Starting from this base, the potters work with 2 types of mud, natural and prepared.
It´s the one we can use with only a minimal cleaning. The primary clay is the purest, but also the least "plastic" given the structure of its particles. Therefore, the secondary clay, subject to changes and movements, is more plastic. It should be noted that it is rare to use natural mud on its own, so they are usually combined with other materials to achieve a better balance between resistante, cooking and shrinkage.
- Primary clay or kaoling: Is not very "plastic", but is the common component in clay pastes and glazes. Its vitrified version, known as maloquita, is what is used as a chamotte in many clay pastes.
- Clay ball: Is the name with which it is also known the secondary clay. By itself it is very plastic too. If it is cooked, it adopts a white color, being one of the basic elements for the obtaining of the porcelain and the stoneware.
- Stoneware: It is very difficult to find it in its pure state. In the common case, it is a mixture of secondary clay and other minerals that allow improving its quality. In the natural state it presents a grayish color, which happens to white once cooked.
- Red mud surface: It is the most common among natural muds.
- Refractory mud: It is known to be used to be exposed to high temperatures. It is extracted from veins close to the coal and can be used alone or mixed with other clays. It is also usually used to obtain chamotte once cooked, ground and reduced to grain.
- Bertonite: Is a mineral very similar to the ceramic that is usually added to different clay types to improve plasticity.
It´s an artificial mixture of natural muds and other raw materials. Refining, grinding, cleaning and impurities are aliminated before packaging and distribution. In this way, one achieves the quality and propertiesdesired by the manufacturer, being able to offer directly for different applications or uses. Our advice is to choose those products that can guarantee the same quality in the medium-long term beacause, over time, the deposits are depleted and it is very difficult to find others with similar characteristics.
Generally, manufacturers of prepared mus usually classify their clays as follows:
- Porcelain: It´s the whitest of all pastes, acquiring translucent tones if it´s thin. The cooking index is between 1240 and 1350ºC.
- Stoneware: This is a fine clay and easy to work, especially around. It´s cooking rate is between 1240 and 1350ºC
- T Material: Is a very plastics paste, whitish and with a high proportion of moloquita. This allows to create pieces resistant to the thermal shock because it withstand without problems the deformities. To date, the T material of english origin is the best quality.
- Low Temperature Paste: It is sold in red or white colors and it´s necessary to vitrify it if it´s to be water resistant. Its cooking around 1000-1180ºC