Clay is just a plastic substance of mineral origin which consists primarily of hydrated aluminum silicates.
Depending on the source rock, there are many types of clay.
The clay is formed by the decomposition of rocks eroded due to different agents and the acquisition of these impurities to source material deposition.
Clay has some basic components are plastic and clay kaolin and a few other basic components that are antiplastics plastic or quartz, sand, pegmatite whose function is to act as fluxes, and therefore have a key role in the transformation process in the oven.
Depending on your use two types of clays:
• pottery clays.
• china clay (stoneware and porcelain refractory).
grades and qualities of different pastas are:
• Terracotta or pottery, fired at low temperatures, between 900 º c and 1000 º C. They are fine grain pastas and a great plasticity. This group includes the blue clay with a high lime content and when cooked and takes on a yellowish red clay that gets its color due to its high iron content and can be fired at 1100 º C. Once cooked Terracotta takes a red or yellow and porous is textured.
dishwashing • Pasta: they are very plastic, white or ivory and fired to 1200 º C. Its texture is porous.
• Gres and refractory pasta: pasta to which is added plastic materials such as fireclay, sand ... They are very resistant to high temperatures. Its plasticity is variable depending on the composition of the original clay and decrease in size in the process of drying and firing. Once cooked take on a yellow to gray, vitrified some elements of its composition and texture are slightly porous.
• Porcelain, ceramic-based kaolin, feldspar and quartz. Is semi-transparent white color, touch, sound, appearance and texture glazed waterproof.
All clays during drying and firing reduce its size. This decrease in size will be greater the lower the content of plastic substances in the clay.
highly plastic clays, with a fine grain, suffer a 20% reduction in the drying process so they are not very useful but very good for mixing with other clays that lack of plasticity in the case of ball clay or ball clay as the bentonina, which is also used to make us fat pastas plasticity.
In clays over plastic, very fat, scouring added grog.
