Products made from natural materials are clean, environmentally friendly and, as a rule, have an original appearance. And if they are also made with their own hands, their materials will keep the warmth of the master's hands for a long time. Clay products are especially in demand. But in order for them to be strong, and the material itself does not crack, the clay solution must be enriched with additives.
What is clay
Clay is a sedimentary rock. In a dry state, it is dusty, and when moistened, it becomes plastic. It contains one or more minerals of the kaolinite or montmorillonite group, but it can also contain sandy compounds.
Clay is predominantly gray in color, but there are varieties of white, red, yellow, brown, blue, green, purple and even black. This is due to the substances contained in each type of clay. Depending on the same substances, the fields of application of clays are also different.
Since this rock has high plasticity, fire resistance, excellent sinterability and good waterproofing, it has found wide application in pottery and brick production. However, often, clay products at the stage of modeling or drying, or at the final stage - firing - crack. This can happen for several reasons: the clay is dry, the clay is "skinny", that is, there is a large admixture of sand in it, or, on the contrary, the selected grade is too "fat".
Clay Mortar Additives
In order to prevent the possibility of cracks forming on the product, it is necessary to select the “correct” grade of clay from the very beginning. Ideal for pottery blue and white clay. But sometimes the right choice of material is not enough.
If the product cracks due to insufficient moisture, the issue is solved by simply adding water to the clay solution.
However, sometimes the clay product cracks due to the excessive "fat content" of the solution. Clays with high plasticity are called "fatty". When soaked, they give a tactile sensation of a greasy substance. The dough made from such clay is shiny, slippery and practically does not contain any impurities. In this case, the so-called "emaciated" substances are added to the solutions from such clay: "skinny" clay, burnt brick, potter's battle or sawdust and sand - ordinary or quartz.
But there is also the opposite situation - the product cracks due to too "skinny" clay. Such material is non-plastic or low-plastic, rough to the touch, has a matte surface and easily crumbles even with a simple finger pressure. It contains a very large amount of impurities in the form of sand, earthy dust particles. In this case, it is necessary to carry out the opposite operation - add more fat to the "lean" clay or use other additives that increase the fat content of the solution, for example, glycerin or chicken protein.
There is another method - to agitate the solution. Its essence lies in adding water to a solution and mixing it thoroughly. The solution is allowed to settle. Water remains in the upper layer, which is drained. The next layer contains liquid clay, and underneath it is unwanted additives. Liquid clay is carefully scooped out and poured into a basin, leaving it in the sun to evaporate excess moisture. The result is plastic clay with the consistency of a tough dough.
