What is kilnforming?

Kilnforming is using kilns to change the shape, texture or form of glass. There are lots of operations that can be done using a kiln, including bending, painting, slumping, fusing, casting, raking. You can make jewelery, ornaments, bowls, platters, sculptures, architectural features—an enormous range of items—through kilnforming.

Working with glass

Artists and craftspeople work with and manipulate glass in a variety of ways through a range of processes and techniques; and through a wide range of temperatures.

Cold glass At the “Cold” end of the glass spectrum is the taking of ready made glass and joining it by lead lighting or copper foiling: simple methods of joining pieces of glass into intricate designs from the small window hanging or mobile, to ‘Tiffany’ style lampshades, to domestic window and door panels and vast installations in churches and public buildings. On a grander scale it includes the taking of large slabs or chunks of clear or coloured glass, cutting to shape and joining together using steel concrete or chemical bonds to create structures such as the roof in the Great Hall at the National Gallery in Melbourne
Hot glass At the “Hot” end is glassblowing: skilled artists manipulating molten glass into intricate delicate and beautiful shapes. The glass is melted in furnaces, frequently re-heated during manipulation in a ‘glory hole’, and shaped using a wide range of tools: the origin of many of them being traceable back many centuries. The molten glass can also be poured into moulds to create diverse objects which may be sawn ground or polished. Conventionally the melt is made in the studio from the basic ingredients of glass, known as "batch" but more recently small pieces or chips of glass made elsewhere may be remelted in the studio.
Warm Glass In between is the  “Warm” zone, involving the re-working of ready made glass. Most operations involve the use of a kiln, although some tasks such as making beads and stringer are done using a torch. Even there, a kiln is used to anneal the final product. Kilnforming is generally taken to include all those operations involving a kiln in which glass is heated and shaped in the same operation. It can thus include ‘glass casting’.

The three areas of Art glass above described are often defined in those terms, so that a studio specializing in one area will be referred to as a Cold Glass, Warm Glass, or Hot Glass Studio. This doesn’t mean that the three are always separate and distinct. Kilnformed glass shapes can be used in a lead light creation.  A blown shape can be included in a kiln-cast creation. The combinations are many and varied.

Flameworking or lampworking.

This involves the use of gas torches as a heat source in processes as diverse as bead making, sculpting large blocks of glass, or manipulating glass rod or tube to make animals figures or complex laboratory and scientific apparatus.

Kilnforming processes

Here’s a brief description of key kilnforming processes;

1. Bending: Heating glass to change its shape without altering the surface texture and clarity. Usually done over or into a mould in a kiln.
2. Slumping: Using heat to soften glass so that gravity causes it to change shape or to take up a changed surface texture.
3. Fusing: Heating two or more pieces of glass together so that they melt sufficiently to bond together as one piece.
4. Painting: Using special paints to decorate glass. They can be fired into the glass at temperatures ranging from fusing to below bending.
5. Raking: Heating glass to above fusing temperature and then using tools to make patterns in the molten surface.
6. Casting: Using moulds to give shape to broken or molten glass.It can be done in open moulds, where small pieces of broken glass are allowed to fuse together to create a ‘honeycomb effect ('Pate-de-Verre' or paste of glass), or by pouring molten glass into preheated moulds, or by other techniques.

Types of glass used for kilnforming

Almost anything which can be called ‘glass’ can be used for kilnforming. We have all seen the ‘flattened’ bottle. Broken bottles can be used to make glass castings, pate-de-verre, or to make stringer and frit in a ‘flower pot kiln.

Commercial kilnformers use window glass called float glass to create textured panels for shops offices restaurants. Glass artists use the same glass, with or without the addition of paints, to create all sorts and sizes of architectural and decorative pieces. Both glass artists and hobbyists use the vast range of compatible fusing grade coloured glass from suppliers around the world. Still others use the even more extensive range of coloured and textured glass produced for leadlighters. Truly, the range is enormous!