The origin of the clays that are part of the SIO-2 ceramic clays is the subject of recurring questions from users. In this blog we explain it to you.

Clays are the natural minerals that make up most of the composition of ceramic clays. Thanks to their physical-chemical characteristics, they provide the plasticity necessary to shape pieces and allow obtaining a durable finished product after firing in a ceramic kiln.

Clays are sedimentary rocks that come from the decomposition or weathering of other pre-existing rocks thanks to the action of atmospheric agents, basically water, ice, and wind. Clays are the finest particles resulting from erosion and weathering and accumulate in sedimentary basins that can have a large geographic area. The geological process of weathering, transport and sedimentation has occurred uninterruptedly since the first atmospheric agents appeared on planet Earth, billions of years ago. It is a recurring process that today we can observe every time a large storm occurs. The reddish colour of the water in rivers and streams is due to the clays that the water carries in suspension. In this case, the clays that we see will end up accumulating at the mouths of rivers, in flood zones next to their beds or, simply, at the bottom of reservoirs.

The clay deposits currently used belong to large sedimentary basins formed in the geological past that have been protected from the subsequent action of erosion and weathering. Each clay deposit has characteristics that depend on the origin of the rocks that formed it and the physical-chemical changes that have occurred in the deposit itself since its formation until today. These factors are what determine the characteristics of each clay deposit and no two deposits are the same in the world. This makes each clay exclusive and only found where nature has decided.

Spain is a country very rich in ceramic clays. The geological history of Spain has been very generous, providing large deposits of clays with very diverse characteristics and of great interest for ceramics. It is no coincidence that Spain is a world power in ceramics, both in industrial ceramics and artistic ceramics. They are very varied sites, mainly formed during the secondary and tertiary era. Among others, the kaolinitic clays from the Teruel mining basins stand out, with exceptional plasticity and refractoriness characteristics.

Likewise, the rise of the ceramic industry in Spain, fundamentally related to the manufacture of ceramic tiles in the Castellón de la Plana area, has led to the availability of high-quality clays and minerals from other countries.

The history of Cerámica Collet is closely related to the industry and pottery in the Barcelona area, linked to the high quality of its red clays used for low-firing ceramics. Although in the past clays from various deposits in the area have been used, currently, the largest deposit of red clays is located in El Papiol, 20 km from the Esparreguera factory, and was formed during the Miocene (tertiary era), about 10 million years ago.

It is an enormous quarry, exploited by the company Suministros de Arcilla S.A., since the 40s of the last century, and, since then, Cerámica Collet has benefited from the quality of its clays. Currently, most of the low-fire SIO-2 clays are made up of clays from El Papiol, among which the popular traditional red clay PF stands out.

It is important to note that clay deposits, including El Papiol, contain several types of clay and it is the know-how of geologists, mining technicians and exploitation operators who determine which typologies are marketed and for what uses they are most suitable. Thus, not all clays are suitable for ceramics. It is very convenient to use several types of clay, even from the same deposit, to formulate ceramic clays and compensate for any technical differences that may occur during their extraction from the deposit. It is essential to extract the clay in large batches and make the appropriate mixes to guarantee that the final clay is within the specifications that have been established. This is the basis to guarantee that the ceramic paste will have a homogeneous and regular behaviour over time.

Of course, clay deposits are exhaustible resources, so their availability is conditioned by their use and size. Although Cerámica Collet works with reliable clay suppliers who exploit large deposits, sometimes the clays run out or their properties change. If necessary, ceramic clays are reformulated to minimize changes, but these are inevitable in some cases. It must be added that environmental restrictions on mining make the availability of these natural resources increasingly delicate.

On the other hand, clay deposits are, in turn, an ideal medium for hosting inert waste landfills. Thus, the volume left by the extracted clay is replaced by material from demolitions and other construction waste. In this way, the site performs a double function and the final landscape of the quarry, once restored, is not affected. This is also the case of the El Papiol site.

In this blog we have focused on the El Papiol clay deposit due to its importance in the manufacturing volume at Cerámica Collet. However, we use clays from many other sources, among which we highlight those from the mining basins of Teruel, widely used in the ceramic industry, as we have explained.

We hope you liked this article. You will find more interesting articles in the “Information” section of our blog.

The clays are extracted from the quarry using big excavators.

Once extracted, stockpiles are formed to homogenize the properties of clay.

The El Papiol quarry is large and its clays are used for multiple uses, beyond ceramics.

The restoration plan for the El Papiol quarry is carried out thanks to the dumping of material from demolitions and other construction waste.

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