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What Is Kilnforming And How Does It Work?

Kilnforming is the process of shaping glass in a kiln, using the heat from the kiln but also the natural pull of gravity.


What is the difference between glass fusing, glass slumping, kilncasting and kilnforming?

Essentially, glass fusing, glass slumping and kilncasting are types of kilnforming. Kilnforming is the general term that covers any process by which glass is heated in a kiln and its form is changed.

blue glass on a beach


How does kilnforming work?

When glass is heated in a kiln, it softens and the consistency becomes runny - almost like honey, thick and sticky.  Further increases in temperature causes the glass to liquify even more.  This is where gravity comes in. The liquid glass fills out the space and creates a new shape, or fuses with other colours or types of glass in the kiln.


Types of Kilnforming

Fused glass

Glass fusing is one form of kilnforming. Glass fusing is essentially joining two or more pieces of glass using the heat of the kiln, causing the glass to be 'fused'. There are a number of different techniques for making fused glass, such as “tack fusing” which is where the pieces of glass are heated until they are hot enough to fuse but don't change their original form.

A "full fuse" is where glass is heated to the point that it is in liquid form and is fused with other pieces of glass, changing its original form.


Kiln Casting

Kiln casting is another form of kilnforming. Kiln casting is the process of creating a glass object in a kiln by heating it above or inside a mold until the glass becomes liquid enough to fall over the mold or into it.

Kiln casting lends itself to being creative with the mold. You can create a number of different kiln formed glass shapes including glass for practical uses as well as artistic.


Glass slumping

Glass slumping is another kilnforming process that uses the heat of the kiln and gravity to slump a sheet of glass into a mold. Slumping glass lends itself to a number of different possibilities.

The process works by heating the glass in a kiln into a liquid form. The force of gravity then pulls the glass towards the floor of the kiln. In the way of the floor of the kiln is a mold, which the glass slumps over to create the shape.

Once the glass has dropped into the mold and formed its shape, it is cooled back down to room temperature (often referred to as annealing). Once the glass has cooled, it retains a solid form in the shape of the mold that it has slumped upon.

Slumping is commonly used to make objects that can be used for food and drink including bowls, glasses and plates, but there are a number of things that can be created using this method including works of art and statement pieces.

pieces of glass on a white table


What can be created using kilnforming and what is it used for?

Kiln formed glass can be used to create a number of artistic possibilities. It can be used to create different textures, patterns and glass effects by using the heat to form different shapes or in different styles of mold. Many artists use different glass effects to create visually striking pieces and some modern art pieces are created out of kiln formed glass.

Kiln formed glass is a highly versatile product, and can be used for both decorative or structural purposes, internally and externally. Kiln formed glass can also lend itself to a wide range of textured finishes such as sandblasting, etching, different colours and mirroring.

Common uses for kiln formed glass include art pieces or fashionable products for the home but they are also used in a practical sense for things such as office partitions, splashbacks, feature walls and lighting. The possibilities are endless.


What type of glass can be used for kilnforming?

Although there are many types of glass that can be heated in a kiln, there is a specially manufactured type of glass called "kiln glass". This type of glass is specially made to be used in a kiln and lends itself to fused glass, whereby it connects with other types of glass in the kiln with ease.

glass pattern in many colors


How can you undertake kilnforming?

Kilnforming glass opens up a range of possibilities. It can enable artistic creations to be made but equally it can produce practical solutions that are kiln formed. Kiln formed glass can also be used in a commercial sense, if you are looking to make a business out of it.

If you would like to experiment in making different glass products that are kiln formed, you are going to need a glass kiln. At Soul Ceramics, we have a range of glass kilns and glass casting kilns perfect for different kilnforming techniques. If you would like more information, please do not hesitate to contact us.

Further reading: A step by step guide to bottle slumping