A microwave kiln is a device that crafters use to fire small art projects in a microwave oven. While some crafters use it to fire ceramics or process precious metal clays, the most common use is to fuse small pieces of glass as part of the jewelry-making process. This type of kiln has numerous benefits — namely cost, time efficiency, and convenience — but its potential safety risks prevent many in the crafting community from embracing it.

Most microwave kilns measure between six and nine inches (about 15.24 and 22.86 cm) in width, and three and five inches (about 7.62 and 12.7 cm) in height. They are cylindrical in shape and consist of a base piece and a cover made from a combination of ceramic and refractory board. Refractory board is a material that can withstand high temperatures and act as an insulator.

To use a microwave kiln, crafters place the object to be fired on the base and then put the cover on. The kiln is then placed in the microwave, which is run until the piece has been completely fired. Once the process is finished, the kiln is immediately removed from the microwave and left to cool on a heat-proof surface.

There are a number of benefits to using a microwave kiln. It is significantly cheaper in price than a traditional kiln, and it requires a great deal less energy to operate. While the firing time varies based on the size and type of the project and by the wattage of the microwave, the process is generally brief, typically achieving fusion in 15 minutes or less. The microwave kiln also offers its user the promise of convenience, as it can be used in almost any home.

The microwave kiln does possess a number of potential drawbacks that lead some crafters to question whether its usefulness outweighs its risks. Number one among these concerns is the fact that the kiln heats up to approximately 1,650 degrees Fahrenheit (about 899 degrees Celsius) while in use. Temperatures at this extreme could cause damage to the microwave or serious burns to the user in the event of mishandling or malfunction.

Potential exists for the microwave kiln to transfer harmful substances to the inside surfaces of the microwave, as well. In order to prevent this occurrence, most microwave kiln manufacturers recommend maintaining a separate microwave dedicated solely to kiln projects. To minimize the potential for accidents, it generally is recommended that all microwave kiln users thoroughly review manufacturer instructions before kiln use.