Being an excellent thermal shock resistant and fluxing agent, talc is widely used in ceramics industry. Talc improves the mechanical and optical properties of floor and wall tiles, and allow producers to cut energy costs and CO2 emission.
Talc is also used as a matting agent in floor tiles where it improve whiteness without affecting expansion, abrasion and stain resistance. Used in combination with calcined alumina, It delivers excellent satin finish glazes with good fusibility and low thermal expansion, improving glaze body fit and reducing pinholes.
Talc reduces gloss gradually so it is a more effective matting agent and less harsh than alumina.
Floor & Wall Tiles :
When used in combination with feldspar, talc brings magnesium oxide to the ceramic flux which:
- lowers fusion temperature
- speeds up the vitrification process
- improves composition viscosity
- increases surface tension
- stabilizes thermal expansion – important for large format tiles
This means substantial savings in terms of energy and CO2emissions through reduced firing cycle and decreased firing temperature.
Frits, Glazes & Engobes :
In frit composition, talc with a very low iron content provides magnesium in the frit which improves thermal expansion & fusion; and gives good melting behavior.
In fritless glazes such as sanitaryware glazes, talc enable manufacturers to lower barium carbonate and zinc oxide levels, thus
- enhancing whiteness
- improving acid resistance
- reducing pinholes and formulation costs
In wall tile engobes, talc with a very low iron content provides zirconium silicate savings. Combined with magnesite and kaolin, talc improves the efficiency of refractory engobes used to protect ceramic kiln rollers.
Glaze body fit:
Talc controls moisture expansion of the tile body and stabilizes thermal expansion. These two phenomena combined diminish strains between the body and the glaze during cooling inside the kiln, improving body-glaze fit.
In sanitaryware talc allows manufacturers to reduce barium carbonate and zinc oxide level improving glaze body fit at a lower formulation cost.
Automotive cordierite ceramics :
Talc is the key raw material for automotive cordierite where it is used to produce the ceramic honeycomb component in catalyst supports and diesel particulate filters (DPF). Talc has a beneficial effect during body preparation, extrusion and firing, as well as on the properties of the final component.
Talc is the prime raw material for steatites used in electrical and mechanical applications where it makes up between 65% and 90% of the body.
Talc decomposes into enstatite which possesses electro-insulating properties for high voltage, high frequency applications.
Steatite demonstrates excellent mechanical properties and good shock and abrasion resistance, making it useful in grinding media.
Large format & thin tiles :
The principal problems encountered during the manufacturing of large format tiles are evenness and pyroplastic distortion during firing. Talc stabilizes linear thermal expansion and moisture expansion, reducing strain between the glaze and the body during cooling inside the kiln, improving expansion linearity. When thermal expansion is evenly distributed in the tile body, large format tiles maintain a flat, even surface.
The principal problem with thin tiles is their mechanical resistance. Talc provides mechanical strength by increasing tile density and by reducing closed density. Talc, being an fluxing agent, also reduces water absorption.
Talc improves the mechanical and optical properties of sanitaryware bodies and glazes. In sanitaryware bodies talcs act as silica mineralizers which:
- improve vitrification, meaning fewer losses during second firing
- reinforce mechanical properties of large components such as shower trays.
Talcs also make ideal dusting agents for demolding.
In low temperature soft earthenware, talc:
- improves plasticity in the ram process
- improves glaze body fit
- reduces cracks during cool-down in very fast firing processes
In low temperature porcelain pottery dinnerware, talc:
- improves vitrification
- reduces firing cycles
- increases mechanical properties
Talc with a low iron content should be used for this application to ensure whiteness after firing.