A glass crucible is a durable and heat-resistant container used to melt glass in a kiln for the purpose of creating glass pieces by casting, blowing, and other processes. These devices are made from refractory materials, specialized brick, ceramic, and other compounds that are able to resist the extremely high temperatures of the kiln. They are available in a range of sizes and designs for different applications. For people who have access to the right raw materials, it is also possible to make a glass crucible.
The crucible looks somewhat like a large flower pot, and some may have holes in the bottom for casting activities. A dish can slide under the crucible to catch drips, a potential issue if the device is overloaded or a problem occurs while the glass is melting. Molten glass can damage a kiln, especially if it is allowed to accumulate, and users must be vigilant to prevent spills when working with a glass crucible.
To use a glass crucible, the operator loads it with glass and inserts it into the kiln, bringing the kiln temperature up to a working heat appropriate for the type of glass. Extreme heat characterizes glass kilns, and care must be taken around the crucible and kiln to avoid injuries. When the glass melts, the glassworker can start working with it with the assistance of tools like crucible tongs to safely grip the glass crucible from a distance.
Some glass crucibles have a lining to prevent sticking. Such linings can introduce impurities and cannot be used with certain kinds of glass processes where purity is critical for the integrity or appearance of the glass. In other cases, glass will stick to the sides of the device, and the operator will need to clean it after use to remove adhered glass and prepare it for the next firing. Operators also regularly inspect their glass crucibles for signs of cracking, pitting, and other issues that might compromise their performance.
Choosing a glass crucible requires thinking about the type of glass that will be handled, the size of the kiln, and the kinds of projects involved. Instructors and mentors can help people with the selection of an appropriate crucible if they are not sure about which product would be most appropriate. As people develop experience and skill, they may gravitate toward a particular brand on the basis of their experience with it, and could accumulate a collection of crucibles for different needs.