Ceramics surround us day by day almost without realizing it: plates, cups, bowls … and although, in most cases, they are industrially produced, the source material is the same: CLAY.
And it is that although we all know that ceramic is fired clay, and that this clay is a mixture of clay and water, it is worth remembering that it is a natural material extracted from the mountains. Which after being treated becomes those containers that we have everywhere at home. But really, is all pottery made of clay? What is clay? Why do I have cups that are white? Isn’t clay always red? Let’s learn a little more about the main ingredient without which there would be no pottery!
Clay is the smallest particle that makes up the earth
The earth is a compound of mineral and organic matter that is found around the entire earth’s crust. It is divided into components larger than 2 millimeters (rocks, stones and gravel) and into smaller particles (sand, silt and clay).
Clay is the smallest particle (<0.002 mm) that makes up the earth, it is made up of minerals from the decomposition of igneous rocks over millions of years.
The main characteristic of these clay minerals compared to any other mineral is their plasticity and their ability to form a cohesive mass and maintain its shape once we have mixed it with the appropriate amount of water. Once dry it becomes hard again, and if it is fired at a minimum temperature of 800º it hardens permanently, transforming into what we call ceramic.
There is no single type of clay
Clay is a product of geological transformation, in which several factors have intervened, and this means that there are no two deposits in nature that contain exactly the same clay, even with differences between those that come from the same deposit. (Emma del Carmen Vázquez Malagón, 2005)
Despite this immense variety of clays that we can find, we are going to focus on five types that are especially notable for their use in ceramics: kaolin, ball clay, fireclay, stoneware and surface clay.
These clays have very different characteristics in relation to plasticity, melting temperature, color, etc. which we will have to take into account for its later use in a ceramic body.
And, these pure clays are rarely used alone, since some of their characteristics do not make them optimal for it. So the most common thing is to create a mixture of different types of clays together with other raw materials to obtain ceramic bodies, which are the ones that are currently packaged for sale in most ceramic stores.
Can I find my own clay on the mountain? Yes of course!
Throughout history potters from all over the world have found their own clay to create their own ceramic bodies, thus getting closer to the nature that surrounds them. By learning to recognize clay wherever we are, we will get to know better this material that we are surrounded by every day. So get ready because soon I will explain how to recognize clay wherever you are.
Bibliography Garcia Verduch, A., 1985, “Boletín de la sociedad española de cerámica y vidrio Vol 24, Nº 6.” Origen y composición de las arcillas cerámicas. Instituto de Cerámica y Vidrio, C.S.I.C. Arganda del Rey (Madrid). http://boletines.secv.es/upload/198524395.pdf
Origen y composición de las arcillas cerámicas. Instituto de Cerámica y Vidrio, C.S.I.C. Arganda del Rey (Madrid). http://boletines.secv.es/upload/198524395.pdf Vázquez Malagón, Emma del Carmen, 2005,
Materiales cerámicos: Propiedades, aplicaciones y elaboración. Ed. Universidad Nacional Autónoma de México, México. (Pag. 37)