What kind of clay is a ceramic dish made of?
Ceramic or slurry containers are produced from a combination of clay and several types of soil and other materials such as kaolin, quartz and quartzite, types of feldspar, silica, stoneware soil, and sometimes from calcium carbonate, zinc oxide, and talc.
What is the difference between a ceramic dish and a clay dish?
The difference between clay and ceramic dishes is in the type of soil and the ability to glaze and the temperature they can withstand in the kiln. But ceramic dishes are made of mixed soil with less adhesion and high firing degree, usually more than 1080 degrees Celsius. Also, ceramic dishes are more glazed than pottery.
Ceramic dishes are made in three stages:
- Making the dish
- Glazing it
- Baking in the oven.
< /p>
1. Making the body of the ceramic dish
Suitable soil composition for a ceramic container:
In making a ceramic container, first, special soil is prepared with a mixture of clay soil, some soil and special mineral stone powder. The type of soil used and the size of each is different for each type of container.
It should be noted that if the impurities in the soil are too much, the ceramic container will crack and break when drying or cooking in the oven. As a result, the ratio of soil and stone powder should be obtained in the laboratory.
Clay preparation for ceramic container:
After combining different soils, they They are poured into a cylindrical mill and balls of hard porcelain or silk are poured into it and mixed with water until it becomes soft. which has a moving impeller, they are poured and passed through the sieve. Then the excess water is taken by the filter press machine. Finally, after leaving the filter press machine, the clay molds are kept in the clay warehouses for about a month until the necessary fermentation is done.
Creating a ceramic dish in the desired shape and firing it:
In this step, the prepared clay is used to shape the dish and then it is put into the oven at a certain temperature. to cook The oven temperature should be increased slowly.
2. Glazing ceramic dish
Glaze is a bright and transparent coating on ceramic and earthenware that makes them shine and beautiful and increases their resistance and strength. At the same time, the glaze is also used as a waterproof material.
The color and quality of the glaze depends on the type of its formula and its ingredients, the most mineral compounds that are used in the composition of the glaze include the following :
Iron oxide
Cobalt oxide
Chrome oxide
Copper oxide
Copper carbonate
Glazing steps on ceramic dishes:< br>
Glaze ingredients are first ground and then prepared in the form of a paste and at the same time thin liquid. Then they cover the ceramic dish baked in the oven with this liquid. After glazing, the dish is put in the kiln to be baked. Sometimes, for the second time, the dish is painted or painted with glaze and put in the kiln again, and in this way, the ceramic dish is even more beautiful and It also becomes more resistant.
The most important types of glaze for ceramic dishes:
Glaze has different types, including glossy or matte, transparent or cloudy, smooth or even textured. . For example, lead glaze is shiny and transparent, which cooks at a temperature of 800 degrees Celsius, and tin glaze is white and matte.
3. Baking a ceramic dish in the oven
The furnace is the heart of the ceramic production workshop and it accounts for the largest investment in any workshop or factory. The factors that should be considered in choosing the furnace are:
the product to be cooked
production rate
production quality
cooking temperature
cooking time
flame type
Fuel type
Note that if there is too much oxygen in the furnace, the color of the glaze will change. For example, the use of copper carbonate in an oxidation environment creates a turquoise color. However; If the oxygen in the air is low, the glaze will have a bright red color.