Introduction
Under a somewhat wide definition, kilns have been around for roughly 20,000 years, with the oldest known pottery dating back to the ancient Near East1 Modern kilns turn clay into food-safe and usable ceramics without heating sources directly touching the samples. The controlled heating environments can reach temperatures upwards of 2500°F (1371°C) – necessary to dehydrate the clay, vitrify feldspars inside the claybody and melt glazes onto ceramics. Bisque firing – a temperature range of 1623-2048°F (884-1120°C) – turns the clay into a frail and dehydrated ceramic in which the feldspar in the claybody has not yet melted to seal the surface. At this point, the ceramic inversion has taken place, clay is transformed to ‘ceramic’ and water is heated from the porous clay so that it can accept glaze easily. Following this process, the now-ceramic material can absorb glaze to make the product safe to eat and drink from after firing. Kilns heat up varying clay and ceramic samples in order to create objects (used to eat, drink, hold water, etc.) that cannot be achieved by other heating methods.2
These heating structures come in many sizes from ones that can hold a single mug to thousands of mugs, plates, and bowls. Ceramic shelves are placed inside the kiln to prevent different ceramic pieces from touching, and evenly distribute mass throughout the kiln for even heat application. Kiln types include electric, gas, and wood-fired, each allowing for unique conditions that may alter the appearance of the finished product3. Small electric kilns rely on the use of a 120/240 V plug and the use of alloy metal heating elements. Inside, the kiln is a high-temperature-resistant ceramic material (firebrick, often soft) with pins to keep the heating elements in place. A stainless-steel band is used to hold and compress the sidewalls. Additionally, all the external hardware is attached to the bands, except the controller. The control system has evolved from a witness cone kill switch to an automated system, protruding from the front of the kiln, that controls the internal temperature of the kiln. The controller applies voltage to the heating elements in the kiln to maintain a temperature ramp that is determined by the thermocouple, a temperature-sensing probe inside the kiln.4
Heating elements have a wide range of uses from toasters to hair dryers. Typically, heating elements are composed of metals, which are used to resist electricity to heat up the desired area. Ceramic kilns use metal heating elements, which are often inserted into grooves inside the kiln walls. Heating elements come in various metal compositions, ranging from metals and alloys,
