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How to Control Fused Glass Edge Quality

What’s volume control, and why is it important?

Glass Fusing Refresh

Great glass work is the product of a strong foundation and knowledge base. So, let’s go back to the basics and make sure you’re clear on the fundamentals that produce consistent, high quality artwork.

Fusing Fundamentals-Beyond Basics

Wherever you are in your glass fusing journey, newbie or advanced artisan, I believe we can all benefit from reviewing construction basics on occasion. Here’s why: 

Excited newbies are usually so eager to cut glass that they don’t really hearthe guidelines and they lack the experience to realize the relative importance of these recommendations on their finished project. While advanced crafters are absorbed in the creative process and the end result, to the point that they can go blind to the practicality of solid construction. 

Then there are those dare devils who’ve stumbled onto glass fusing and are immediately hooked. They dive right in giving little, if any, consideration to protocol. You know who you are. You fire first and ask later. 

No matter how you came to call yourself a fuser, this is for you.

Let’s start at the beginning.  

Glass Fusing- Defined 

Glass fusing is the process of taking compatible glass, stacking it to make a pattern or design and then firing it in a kiln until the glass melts together. Simple, right? Now, let’s build from there. 

Glass Fusing Fundamentals  

Volume Control – The Foundation for Quality Work  

What’s volume control, and why is it important?

Volume control is the relationship between how a project is assembled and its finished size, shape and thickness after fusing. It’s a formula you can use to accurately predict how your project will look and feel after it’s been fired. 

Let’s say you want to fuse a series of glass tiles to make a back-splash for your kitchen. But you can only fit 20 tiles in your kiln at one time, and you need 200 tiles to complete the job.

With what you’ll soon learn about volume control, every tile from the first to the last will match beautifully. Or let’s say you have a tropical fish pattern you’d like to work into a larger project. Here, the size and shape of the finished piece is very important to you. If the fish shrinks or grows in size, it could ruin the entire design. 

Another thing to consider, is whether or not you intend to slump your fused glass. The fused glass must fit neatly inside the mold, not on the rim, or it will slump unevenly to one side. This is where volume control comes into effect. With it, you’ll know how to compensate for any potential growth in advance of fusing your glass. (A good rule of thumb is to measure the mold and then cut your glass ¼ inch to ½ inch smaller than that measurement.) 

You have choices when it comes to how to assemble your projects. Different methods of construction will result in different project characteristics. Our goal here is to give you the tools to make educated decisions when selecting your technique so you have greater control and more satisfying results.  

How Glass Reacts to High Heat

Fused glass seeks a thickness of ¼ inch. That means a project made with a single layer of 1/8” thick glass will shrink. When it shrinks, the edges roll in and can become sharp. This shrinkage causes inconsistencies in the glass thickness. It’s usually surprisingly thick around the perimeter and thin in the middle. A project made by layering two pieces of 1/8” thick glass is likely to retain its original size and shape and will have a consistent thickness throughout. While a project made by layering three pieces of 1/8” thick glass will grow. When it grows, the shape distorts, and a square becomes a bad circle.  

Before starting a project, ask yourself how it will be used. If it’s an ornament, a single layer might be your best method of assembly due to the loose, free form shape and its light weight. If the piece is intended to be a decorative bowl, the two-layer assembly would be my choice. It has a clean, rounded edge quality and is consistent in thickness throughout. Now, if I were making a patterned sheet of glass to cut up with my saw, I’d go for the three-layer approach. In this example, the finished size and shape of the fused glass blank is irrelevant because the fused glass will be cut up.

How the placement of accents effect the size and shape of fused glass.

My Building Process

Most of my work is assembled with the two layer, plus accent method. I refer to the bottom layer as the base and the second as the design layer. The base layer and design layer are the same shape and size. The base layer is often a single piece of clear, but not always; sometimes it’s made up of cut pieces. The second design layer can be a single piece of glass, but often, its pieces fit together to make a specific pattern or design. The third accent layer is minimal, and it usually consists of small fusible elements that enhance the design theme. I choose to build this way because I get consistent results time after time. The finished size and shape of the artwork is predictable. The pieces come out of the kiln with beautiful, rounded edges and a consistent thickness that is both attractive and durable.   

It’s All Good   

Keep in mind, there’s no single right or wrong way to make any project. Personal preference, design style and function, should all play a role in helping you decide which approach is best. The objective is to consciously choose your fabrication method based on a solid understanding of the medium, rather than on a whim. 

There are always exceptions to the rules. The minute I make finite rules for myself, I break them. So, I’ve learned not to box myself in. You shouldn’t either. 

Enjoy the journey. The destination will take care of itself.

Watch the video here.

Read more about Volume Control here

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Happy Fusing!


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