections of your piece look different from the overall patina color.

Why are my solder lines so large?
Different sizes of foil create different width solder lines. Also, if you didn't cut your glass carefully, there could have been gaps between the pieces. The gaps fill with solder as you work. Next time, be sure to carefully grind the pieces to fit, or re-cut pieces which are too small.

Why isn't my foil attaching to the glass?
There could be several reasons for this problem: Did you clean the edges of the glass carefully before applying the foil? This is an extremely important step in the process, and one that many people neglect. You may also have difficulty getting the foil to stick if you have gotten oil or sweat from your fingers on either the foil or the glass. Heat and humidity can affect the stickiness of foil, especially if it wasn't stored properly. Finally, be sure you are burnishing the foil tightly against the glass with your fid to help keep the foil from pulling away from your glass.

What do I do if I have an uneven section at the end where the foil meets ?
This happens when the foil wasn't applied evenly, and is a very common problem. The easiest solution: use a sharp little hobby knife (like an Exacto) to trim off the uneven edge and make the seam line smooth.

How do I know if my old foil is still good?
If your foil is still in the unopened package, check the color of the outer layers. If they are dark and look tarnished, unroll some of the foil and check the inner layers to see if they are still bright. If they are, the foil is probably still good. You should also check the adhesive on the back of the foil. If it doesn't feel sticky any more, don't use the foil.

What is the proper way to store copper foil?
Keeping copper foil useable is mostly a matter of common sense. Unopened foil will last for a couple of years, and generally retain it's stickiness. Opened foil doesn't last as long because it can absorb moisture, causing it to lose its stickiness. It can also become oxidized (discolored and tarnished) making it hard to solder. To prevent these problems, if we have opened foil we store it in a zipper-locking sandwich bag, which keeps air and moisture out.

A word about foiling machines
On occasion we have a glass artist or new student ask us about using a foiler or foiling machine. We carry them in our store, but don't use them ourselves, even for big projects. Changing the foil when you want a different size, or adjusting the machine for various thicknesses of glass is more work than just hand foiling. Plus, we like the hand foiling results better...

If you really want to use a foiler, it takes some practice to figure out exactly how it works, and you will probably waste a lot of foil in the process. However, some glass artists swear by them, so you will need to decide for yourself if you want to use one. Maybe your local stained glass dealer will have one on hand for you to try before buying.

Foiling is one of the easiest steps in the stained glass process if you take the time to learn it properly. As with the other steps, the more you work with it, the better you will become.