Firstly, let’s dispel a little myth; porcelain and ceramic tiles are not different. In fact, both are produced from ceramic, so essentially they are both types of ceramic tile. The English word ceramic is derived from the Greek word ‘keramikos’, which in turn comes from ‘keramos’ or ‘potter’s clay’. The prefix ‘ker’ means heat, fire or burn in Indo-European. As you would expect, words have alternative derivations as many ancient societies - fired loam, earth or clay to produce pottery. Porcelain is one particular type of fired clay, albeit of a more refined quality than those used in ancient times. Kaolin clay (kaolinite) is the main component of porcelain tiles, although other minerals such as feldspar and quartz are present.

BS EN 14411 defines a porcelain tile as a ‘ceramic fully vitrified tile with water absorption of 0.5% or less’. In addition, traditional European porcelain tiles are produced with clays containing as little iron oxide as possible to produce a material as white as feasible.

When clay is fired, it is the degree of vitrification (from latin ‘vitreum’), which determines whether a tile fulfils the requirements of a porcelain tile. Vitrification is the transformation of a material into ‘glass’, which is formed during the high temperature firing phase of tile production. The glassy materials produced fuse together forming a vitreous mass with a reduced number of pores, which is extremely hard and dense.

The properties of porcelain tiles makes them ideally suited to a wide range of applications. They are hard wearing, tough and strong; they absorb extremely low levels of water and are resistant to a wide range of chemicals. These important attributes are essential for external use where they are exposed to extremes of weather (heat, rain, frost) and de-icing chemicals during the winter months. The durability of a porcelain tile helps reduce the environmental impact of floor or wall finishes, as correctly selected and installed tiles will outlast many alternative finishing materials – an important factor to consider in today’s ‘green environment’.

Continuing with the environmental message, porcelain tiles are extremely good conductors of heat, making them an ideal surface for use with energy efficient underfloor heating systems. In addition, their impervious surface allows for easy maintenance, especially in areas where cleanliness is of paramount importance, such as commercial kitchens, hospitals, WC areas and factories.  

As porcelain tiles have extremely low water absorption, there is little opportunity for a tile adhesive to gain a ‘hold’ within the pores. The mechanism for bonding in such systems is largely an adhesive bond, as a mechanical key is not really possible. There may be some slight mechanical action where the tile has a profiled back but essentially an adhesive needs to ‘stick’ to the rear surface of the tile.

In reality, only polymer-modified adhesives will be suitable to bond to this surface, which in general will mean an adhesive classified as C2 in accordance with BS EN 12004. From the Mapei range of products, adhesives such as Mapeker Rapid-set Flex or Keraquick would be appropriate materials for bonding porcelain tiles to a wide range of substrates, both internally and externally. For fixing to walls, Adesilex P9 or Keraflex Maxi S1 will provide the necessary grab and bond strength.

Where weight is an important issue, then an adhesive from the Mapei Ultralite range will provide impressive weight savings. Made with significant quantities of recycled content, these adhesives also add to the environmental ethic of porcelain tiles. The high performance adhesives boast a whole bunch of additional impressive statistics, such as high strength, high grab, flexibility, low dust and low density.

Where porcelain tiles are used in heavy-duty environments, such as shopping malls or leisure complexes, adhesives with higher performance may need to be selected, e.g. Granirapid, Keraquick and Latex Plus.  

In summary, a floor or wall sporting a porcelain tiled finish will give many years of functional, durable and attractive service. It will also benefit the environment, not only in terms of longevity but there are also health benefits: A porcelain tiled finish is easy to clean and keep clean, is non-porous so will not absorb dirt or bacteria, emits extremely low levels of VOC (Volatile Organic Compounds) and, when used as part of a heated floor, conducts heat very effectively.

By Colin Stanyard, Ceramic Product Manager, Mapei UK Ltd

Editor’s note:

Founded in 1937, Mapei is the world-leading manufacturer of adhesives and chemical building products - and a specialist in the production of adhesives and preparation products for the installation of wall and floor coverings. Its extensive product range includes products for the preparation of all types of substrates used in construction:  surface membranes, levelling compounds, primers, waterproofing, ready mixed mortars, special products for the repair of concrete, admixtures for mortar and concrete, adhesives for floor and wall coverings, ceramic tiles, natural stone, soft flooring and wood, grouts and flexible sealants, mortars and binders for the restoration of period buildings, resin flooring, soundproofing systems, protective finishes for exterior walls and special hydraulic binders for screeds.