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TILES
DIFFER NOT ONLY IN TERMS OF APPEARANCE AND THE MANUFACTURING TECHNIQUES
INVOLVED BUT IN TERMS OF THEIR TECHNICAL CHARACTERISTICS.
The characteristics that most distinguish
one type of tile from another and one tile product from another of the
same type are the following:
WATER ABSORPTION
This indicates the level of porosity.
Other important properties are determined by this classification characteristic.
DIMENSION AND APPEARANCE
There may be small variations in the dimension
and appearance of tiles of the same batch, or the tiles may not be completely
flat. These differences and variations are checked in order to ensure
that they do not reach levels that would adversely affect the regularity
of any surface covered by the tiles.
MECHANICAL CHARACTERISTICS
Resistance to loads, such
as the weight of people and furniture to which floor tiles may be subjected
and which they should be able to bear without suffering damage. The
tiles are tested for these mechanical characteristics: resistance to bending
and bending breaking load. In general, the lower water absorption, the
greater the resistance to bending (e.g. it is much greater in vitreous
stoneware, which has a level of water absorption that is lower that 0.5%,
than in "monoporosa" tiles, which have a water absorption level of over
10%).
The bending breaking load
depends not only on the level of water absorption but also on thickness:
the greater the thickness, the higher the breaking load.
SURFACE MECHANICAL CHARACTERISTICS
Resistance to scratches,
scoring, wear from people's feet, and deterioration from the hard objects
that move over the ceramic tile surface. These characteristics are
especially important for floor tiles, on which people walk, and over which
they drag furniture. The surface mechanical characteristics are hardness,
which is an indicator of resistance to scoring, and resistance to abrasion.
This provides an indication of the tendency of the tiles to become worn
(in the case of unglazed tiles) or to change their appearance (glazed
tiles, tested according to the PEI method) because of the above factors.
For Glazed tiles the PEI
method used to measure abrasion resistance, is rated by the following
scale:
PEI 1 Tiles for
areas with light traffic and without abrasive dirt, eg. bathroom
area/barefoot traffic.
PEI 2 Tiles for
areas with light traffic, little abrasive dirt, soft sole shoe
area eg: bathroom/bedroom
PEI 3 Tiles for areas
with medium traffic eg: Residential (domestic only)
PEI 4 Tiles for
areas with medium to heavy traffic eg: Residential, Light Commercial
PEI 5 Tiles for areas
with intense traffic eg: Residential and Commercial.
Surface Hardness is
measured by the Mohs Scale. The Mohs scale is rated from 1 to 10 based
on the increased hardness of the minerals used to scratch them. EN 176
standard requires glazed tiles to have a surface hardness that is not
less than 5. The Mohs Hardness Scale is as follows: 1 - Talc, 2 - Chalk,
3 - Calcite, 4 - Fluorite, 5 - Apatite, 6 - Feldspar, 7 - Quartz, 8 -
Topaz, 9 - Corundum, 10 - Diamond being the hardest. The higher the Mohs
Scale hardness of the tile surface the less the risk that objects and
other materials can scratch and etch it permanently.
CHEMICAL CHARACTERISTICS
Resistance to the corrosive
or staining action of substances that may come into contact with the tile
surface. These chemical characteristics are tested: resistance to
staining, resistance to household chemicals, and resistance to acids and
alkaline.
RESISTANCE TO HUMIDITY AND TEMPERATURE
CHANGES
These consist of resistance
to thermal shocks, resistance to frost, and for glazed tiles, resistance
to cracking. Thermal shocks, such as those to which the ceramic counters
in the kitchen are subjected to when a hot pot is placed on them, and
exposure to frost, to which outside floor and wall tiles are exposed in
cold climates, should not harm resistant tiles. Crazing may be an "obvious"
fault, meaning it is already visible in the tile before they are installed,
or it can be a "hidden" fault, which appears only some time after the
tiles have been installed. In this case, the defect may be due to the
way that they were installed (the mortar were unsuitable or else the mortar
or adhesive have been laid on too thick).
SAFETY CHARACTERISTICS
The main characteristic
is slip resistance. This is fundamental for floor tiles that are to
be used in homes, offices, industrial areas and outdoors.
THE MANUFACTURERS GENERALLY
DISPLAY THE VALUES OF THE DIFFERENT CHARACTERISTICS IN THEIR CATALOGUES.
THESE "TECHNICAL SPECIFCATIONS": FOR THE TILES ARE VERY IMPORTANT
BECAUSE THEY ARE AN IDENTITY CARD FOR THE TILES.
The official Italian laboratory
for ceramic tile testing and certification is the CENTRO CERAMICO via
Martelli, 26 - 40138 BOLOGNA (ITALY)
Standards also set out the
minimum requirements for the different characteristics. In the UNI EN
standards, for each of the eight groups in which the tiles are classified
according to the level of water absorption and the forming method, there
is a specific standard that contains all these requirements, which vary
for each group.
It should be noted that for
certain characteristics, no minimum requirement has been established.
The manufacturer declares the value of the characteristic of the product
and the purchaser has to determine whether the product meets his/her standards.
Two examples of such characteristics
are, for example: resistance to abrasion of glazed tiles. (This
goes from class PEI I, minimum resistance, to class PEI IV, or, with the
new ISO standards, to class PEI V, which is assigned to the most resistant
tiles, resistance to acids and to alkaline of glazed tiles.)
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