One of the most common questions stained glass hobbyists face is: what size of copper foil should I use? With so many copper foil widths available, it can feel overwhelming at first — but once you understand the reasoning behind each size, the decision becomes much easier.

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’m 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.”

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What Sizes of Copper Foil Are Available?

Before we dive into choosing the best copper foil for stained glass, it’s helpful to understand the options available. Copper foil tape comes in different widths, thicknesses, and backing colours — and each factor can affect how your finished piece looks and performs.

• Width: Common copper foil sizes include 3/16", 7/32", 1/4", 5/16", 3/8", and 1/2".
• Thickness: Most foil is available in either 1 mil or 1.5 mil thickness. Some brands also offer 1.25 mil options. Thicker foil holds its shape better but may be harder to burnish neatly.
• Backing Colour: Foil comes with three main backing colours: copper, silver, and black. The backing colour you choose usually depends on the patina or solder finish. For example, if you’re planning to use black patina, then black-backed foil is the best choice for a seamless look.

Characteristics of High-Quality Copper Foil

The primary purpose of copper foil in stained glass is to create a surface that solder can adhere to. Since solder doesn't stick to glass directly, the foil becomes the essential foundation for building your project. Think of it like the foundation of a house — if it’s weak or uneven, everything built on top is compromised.

To do its job well, stained glass copper foil needs a few important qualities:

• Flexibility: Good foil must wrap smoothly around curves and corners without tearing. Slight stretchiness helps it form neatly around inside curves and detailed shapes.
• Softness: Softer copper foil conforms more easily to textured or uneven glass surfaces, giving you cleaner, more consistent lines — especially important with heavily textured glass.
• Strength and Adhesion: High-quality foil sticks well and can handle firm burnishing without lifting or tearing. It should stay in place even while you’re smoothing out wrinkles and preparing it for soldering.

How to Choose the Right Size of Copper Foil

There isn’t a one-size-fits-all answer, but these four considerations will help you choose the best copper foil for stained glass projects:

1. Size of the Project

For most stained glass projects, a foil width between 3/16" and 1/4" works well. Using anything wider throughout an entire project may cause the lines to appear heavy or bulky — even in larger panels. Narrower foil helps maintain a more refined and balanced look.

2. Thickness of the Glass

The thickness of the stained glass is important because the foil needs to wrap far enough onto both sides of the glass to provide a secure surface for soldering. When we solder both sides of a seam, we’re essentially creating a miniature "I-beam" — a structure that gives the piece strength.

Many beginners mistakenly think it’s the foil’s adhesive that holds everything together, but that’s not the case. The strength comes from the solder. As it melts, it flows between the foiled edges and, when applied generously to the front and back, it hardens into a shape that locks the glass in place.

The image below shows a piece of lead came, which visually illustrates the kind of strength we aim for with properly built solder seams:

Keep in mind, it’s not the amount of solder that determines the width of a seam — it’s the foil size and how much of it wraps around the glass edges. Proper fitting and appropriate foil width give you solid seams without adding unnecessary bulk.

3. Overall Appearance

Once structural needs are met, think about the visual impact you want. If you like bold, strong lead lines, you might prefer a wider copper foil. If you're aiming for a more delicate or lightweight look, opt for narrower foil instead. The foil size directly affects the final aesthetic.

4. Artistic Design

Using various foil widths in a single piece can help guide the viewer’s eye. Heavier foil lines can add emphasis, and create visual separation between the foreground and background, or frame elements like a subject or focal point. It’s a subtle way to add design interest and depth.

My Personal Preference of Copper Foil Widths

For the most part, my projects are made using 7/32" copper foil, and my go-to brand is Edco for straight foil. I also occasionally used New Wave foil by Venture Tape, which had a single wavy edge that added an extra dimension or detail to the finished seams.

Note: New Wave foil is no longer available, but I recently came across this look-alike option on Amazon with a 4.7-star rating. I haven’t tried it myself yet (I still have some original New Wave left), but it could be a good alternative if you want to experiment.

When I had a stained glass gift shop on Etsy, I made tiny angel ornaments that were only about 2.5 inches tall (6 cm). In those cases, the 7/32" foil looked too bulky, so I opted for 3/16" foil to give a lighter, more delicate look to these pieces.

So there you have it! When it comes to copper foil, your project’s size and structural needs matter—but there’s also some room for personal taste in the finished look.

Copper Foil Size & Colour Options

Here are some popular copper foil options you might find useful. I’ve included the ones I use most often as well as some alternatives you may want to explore:

This post contains affiliate links. If you choose to purchase through these links, I may earn a small commission—at no extra cost to you. I only recommend tools I’ve personally used, thoroughly researched, or would confidently add to my own studio.