Clay, a material cherished by ceramics enthusiasts, is a natural mineral abundantly present across the globe. It's easily found in riverbeds, on cliffs, by roadsides, at the base of mountains, and even in the backyards.
This versatile substance is characterized by its fine texture, with minimal sand grains, making it ideal for crafting various shapes due to its excellent plasticity.
Clay comes in different classifications. The first is Primary or Residual Clay, which remains in its original location since its formation.
This type boasts exceptional high-temperature strength, with a melting point exceeding 1750°C.
Primary clay typically contains common components found in the Earth's crust, such as granite, which transforms into kaolinite through hydrothermal processes.
Kaolinite is a vital component in ceramics and is commonly referred to as china clay.
Secondary clay, also known as sedimentary clay, undergoes a different journey. It is carried by water flow or glaciers from its place of origin to new locations, where it settles.
During this process, secondary clay undergoes constant grinding and experiences the effects of climatic conditions, gradually evolving into fine, flake-like particles. This characteristic gives rise to various types of clay, such as ball clay, metamorphic clay, and alabaster clay, known for their exceptional plasticity.
Throughout its migration, clay can become contaminated by other substances. These contaminants impact both the color of the clay and its shrinkage after firing. The darkness or lightness of clay depends on the types and proportions of these contaminants.
Clay transported by glaciers, termed gravel, has never been carried by water. It remains encased in ice alongside rocks, stones, pebbles, and other contaminants. When excavated, it retains the components of these substances.
Secondary clays, on the other hand, gather various minerals and organic matter as they move. Red clays, for instance, contain high levels of iron oxide, a common mineral. Iron gives these clays their distinctive reddish hue.
Red clay has historically been widely used in pottery, particularly for household items, flower pots, and bricks, owing to its excellent plasticity and relatively low melting point.
Clay is a versatile material with a rich history in ceramics. Its availability in nature, along with the clear distinction between primary and secondary clay types, contributes to its wide-ranging use in the creation of ceramics and pottery.
Understanding the characteristics of different clay types and their origins can help artists and artisans make informed choices when working with this remarkable substance.
