Overfiring
Overfiring is a phenomenon that occurs when a ceramic piece is subjected to excessive temperatures or prolonged firing times, exceeding the recommended limits for the clay or glaze used. This problem is more common when kilns are used without precise automatic controls or when times and temperatures are not properly monitored. It can also occur when materials with different maturity points are combined, generating internal stresses that result in fractures or structural failure.
This process can lead to a number of undesirable effects, such as warping, excessive vitrification, cracking or even melting of the part, which can adhere to the kiln shelves and cause significant damage. In glazed pieces, overfiring can cause the glaze to become too fluid, losing definition in the decorative details and creating residues that affect the kiln.
Although generally considered a mistake, overfiring can also be used intentionally in artistic ceramics to explore unexpected textures and shapes. In these cases, the aim is to take advantage of deformations and dramatic effects as part of the creative expression.Interesting Fact
In some ancient ceramic traditions, such as Chinese high-temperature ceramics, the accidental overfiring of certain pieces led to the discovery of unique decorative effects, such as the development of natural glazes from kiln ashes. These effects, initially considered defects, were eventually valued for their uniqueness and were deliberately incorporated into ceramic aesthetics, marking the beginning of techniques such as ash glazes.Helpful Tip
Use pyrometric cones to verify the actual kiln temperature, especially if you are experimenting with new materials or glazes. Be sure to follow the manufacturer's specifications for clays and glazes, and test small pieces before undertaking a large project. If accidental overfiring occurs, clean the kiln immediately to prevent residue from affecting future firings.
