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Glass Fusing And Slumping Techniques To Make Glass Patterns


Fusing glass is a key technique to master as a beginner when working with glass. Using this technique, you can create a range of finished pieces including jewelry, plates or even small window panels for your home. It’s the perfect technique to get creative, as you can add many other elements including different textures, iridescents and gold powders. There is no limit to the glass fusing patterns you can create!


What is glass fusing?

Glass fusing is the process of heating two or more pieces of glass together in a kiln in order that they fuse together. The kiln needs to reach between 760 and 815 degrees celsius in order to melt successfully and so it’s important that your kiln can achieve these temperatures.The difference in heating of certain elements of your project can lead to different textures being created and so good control over temperatures is important. Glass heated to a lower temperature to create texture is called ‘tack fuse’ and glass heated to the highest temperature to create a smoother finish is called ‘full fuse’.


What type of glass should I use?

One of the key components of successful glass fusing is selecting the correct glass to use. The glass needs to be resistant to breakage after being heated up and then cooled down in the kiln. You can purchase ‘fusible glass’ which is specifically made for this technique, so it’s not really possible to use offcuts from other projects as they are unlikely to be suitable. The best thickness for fused glass is ¼ inch thick, built in two layers, which will ensure that the glass doesn’t change shape when heated.


What do you need to master your glass fusing technique?

You will need to prepare before you undertake your glass fusing project. For a basic glass fusing project, you will need: a selection of fusible glass, a pattern, a glass cutter, grozing pliers, detergent cleaner, safety glasses and a kiln. You may also need a grinder if you are looking to shape your project.


The basic art of fusing glass - how is it done?

For your first project, start with something small like a coaster or decorative piece. The most successful method is to lay your pattern layer underneath another layer of glass to ensure a smooth flat finish. This is known as capping.

Firstly, sketch your ideas out on paper and keep it simple to start with - cutting art glass can be tricky. You can do something from your own ideas but there are also templates available on the Internet to help you.

Cutting the artglass to shape

Cutting the artglass to shape is a skilled technique in itself, involving scoring and carefully tapping/prising the glass apart to the required shape. Once you are satisfied with the size and shape of your pieces, clean each piece with a detergent to ensure no oily fingerprints are set in once the object has been fired. 


Loading the kiln

Place the finished assembled piece on ceramic fiber paper to ensure that the finished project does not stick to the inside of the kiln. As an example, the below schedule is based on a ‘full fuse’ with two layers of art glass up to 30cm square:

  • Heat the kiln up to 600 degrees celsius at a rate of 222 degrees celsius per hour
  • Slow the heating down to 111 degrees celsius per hour to prevent bubbling
  • Hold the temperature at 670 degrees celsius for 30 minutes
  • Then fire as fast as possible to 804 degrees celsius
  • Soak for 10 minutes
  • Hold at an annealing temperature for your kiln (based on your kiln manufacturers advice) for 30 minutes
  • Cool to room temperature at approximately 111 degrees celsius per hour

To avoid cracking the glass, it is best to be patient and ensure that the glass has reduced to room temperature before opening the kiln. You should also wait until the work has fully cooled before cleaning it, as using water could shock the glass and crack it.


What other glass fusing techniques are there and how do I master them?

If you wish to add some shape to your glass fusing project, you can use the slumping technique. This is the art of using a mold to shape the glass by heating it, so that it takes the shape of the mold. This is a perfect technique for creating glass bowls or decorative pieces.

There are 3 main methods of slumping.

  • Into a mold, which is balancing the glass on top of a mold and allowing the heat to ensure that the glass sinks into the mold and forms the finished shape. 
  • Over a mold, which is inverting the mold and allowing the glass to drape over the mold and to form the shape
  • Through a mold, which is essentially a ring through which the glass seeps through to create a shape.

Mastering these techniques involves some trial and error, particularly with the ‘through a mold’ technique as you need to make regular checks to see how far the glass has slumped. It’s also important to be able to control the temperature so that the glass does not slump too much.

There are also many materials that can be used for slumping molds including clay, steel and fiber blankets - it all depends on which works best for your individual project.

There are no set rules for glass fusing and slumping techniques. Results are dependent on the kiln, the size of the project, the number of layers, the desired finished look, and the type of glass used. For example, small items of jewelry can be fired and cooled quickly, even in as little as an hour but other projects involving slumping or larger surface areas can take several hours.


One of the key aspects to mastering your glass fusing technique is to have the appropriate glass fusing kiln available to heat and mold your project into its final state. Good control of the temperature is crucial as this will affect the finish and texture of your completed project.

At Soul Ceramics, we have an extensive range of kilns perfect for glass fusing projects, all with advanced temperature functionality to ensure consistent and well finished pieces. Much depends on whether you are using the kiln for a glass making hobby or for a commercial venture. Please contact us if you have any additional questions regarding the most suitable kiln for your needs.


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