What is Fusing?

All Glass is Fusible!
Any glass will melt in a kiln when you heat it up; fusing glass successfully depends on knowing how different glasses work together. In our never-ending quest to "Make it Easy," our Delphi Experts have compiled the following pointers to help you make your next masterpiece ... in fused glass!

Coefficient of Expansion
A Coefficient of Expansion (COE) is simply a measurement of the rate that glass will expand and contract when it is heated and cooled. To fuse multiple pieces of glass together, it's important to use glass that is compatible. Fusible glass manufacturers test their glass to guarantee the COE (sometimes referred to as "tested-compatible"). To avoid stress-cracks and breakage, it is very important to use glass that has the same COE.

The two main COEs for fusible glass are 90 and 96. The main difference between the two is that 96 is generally softer and fuses at lower temperatures than 90. Regardless of the COE you decide to work with, you will have an amazing selection of colors to use in your palette.

Test Firings
An invaluable shortcut to getting the result you want is to make test firings. Simply cut small pieces of the glass you plan to use in a project and fuse a test tile. This will help you predict any color shifts and ensure compatibility. For instance, some glass colors "strike" (change color) when they are heated: Bullseye's Light Pink is pale lavender and strikes to a beautiful bright pink.  Many fusers keep track of test firing for easy reference. For your convenience you can print a firing log sheet from Delphi's Tips and Techniques web page.

96 is Great for Beginners
96 COE glass is excellent for beginners because it has a longer working range that provides more gradual heating changes. 96 COE glass gets softer as it gets hotter, then it becomes more rigid as it cools, with a smooth progression and predictability. Of course, these easy to work with properties also make it a favorite with many advanced artisans.

90 Offers an Incredible Selection
Looking for a huge color palette? 90 COE glass has been used by glass artists for many years, resulting in an amazing selection of color that has been developed for fusers. Delphi offers hundreds of types of 90 CEO glass. In addition to the colors there's plenty of dazzling effects, including textures, streamers, feathers and streaks. Not to mention iridized and dichroic coatings, frit, confetti and stringers!

Organizing Tip
If you are going to use glass with different COEs, plan ahead by creating separate storage areas for each one. The Glass Caddy (#7151) is a great tool to keep it apart: just label one caddy "COE 90", and the other "COE 96."

Jennifer Bonesteel

Thursday, March 20, 2014
Delphi Expert
188 Posts
Top Contributor Gallery Artist

@speakspoke we don't have any experience with using either of these products in a blown glass application. We believe that decals are likely to burn away in the heat of the torch. Flexiglass matures much like regular glass and reacts something like frit or enamel would when used with binders like liquid stringer or other glass medium. Again, we aren't sure about the use of either of these products with a torch but we'd love to hear about your results.


Wednesday, March 12, 2014
1 Post

Hello, I am a glassblower and was interested in the applications for flexiglass and decals on blown pieces. Also, what temperature does flexi glass mature?

Jennifer Bonesteel

Thursday, February 27, 2014
Delphi Expert
188 Posts
Top Contributor Gallery Artist

@bburton the line between the two pieces of glass will easier to see after grinding, especially if there are distinct color differences in the layers of glass. A fire polish in the kiln can help to minimize the distinction but it can't always be entirely eliminated. For an appropriate fire polish schedule see DelphiGlass.com/glassfusing.


Wednesday, February 26, 2014
1 Post

In regard to fusing jewellery, what is the tip to minimize the fuse line? Do they appear because of grinding? If grinding is needed what is the tip to eliminate, or is there one?


Friday, August 23, 2013
1 Post

I d like to know if the 90 coe dots are compatibles to float glass coe 88? thank you I m from Buenos Aires Argentina


Sunday, December 5, 2010
1 Post

Your introduction to fising was very informative I just wish it had went farther. I had a new kiln delivered about 6 months ago and it has set in my shop and never been turned on.