kilnfiring

Kilnfiring is the process of heating materials in a kiln to high temperature to cause hardening, vitrification, sintering, or fusion. It is used in ceramics, brick and tile manufacture, cement production, and some metals and refractories.

In ceramics, firing follows drying. A typical schedule includes a bisque firing to harden ware, then a glaze firing to mature surface coatings. The temperature, time, and atmosphere determine color, strength, and texture.

Temperature ranges and atmospheres vary by material. Ceramics glaze firings commonly occur around 1000–1400°C; stoneware around 1200–1300°C; porcelain often 1300–1400°C. Atmosphere can be oxidizing, reducing, or neutral, affecting glaze colors and body phases.

Kilns differ by energy source and design. Electric kilns use electric heating elements; gas and oil kilns burn fuel to heat the chamber. Common kiln types include beehive or bottle kilns, updraft/downdraft kilns for pottery and bricks, and industrial tunnel kilns or rotary kilns for high-volume production.

In cement, clinker is formed in long rotary kilns at temperatures near 1400–1500°C, then ground with gypsum. Firing also densifies bricks and other clay products through sintering and vitrification. Kilnfiring is energy-intensive and requires precise control to avoid defects.

Safety and environmental considerations include heat and burn hazards, gaseous and particulate emissions, and energy use. Modern kilns employ insulation, temperature control, and emission controls to improve efficiency and reduce pollution.