Ceramic tiles: production technology and types of products

The high performance of ceramic tiles is due to careful research into production technology, but the main reason is the firing temperature of the tiles, which varies from 950 to 1250 degrees Celsius.

Raw materials, molding, drying, firing

Raw materials for ceramic tiles are quite widespread. This is one of the reasons for the relatively low price of the material. The product itself is a mixture of clay (to give the material plasticity) with the addition of quartz sand (a non-plastic element gives structural strength) and carbonate or feldspar (provides flux). The glaze is formed by sand, kaolin, pre-prepared glass (frit), and oxidized pigments to impart color. All materials are carefully crushed and mixed into a homogeneous mass for molding. Depending on the type of tile being produced, the mixture can be presented either as a powder with 4-7% moisture content, or as a plastic clay with 15-20% water content. In the first case, the tiles are formed by pressing, using various presses, at a pressure of up to 300 kg/cm ² and higher. In the second case, the tile passes through an extruder into the desired shape. After molding, the tiles are first dried, removing most of the moisture, and then fired (in the case of unglazed tiles) in constantly heated kilns at the temperatures indicated above. During firing, physical and chemical reactions occur, which give the tile, depending on its purpose, such technical characteristics as density, mechanical stability and physico-chemical inertness.

Density and porosity of ceramic tiles

The density and porosity of the tile depends on the firing cycle and the raw materials used. What porosity is will be discussed below. This quality is determined by the amount of moisture absorbed and is a very important parameter that affects other characteristics of the tile. It should be noted that the changes that cause the high density of the ceramic mass, as well as the low water absorption of the tiles, are associated with the formation of an integral stage of melting at high temperatures of the ceramic mass, which hardens upon cooling, forming a vitrified structure. This process is accompanied by shrinkage of the tiles in size, i.e. After firing, the tile decreases in size. This property entails a certain degree of heterogeneity of dimensional characteristics. The greater the shrinkage, the less the degree of water absorption.

Double and single firing

In the case of glazed tiles, after drying, it is possible to use two technological approaches: the double-firing method and the single-firing method. In the first case, the dried tile is fired, then the glaze and decors are applied to the resulting body, the tile is subjected to a second firing, the main purpose of which is to fix the glaze. In the case of a single firing, the glaze is applied to the dried workpiece, and the glaze and ceramic mass are fired together, at the same time the tile is fired and the glaze is stabilized.

Sorting

At this stage of the production cycle, tiles are sorted, defective ones are destroyed, higher quality is separated from lower quality, and tiles are separated into groups based on size and tone.

Types of ceramic tiles

A brief summary of the technological cycle for the production of floor and wall ceramic tiles leads to the following observations:

1. Ceramic tiles, like all ceramic materials, are fired at high temperatures, which makes the stable mass stable and inert to the harmful physical and chemical influences of the environment. On the other hand, ceramic tiles have a fragile structure. Ceramic tiles do not undergo plastic changes (i.e., they do not bend); when they reach their elasticity limit, they break. The tiles have a low degree of elasticity and therefore are not resistant to mechanical stress. It must be emphasized that this quality of ceramic tiles, which is characteristic of many other materials (for example, porcelain, glass, etc.), is not a defect. It’s just that this property of the material must be taken into account during application.

2. It is possible to produce ceramic tiles with different technological cycles (single and double firing), using different raw materials (white or red mass), different technological approaches for each individual stage of production (compression molding or extrusion), production with different operating parameters of the equipment. Each choice, each parameter corresponds to a specific type of product (see figure), with correspondingly different characteristics. These differences are of great importance, and if you do not take them into account when choosing tiles, it can cause problems.

The fact that the designer, builder, or consumer can choose from a wide range of products (see table) is not always an advantage. The various defects that form on tiles are usually not caused by the choice of a bad tile, but by a bad choice of tiles . It is very important to make the right choice; for this you need to carefully study the material itself. In particular, when choosing a tile, it is necessary to take into account its technical characteristics, but also not to forget about the aesthetic and decorative selection criteria.