Porcelain Tiles
Not all that long ago, the answer to the question “should porcelain be sealed?” was a resounding “no”. The only important questions then related to correct installation and maintenance. These days however, it is not quite that straight forward.
Porcelain was first pioneered in Italy by a small select group of companies all working to a defined set of high standards. Porcelain is made from a more pure blend of high quality clay than used in “normal” ceramic production, utilizing a higher percentage of Kaolin clays. These have high silica content and result in materials that have all of the characteristics of silica itself once fired, namely low water absorption, high chemical resistance, high abrasion resistance, and good overall hardness.
The pioneers of this technology recognized this high performance and marketed it accordingly with porcelain becoming the benchmark. One of the most accessible technical features used by the marketers to highlight this high performance aspect was water absorption. The European standards (Tolerances ISO UNE EN ISO 10.545-3) set water absorption at less than 0.5%. In many cases the European manufacturers bettered this impressive standard with common water absorption being less than 0.1%.
So, with such low water absorption and with the clay being milled and spray dried to such a small particle size before pressing and then firing to over 1200 degrees Celsius, the resulting porcelain did not need sealing.
Since then however, with then advent of different market requirements and the proliferation of porcelain manufacturers worldwide, “porcelain” can no longer be assumed to meet the same original technical and performance criteria of the early pioneers. There are now many types of porcelain, especially polished, manufactured in different countries, to different standards. The fact is that many of these porcelains have a rate of water absorption higher than the original standard and so they do absorb liquids and some have a tendency to stain when grouted with coloured, polymer-modified grouts. Consequently they can benefit from sealing. To find out whether a porcelain will benefit from sealing do a simple water test. If, after several minutes, water is absorbed, then the tile can stain and will benefit from sealing with a good quality, penetrating type sealer.
Another very common problem at the moment is that some porcelain tiles become very dirty once in use. However this does not necessarily mean the tile needs sealing, indeed this may still occur with some tiles even if adequately sealed. The main reason for sealing porcelain is to stop it absorbing things that would eventually stain. However as these sealers are penetrating they do not offer any protection to the actual surface and it is surface soiling that is the typical culprit in most cases. Today, porcelain is produced with many different surface textures, often in an attempt to mimic the surface textures of natural stone; many of them (created by the use of plastic dies to press the tile body before firing) result in a surface that has a many small “pockets” that can have a tendency to “grab” dirt. It is these surface textures that are more often than not the reason for the problem of surface soling.
A common complaint is that when porcelain is used in a car showroom or garage, car tyre marks are very easily transferred on to the tile but not easily removed. The client then assumes that a sealer will remedy the problem. However in most cases it is the very fine surface texture, characteristic of most porcelain that is abrading the tyre and lodging the rubber particles in the very small fine pores of the tile. It is very often further complicated by the presence of small amounts of grout haze left on the tile surface after installation. The solution to this problem is to clean and maintain the porcelain correctly rather than apply a sealer. This type of porcelain cannot be maintained by wet mopping alone. The characteristic microscopic textured surface requires periodic cleaning with a heavy duty alkaline cleaner and an abrasive nylon-scrubbing pad or a deck brush.
So the answer to the question “should porcelain be sealed?” is no longer a blanket “no” perhaps a better answer would be “It depends on the porcelain”.
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