How to Choose Copper Foil for Your Stained Glass Project

The copper foil technique is one method of attaching glass pieces together to form a single unit. It was developed by famed stained glass artist Louis Comfort Tiffany in the early 1900's. The process involves wrapping individual glass pieces with a thin strip of adhesive-backed copper, forming them into the desired pattern, then soldering along the seams to connect the various pieces and create a finished panel or other project.

Before you can begin to foil your stained glass pieces, you will need to determine what size and type of copper foil you need. Foil is available in widths ranging from 5/32 inch to 1/2 inch. You should choose a size that will fit the edges of your glass and not overlap too much on each side. The most common width used to achieve this balance is 7/32 inch, and this is the size we use in most of our projects. It covers most glass well but still leaves a nice thin solder line on the completed project.

Which Size Foil is the Best?
Some people, especially beginning glass artists, find the 1/4 inch width a little easier to wrap and center around their glass. They feel the larger width makes it easier to attach the foil and fold the edges smoothly and correctly. While this is true, it also means that centering the foil well is more important with this larger size because so much will show on either side. The main problem with using this size foil is that the edges showing in the finished project will be larger and more dominant than those created with thinner foil. This will result in thicker solder lines between your glass pieces. Remember, you are making a stained glass project, not a copper foil project! In our studio we feel it's better to learn to use 7/32 inch foil right from the start.

The smaller sizes of foil, 5/32 and 3/16 inches, are used mainly when you have an unusually thin piece of glass to foil, or when the pattern piece itself is extremely small. Under these conditions, using the larger sizes would cover so much of the glass that the color and pattern might get lost when you coat the foil with solder.

Why Does Copper Foil Come in 3 Colors?
Copper foil comes in rolls, and has a copper side which faces outward, and an adhesive side which is applied to the edge of the glass. This backing is available in several different colors. The backing is on the adhesive side of the foil so, when the foil is wrapped around a piece of transparent glass, the backing color is visible if you look through the glass "inside" the foiled area.

This sounds like a small detail, but when you patina your solder lines, a different color foil backing could be very obvious through transparent (cathedral) glass. If you are using an opalescent glass, which is very dense, the color of your foil isn't as important because the foil doesn't show through. Otherwise, this is the general rule of thumb: If you plan to use copper patina, use copper-backed foil. If you plan to leave the solder its natural silver color, the silver-backed foil will match. If you will be using black patina, go with the black-backed foil. By choosing matched foil and solder finishes, you eliminate a colored solder line with a "halo" of copper showing through.

Two Little Foil Tips
Over time, most glass artists use a variety of colors and sizes for their projects. Store your open rolls in zipper-closed sandwich bags to prevent tarnish. Whichever size foil you choose for your project, here is a tip that may save you time and frustration: Once a roll of foil is out of it's wrapper, you can never be sure what width it is when you pull it out again. Using a black marker, write the size inside the roll on the cardboard rim. That will end later confusion and save you time and aggravation if you use more than one size foil.

The copper foil you use to edge your glass pieces will be the conductor for the solder, which will hold everything together. Choosing the correct foil is essential to the overall success of your stained glass project. If you still have questions about the best foil for your project, check with your local stained glass retailer.