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The relative hardness of glazed tile is an important issue that should be addressed when selecting a tile. The test is performed by scratching the surface of the tile with different minerals and subjectively assigning a MOH’s Scale Hardness” number to the glaze. The softest mineral used is talc (“1”rating), the hardest is a diamond (“10”rating). Other minerals of varying hardness provide MOH’s Scale Hardness values of 5 to 7, which are suitable for most residential floor applications. A value of 7 or greater is normally recommended for commercial applications.


Ceramic tiles used on floors and walls must be able to withstand the expected load-bearing capacity of various installations. The tile industry uses ASTM C648-04 to determine the strength and durability of the tile. A force is applied to an unsupported portion of the tile specimen until breakage occurs. The ultimate breaking strength is then recorded in pounds. Final selection of the tile should be based upon the breaking strength and the appropriate installation method. Tile integrity is critically dependent upon proper installation.


Chemical resistance is measured using ASTM C650-04. A tile sample is placed in continuous contact with a variety of chemicals for 24 hours, rinsing the surface and then examining the surface for visible variation.


The durability of glazed tile is measured, subjectively, by observing the visible surface abrasion of the tile when subjected to the ASTM C1027-99 testing procedure. Evaluates glazed tile recommended for floor applications using this test method, which includes the following classification system:

Class Zero Not recommended for use on floors

Class One Light Traffic – Residential floor coverings in areas subject to soft-soled footwear or

(Light normal footwear traffic, without scratching dirt (i.e. domestic bathrooms and bedrooms

Residential) without exterior access.)

Class Two Light to Medium Traffic – Residential floor coverings in areas subject to soft-soled

(Residential) footwear or normal footwear traffic with small amounts of scratching dirt (i.e. rooms in

the living areas of homes except kitchens, entrances and other areas that may be

subjected to high usage).

Class Three Medium to Heavy Traffic – Residential or light commercial may withstand normal

(Heavy footwear and regular traffic, with some dirt and/or other abrasives present in limited

Residential quantities. Tile in this class may be used in light commercial installations with limited

or Light foot traffic and with no direct access to the outside. Examples may include residential

Commercial) kitchens and hallways with limited traffic from the outside.

Class Four Heavy Traffic – Residential and commercial floor coverings subjected to considerable

traffic and scratching dirt (i.e. entrances, workrooms, inns, exhibition halls, and sales

rooms, as well as other rooms in public and private buildings). Floors should be

adequately protected against scratching dirt at the entrances to buildings by either floor

mats or some other footwear cleaning device.

Class Five Heavy Traffic – Heavy commercial floor coverings subject to heavy traffic with very

(Heavy abrasive soil.


Water Absorption

This symbol represents the quantity of water that a single tile can absorb expressed as a percentage of the dry weight of the tile. High water absorption corresponds to a highly porous structure. Compact or vitrified structure will feature low water absorption.

Percentage Classification Products

0-0.5% Impervious Porcelain tiles, frost proof

0.5-3% Vitreous Red and White body floor tiles, frost proof

3-7% Semi-Vitreous Non-frost proof red and white body wall and floor tiles

>7% Non-Vitreous Monoporosa floor and wall tile, double fire wall tiles

Shade Variation

Source: Ceramic Tile Distributors Association

The color shade or shades of all tile varies in some degree from piece to piece and from production run to run. At least several pieces from the same production should be reviewed whenever possible to determine acceptable color shade variations. Any questions or concerns about your tile selection should be clarified prior to installation.

V1 Uniform Minimal to no differences among pieces from the same production run.

V2 Slight Distinguishable differences in texture and/or pattern within similar


V3 Moderate While the color present in a single piece of tile will be indicative of the

colors to be expected on other tiles, the amount of colors on each piece

may vary significantly.

V4 Random Random color variation from tile to tile, so that one tile may have totally

different colors from that on other tiles. Thus, the final installation will

be unique.

PEI Rating

Source: The Porcelain Enamel Institute

The PEI Rating of I, II, III, IV or V defines the wear and durability of a tile’s glazed surface.

Class 0 PEI I Decorative

Class 1 PEI I Residential and commercial wall and barefoot traffic

Class 2 PEI II Wall and residential bath floor, soft-soled traffic

Class 3 PEI III All residential and light commercial floors

Class 4 PEI IV Medium commercial and light industrial, institutional, moderate soiling

Class 5 PEI V Heavy and extra-heavy traffic, abrasive dirt

Frost Resistance: Yes/No

Defines whether the tile is frost resistant. Product manufactured for use where freeze and thaw conditions exit.

Terms & Definitions

Body/Bisque Refer to the structural portion of a ceramic product & to the material of Mixture from which it is made.

Dot-Mounted Tile mounted into units or sheets using PVC material as a connector. Bonding the tiles together at the edges not covering the back.

Glaze A glass-like coating applied to the ceramic body that is then fired. Also  Refers to the material or mixture from which such coating is made.

Glaze Tile A fused, impervious facial finish composed of ceramic material fused to The body of the tile which may be nonvitreous, semivitreous, vitreous & Impervious.

Gloss The term used for a tile which has a high shine to its surface. Can Generally see your reflection on the tile surface.

Impervious Water absorption of less than 0.5%

Matte A term used for a tile with a soft finish as opposed to a high-gloss finish. A matte finish is less likely to scratch than a high-gloss or semi-gloss tile.

Monocottura Method of producing tile by single firing in which body & glaze are fired Simultaneously in kilns at temperatures greater than 1200 degrees.

Nominal Sizes Approximate facial size or thickness of tile for general references Expressed in inches or fractions of an inch.

Non-Slip Tile Tile with greater non-slip characteristics due to an abrasive ad mixture, Abrasive particles, grooves or patterns in surface or because of natural Non-skid surface characteristics.

Nonvitreous Water absorption of greater than 7%.

Semi-Vitreous Water absorption between 3% and 7%.

Sheet-Mounted Tile assembled into units or sheets, either back-mounted or face-mounted  And bonded by suitable material to facilitate handling. Back-mounted has Perforated paper, fiber mesh, resin or other suitable material permanently  Attached to the back and/or edges so that a portion of the back of each Tile is exposed to the bond coat. Face-mounted has paper applied to the Face of the tile, usually by water-soluble adhesive so it is easily removed Prior to grouting of the joints.

Unglazed Hard, dense tile of uniform composition throughout, deriving color &  Texture from the materials of which the body is made.

Vitreous Water absorption between 0.5% and 3%.