Talc in Ceramic Tile Industry

Talc mineral has been used in many applications in Ceramic sector mainly in ceramic tiles, bathroom fixtures, pottery, glaze and dinnerware in bulk quantities in powdered form along with other minerals. Talc acts as a catalyst to improve heat resistance, thermal shock resistance and the strength of the end product. Technical ceramics differ from decorative ceramics in terms of optimized properties with regards to heat resistance, mechanical stability and dimensional stability. Natural mineral talc is a core additive for all types of ceramics as it improves the vitrification process, allowing you to reduce firing temperatures and shorten firing cycles.

The role of talc in the ceramics process depends on its interaction with other minerals in the formulation where it has an influence on the following parameters:

• Porosity (water absorption, etc.)
• Color after firing
• Thermal shock
• Moisture expansion
• Thermal expansion
• Mechanical resistance

• Shrinkage (drying, firing, total shrinkage)
• Talc improves the brightness of super-white porcelain tiles.
• In glazes, when combined with calcined alumina, talc delivers satin finish with good fusibility and low thermal expansion, with reduced pinholes.
• Talc possesses several physical and mechanical properties which uniquely suit ceramics manufacturing
• Talc has high temperature resistance. Hence, it improves thermal shock resistance of ceramics and reduces fractures.
• Talc has low content of iron. Also, Talc has a high content of magnesium. As a result, it imparts great after burning whiteness to ceramics.
• Talc is chemically inert. This to say that it has extremely low reactivity with acids. Subsequently, it makes ceramics acid resistant.
• Pure Talc is hydrophobic in nature. Therefore, it helps to prevent water leakage and seepage in sanitary wares.
• The grinding process of Talc is highly customizable. Thus, it is possible to achieve the desired particle size best suitable for each type of ceramic product rather than one size fits all.

Talc is increasingly being used in the manufacture of artwares, jars, wall and floor tiles. It serves as a non-plastic ceramic material. The addition of talc in suitable proportions in the body of mixtures for porcelain, jars etc. prevents the crazing (cracking) effect on the glazes. The proportion of talc in the ceramic body may go up to 80%. It is valued for its refractoriness and stability, as well as extremely law shrinkage at high temperature. Talc converts into clino-enstatite at about 1300º C. Between 800ºC to 840ºC, the water molecules are driven off and talc dissociates into enstatite and amorphous silica without undergoing any change in shape, the shrinkage being 0.0005 inch only.
In the manufacture of ceramic goods required for the electrical industry, the talc should not contain more than 1.5% FeO and CaO. Some consumers do not regard CaO as having any harmful effect.
Steatite suitable for the manufacture of 'lava' insulators must he dense, compact, uniform and homogeneous in texture, free from any inclusion and parting planes. It should not contain CaO more than 1.5% and Fe2O3; more than 1%. The iron oxide is a colorant and gives the fired shapes an unattractive color. An increase of iron oxide above two per cent decreases the 'Q' value (ratio of reactance to resistance) and increases the dielectric constant. CaO imparts abrasiveness and usually a short vitrification range and sometimes a high firing shrinkage.