The Differences and Similarities Between Oven, Kiln, Forge and Furnace

The method of heat that you use to harden or dry your project is entirely dependent on what your project is and what your end goal is. In general, any project needs to achieve a certain temperature and remain there for a concerted period of time. There are different types of heat treating methods available on the market, but the predominant methods used are either an oven, a kiln, a forge or a furnace.

What is a kiln?

A kiln is generally used for the heat treatment of pottery, ceramics or glassware. A kiln can reach immense heats from a standing start, and generally the items to be heated remain in the kiln for the duration. The definition of a kiln is a thermally insulated chamber, and they have been used for centuries, predominantly to harden or dry materials.

What is an oven?

An oven is another form of heat treating, but it can reach lower temperatures than other heat treatment options. A heat treat oven can be used for steel which requires a less powerful heat than ceramics or glass in order to subvert its form.

What is a forge?

A forge is generally used for metalwork, as it is an open fire source whereby the metal can be placed in, heated to temperature and then ‘forged’ into shape. It is perhaps the most traditional form of heating a project to temperature.

What is a furnace?

A furnace is essentially another form of oven, but it can reach much higher temperatures and is suitable for working with metals to help change their form. Generally, a furnace holds metal at a high temperature for a considerable period of time. Items being fired are often added to or removed from the furnace when the unit is hot. There are some longer periods of time when the temperature of the furnace is held during the firing, and there can be multiple cooling steps and hold times for processes including annealing, case hardening, and tempering.

Oven vs Kiln vs Forge vs Furnace: What are the differences?

Essentially a kiln works as an enclosed oven that can heat to very high temperatures. It does not melt or subvert the form of the item enclosed within and is therefore most suited to drying out ceramics and clay or adding a layer of glaze. It works efficiently as many of the modern kilns can be heated up and maintained at a certain level or pre-programmed depending on the project. Soul Ceramics offers an extensive range of electric powered kilns, ideal for small and large scale pottery and ceramic projects. 

A forge acts as more of an open fire pit but can also come in the form of a forging oven. Forges are generally used for shaping metals while hot. Rather than being enclosed in a vessel, normally metal (or sometimes glass) is heated inside a furnace and then taken to a forging press and pressed to a desired shape. Forges can range in size from small open pits to large industrial processes.

A furnace heats to extreme temperatures and can therefore process a number of different types of metal finishing including annealing, smelting etc. Furnaces are generally used on a more industrial scale to heat large scale steel projects and are therefore less suited to domestic projects.

Ovens come in a range of different forms, from domestic through to commercial, but there are also many heat treat ovens available, specifically designed to reach and maintain certain temperatures. Ovens can be used for pottery but do not always reach the heat required for ceramics. Heat treat ovens are ideal for heat treating steel as they do not reach the extreme heat of kilns or furnaces but can maintain a steady temperature to heat the steel throughout.

The above heat treating sources all carry out similar functions, either through the purpose of drying or heating to help to harden or change the form of the project being fired. The type that you use for your own personal project is dependent on what you wish to achieve and what your source material is. At Soul Ceramics, we supply a range of kilns and ovens suitable for ceramic, metal and glass work, with advice available to ensure that you achieve your needs.

Additional resources on ovens and kilns

• Things to consider when buying a microwave kiln
• A knife maker's guide to Evenheat heat treating ovens
• A guide to temperature ranges for kilns