The Temperature Sweet Spot for Glass Fusing

The Temperature Sweet Spot for Glass Fusing

Fused glass is an incredible medium that offers artists and designers the ability to create a wide range of textures and effects through different firing temperatures and schedules. By programming a kiln to different temperatures, artists can create everything from smooth, polished surfaces to three-dimensional works of art. In this blog post, we'll explore some of the different temperatures we use at Fuse Muse Fused Glass for firing fused glass and the textures that can be achieved.

A word about Kilns and the temperature for achieving different stages of Texture in your glass.  Please keep in mind that all kilns are different and so the temperatures given are an approximation. To be safe,  give 5° on either side of any temperature given. So for a full fuse of COE 96 glass you should consider your kiln could do this anywhere from 783°C to 793°C or 1441°F to 1459°F. So remember each kiln is different and has it's own personality, but I am pretty certain they all worship the same kiln god we pray to each time we open the lid. 

Tack Fusing

Tack fusing is a technique that involves heating glass to a lower temperature than full fusing, just enough to fuse the pieces together but not enough to smooth out the edges completely. For COE 96 glass, this is at about 732℃ or 1350℉. This allows you to create a range of interesting textures and effects. For example, when small pieces of glass are arranged on top of each other and fused together using a  tack fusing program,  they can take on a bubbled or pebbled appearance. Tack fusing can be effective when creating jewelry or small decorative pieces where a more three-dimensional look is desired. This ornament is one I used to make years ago.

Tack Fused Inukshuk

One of the advantages of tack fusing is that it allows you to create designs with more depth than is possible with full fusing 2 layers alone. By adding frit (small pieces of glass divided by size) of small size, you can give glass a rough feel, imagine like a very coarse piece of sandpaper. By adding larger frit and increasing the heat or time slightly at your top temperature, you can make a smooth to the touch feeling like stones made smooth by rushing water. By using different sizes and shapes of glass, you can create art pieces that incorporate a large range of different textures and colors. 


Slumping is another technique that involves heating glass to a specific temperature in order to create a desired effect. Slumping involves shaping a piece of glass over a mold or form. Slumping actually takes place at about 675°C (or 1250°F) for COE 96 glass.  By programming the kiln to this specific temperature, the glass is softened and allowed to take on the shape of the mold. Slumping also depends on the size of the piece of glass involved. If it is smaller, it can be harder to get a piece to fully drop into a mold and so you may have to increase the temperature or the hold time. Fusing is an exact science, but there is always some variable that can be adjusted to meet your needs.  

Green striped dishes that have been slumped

Slumping can be used to create a wide range of different shapes and forms. For example, artists can create shallow bowls by slumping glass over a curved mold, or more complex forms by using more intricate molds.

Contour Fusing

Similar to tack fusing, contour fusing entails heating the glass to a marginally higher temperature. As a result, the glass's edges can fuse together while still retaining some of its texture and shape. With this method, a variety of intriguing textures and patterns can be produced, including a "relief" effect in which the fused glass appears to be elevated off the surface. 

Contour fusing is the term used for many degrees of melting glass. Therefore it becomes closer and closer to a full fuse by holding it longer or by increasing the temperature, or both. If there is some texture to the finished, cooled glass, it would be considered a contour fuse. 

Contour fusing takes place anywhere from 700°C (1292°F) to 765°C (1410°F).

snowman ornament with scarf being Contour Fused

An example of contour fusing can be seen in this ornament above.


Contour fusing can be particularly effective when creating pieces with a three-dimensional design. By fusing multiple layers of glass together using contour fusing, artists can create pieces that have a depth and dimensionality that is not possible with flat, two-layer pieces. This technique can be used to create a range of different effects, from subtle textures to more dramatic relief designs. 

Full Fusing

Full fusing involves heating the glass to its melting point, causing it to fuse together completely into a single piece. This technique is often used when creating large, flat pieces of fused glass, such as wall hangings, bowls, platters or table tops. One of the advantages of full fusing is that it creates a smooth surface, rounded edges and smooth corners, making it ideal for displaying intricate designs and patterns. 

Full fused plates soft corners and edges

One of the considerations when full fusing is the size of the glass once it has cooled. Glass will automatically flow to a thickness of ¼” or .6 cm. This is what glass does when heated. If you have only one thickness of glass (⅛”) and it is taken to full fuse temperatures, it will curl the edges and dog bone, which is a way of saying the glass will pull in where it is thinnest. If you have 3 pieces of glass stacked on one another, then upon heating to full fuse temperatures you will have the base becoming larger as the overflow stretches past the initial boundaries set out. So if you started with three squares on top of each other, you will get a circle that is larger than the squares you started with as the glass tries to get to ¼” thickness. 

Glass becomes fully fused when it reaches a temperature of about 788°C (1450°F). This is a common fusing temperature for COE 96 glass fusers. 


Did you know you can actually boil glass? Molten glass is free flowing and exists in a liquid state. It can boil through, whereas the bottom layer rises up and bursts through the top layer. It can also be raked, a term for pulling a metal “rake” through the glass, exposing different layers and creating beautiful folds of glass and color. You can try both these techniques but you must ensure your safety first by using heat resistant gloves, special eye protection and if possible specialized clothing that provides protection. 

Molten Glass that has been Raked

As a new or experienced fuser you will need to know these different temperatures in order to get the results you are hoping for. So when you begin to design your piece it is best to know your schedule in advance. I would suggest keeping a logbook of all your firings with pictures that will allow you to revisit your previous pieces. This gives you a reference point to start when programming your kiln and will give your pieces a better chance of producing beautiful glass art. 

Thank you for taking the time to read our blog post! If you'd like to explore our website and check out the fantastic range of fusing supplies we offer, simply click here. We hope you find everything you need to fuel your creative passions and embark on exciting crafting projects. Happy fusing!



Blog Owner Lisa Martin


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I am a fused glass artist from Sarnia, Ontario. I am so glad I found your website. It is full of great information.

Judy Robinson

I am a fused glass artist from Sarnia, Ontario. I am so glad I found your website. It is full of great information.

Judy Robinson

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