One issue that many stained glass hobbyists face is choosing the right size of copper foil for the project they're planning. The choices can seem a bit overwhelming until the reasoning for why to choose one over the other presents itself.
One reader wrote to me and said, "Hi: I am wanting to set up my home glass studio and I have a question about foil widths. As I am shopping I am seeing various widths of foil. How do I decide which is right for my projects. Right now I am planning to create small to medium size pieces."
What options are available?
Before we can begin to discuss the answer to the question, I think it would be a good idea to go over what the possible options are. The size of copper foil tape for stained glass varies in width, thickness, and backing colours.
Width - The most common options include; 3/16", 7/32", 1/4", 5/16", 3/8", and 1/2".
Thickness - Copper foil is usually available in 1mm and 1.5mm thicknesses. Some are also available in 1.25mm thick.
Backing Colour - Foil backings are available in 3 colours; silver, copper and black. Normally the colour selected is determined based on the finished colour of the solder you plan to use for your project. If you are going to use black patina, then black backed foil would be the colour to choose.
Chracteristics of Good Copper Foil
Copper foils function is to allow us to assemble the glass pieces with solder. Since solder doesn't stick to glass, copper foil is used as the foundation to build on. If we think about houses for a moment, a poor foundation results in a poorly structured house built on top of it. The same goes for the foil used in stained glass with out solder on top.
The foil needs to be flexible to form around all of the shapes we want to make with glass. This means that it needs to be a little stretchy so that it won't tear or split when forming to inside curves.
The softness of the foil is also important in allowing it to stretch but I've personally noticed that softer foil sits smoother and takes the shape of heavy textured glass much better too.
The copper foil should also be strong and adhere well so that we can burnish it (rub it smooth) and remove all of the kinks without tearing it accidentally.
Consider these four things when deciding which size of copper foil to use.
The Size of Your Project
An appropriate size of copper foil for most projects is somewhere in the 3/16" to 1/4" range. Anything wider used for the whole project will likely look heavy compared to the size of the piece, even for larger panels.
The Thickness of the Glass
The thickness of the art glass should be considered because we need to ensure that enough of the foil wraps to both the front and back of the glass to create stability in the piece. In essence, when we solder the front and back of a project at seam, we are making our own "i" beam.
It's fairly commonplace that many, especially those earlier on in their journey of making stained glass, believe that the stickiness of the foil holds the project together. But, this is not the case.
The solder seeps between the pieces and when enough solder is added to the front and back, it makes a shape that secures the glass in place (hence the "i" beam analogy. )
Should the solder be too thin, there is no structure because it is essentially a metal piece of tape. Building up the solder is what adds stability to the foil. The photo below shows a piece of lead came. It's a visual example of what the solders purpose is meant to achieve when a stained glass piece is fully soldered.
The final width of a seam (with proper fitting pieces of glass,) is determined not by how much solder you use, but how wide the foil is and how much extends to the front and back surface of the glass.
The Overall Appearance of the Piece
After determining the basic structural needs of the project, the next consideration is the "look" you're aiming for.
Do you have a personal preference toward heavier lead lines? You may be more inclined to choose a wider foil.
Should the piece feel lighter in appearance? If so, then you are much more likely to choose narrower foil.
Using various width foils in any given stained glass piece will help create emphasis or focus on the area(s) that have a heavier foil. It may be used to add more detail by separating the foreground from the background, or to outline a subject to draw attention there.
My Personal Preference Of Copper Foil Widths
When I had a gift shop for my glass on Etsy, I was making tiny little angel ornaments. Because the glass part measured only 2.5 inches tall (about 6 cm,) I chose to use a smaller width of foil since the 7/32" was too overpowering and made it look clunky in my opinion.
Here's a photo of one of those angels using 3/16" foil.
So there you have it! In a nutshell, there are some things that need consideration when deciding which copper foil to use. However, there's also room for personal preference of the look of the finished piece too.
If you're keen to learn more about incorporating various foil widths in one project, there is an online workshop that I hosted in the spring of 2020 for Makers Club members that goes a little further in describing how foil sizes can add subtle effects to your artwork. You can find details about the workshop here.
Did you know? Makers Club members get automatic access to all past workshops. Learn how to become a member.