The boiling water absorption testing method involves drying the tiles out completely and then boiling them for two hours in water followed by cooling them to room temperature for four hours. The mass of ceramic tiles are weighed both before and after they have been immersed in water to calculate the percentage of water absorption.
The second water absorption testing method is the vacuum method which involves placing the ceramic tiles inside a chamber and then evacuating the air from the chamber. The tiles are then immersed in water. As with the boiling method, the tiles are weighed both before and after water immersion to calculate the apparent porosity, relative density and bulk density.
If the ceramic tiles have low water absorption, this generally means that they have increased strength and durability. Low water absorption means that the tiles have a decreased chance of failure from cyclic salt attack and freeze thaw.
These low water absorption tiles can also be referred to as fully vitrified, impervious and porcelain. Such tiles exhibit water absorption characteristics of less than 0.5 per cent when tested. It is also important to remember that whilst the consumer may view these types of ceramic tiles as superior to other products, it does not guarantee that they are the most suitable for the particular purpose that the consumer has in mind.