Ceramic & Porcelain Glossary

There are a number of terms that you may hear or read when shopping for or learning about ceramic and porcelain tile. Here's a list of some of the most common words, and their definitions, that should make the entire process easier for you.

ASTM - American Society for Testing & Materials. The most common system rates ceramic tile abrasion resistance or the overall durability of the tile. Other ratings might include: scratch resistance, moisture absorption, chemical resistance and breaking strength.

Biocuttura Tile (also known as Double Fired) - Tiles that are first fired after the green tile is dried and then fired again after the glaze is applied.

Bisque -The body of the tile, or largest layer, is called the bisque. The top layer is called the glaze.

Bullnose - A ceramic floor tile trim that has one rounded finished edge on the tile to give a nice finishing touch. Sometimes it is also used as a substitute for cove base.

Ceramic - Ceramic tiles are created from natural products extracted from the earth that are shaped into tiles and then fired in kilns at extremely high temperatures.

CBU - Cement Backer Unit. The backer board used in the thin set method of installing ceramic or porcelain tile. The CBU provides a supportive and water resistant layer between the porous substrate and the mortar and tile applied on top of it.

Classes 1-5 - System of measuring strength of ceramic and porcelain tile.
Class 1: no foot traffic. These tiles are suggested for interior wall applications only and not for the floor.
Class 2: light traffic. These tiles are suggested for interior wall applications and for residential bathroom flooring only.
Class 3: light to moderate traffic. These tiles can be used for residential floor and wall applications including bathrooms, kitchens, foyers, dining rooms and family rooms. They're a good all-around performer.
Class 4: moderate to heavy traffic. These tiles are recommended for residential, medium commercial and light industrial floor and wall applications including shopping malls, offices, restaurant dining rooms, showrooms and hallways.
Class 5: heavy/extra heavy traffic. These tiles can be installed anywhere. They will hold up in floor and wall applications at airports, supermarkets and subways.

COF - Coefficient of Friction. The measure that is the basis for the Slip Resistance measure of ceramic and porcelain tile. The higher the COF the more slip resistant the tile. This is important when selecting a floor tile for areas that get wet, such as your shower or bathroom floor.

Corner Bullnose - A ceramic floor tile trim that has two rounded finished edges on the tile to be used to complete a corner.

Extrusion - Extruded tiles are formed by forcing the clay material through a mold for the desired shape versus pressing the tile.

Field Tile - The most prominent tile throughout a pattern involving different types of tile.

Firing - The process of hardening tile with heat. Ceramic tiles are fired in the kiln at temperatures around 2000 degrees Fahrenheit.

Frit - A glass derivative used in the glazing of ceramic and porcelain tile.

Glazed - Glazed ceramic tiles are coated with glass-forming minerals and ceramic stains. Typically, they have a matte, semi-gloss or high-gloss finish. They can offer better stain and moisture resistance than unglazed tile. Glazed tiles have a hard non-porous, impermeable surface after firing.

Glazing - The process of applying glaze to a tile. Glazing liquid is prepared from a glass derivative called frit and colored dyes. The glaze is applied by either a high-pressure spray or is poured directly onto the tile.

Green Tiles - Clay that has been pressed or formed into a tile shape, but have not yet been fired.

Grout - A type of cement that is used to fill the space and provide support in tile joints. There are two types of grout commonly used in home installations; Portland cement based, and epoxy based. Both of these grout compounds may have sand added to provide additional strength to the tile joint. Pigment is added to the cement at the job site when the grout is mixed.

Impervious Tiles - Tiles that have less than .5% moisture absorption. These tiles are frost proof and can be used in exterior areas or on the outside of building facades.

Moisture Absorption - As the density of the tile increases, the amount of moisture that tile can absorb becomes less. Tile density and moisture absorption have an indirect relationship to each other. What this means is that as the density of the tile increases the moisture absorption rate becomes less. Tile density and moisture absorption is important for you to understand when selecting tile for different applications.

Monocuttura Tile - Glazed tiles that are fired only once. This firing occurs after the glaze.

Mosaics - Tile size 2" x 2" and smaller are usually referred to as mosaics and are often used with different colors to create a pattern or decorative inset. Some of these smaller tiles also come in different shapes, such as hexagon.

Nominal Size - The size a tile was before firing. During the firing process, ceramic tile will shrink, on average, by about 10% in size. For example a 12" by 12" floor tile can measure 11-7/8 inches square.

Non-Vitreous Tiles - Tiles that absorb 7% or more moisture. They are suited for indoor use only.

Porcelain - Porcelain tile is made up of 50% feldspar and is fired at a much higher temperature than regular ceramic tile, making porcelain tile much harder and more dense than other tile products. Compared to ceramic, porcelain is more resistant to scratches, can withstand temperature extremes, is stain resitant, and has a very low water absorption rating.

Pressing - The process of pressing or forming clay into a tile shape. These pressed tiles are called green tiles because they have not yet been fired.

Sanded Grout - Grout that contains sand. Sanded grout is recommended for tile joints 1/8th of an inch and larger.

Sanitary Cove Base - A ceramic floor tile trim that has a rounded finished top like a bullnose to cover up the body of the tile.

Semi-Vitreous Tiles - Tiles that absorb from 3% to 7% moisture. They are applicable for indoor use only.

Shade Variation - Shade variation is inherent in all fired ceramic products and certain tiles will show greater variation within their dye lots. Shade variation is usually listed on the back label of each sample with a low, moderate, high or random rating.
Low: consistent shade and texture.
Moderate: moderate shade and texture variation.
High: high shade and texture variation.
Random: very high shade and texture variation.

Substrate - The tile foundation upon which the tile is set. Common materials used as tile substrates in home installations include concrete, plywood, and drywall.

Thickset - A technique for setting tile that is seldom used today. In this method, a thick layer of mortar was applied to a waterproofed and steel reinforced substrate. The thickset method is effective, but it's an involved and labor-intensive process.

Thinset - The most common technique for setting tile.  In this method, the tile is adhered directly onto a backer board that is nailed to a plywood or concrete substrate using a much thinner layer of mortar.

Through Body - Unglazed tiles that are a solid color all the way through and do not have a top layer of glaze are often referred to as through-body construction. (See Unglazed.)

Tile Density - This measure is tied to water absorption. As the density of the tile increases, the amount of moisture that tile can absorb becomes less. Tile density and moisture absorption is important for you to understand when selecting tile for different applications.

Unglazed - Unglazed tiles are a solid color all the way through and do not have a top layer of glaze. They have no additional surface applications and are typically more dense and durable than glazed tile, making them more suitable for interior and exterior applications. Unglazed tiles do have good slip resistance, but they do require sealing to help prevent staining.

Unsanded Grout - Grout that does not contain sand. Unsanded grout is typically used in joints that are smaller than 1/8th of an inch.

Vitreous Tiles - Tiles that absorb less that 3% moisture. They are referred to as frost resistant tiles but cannot be used in exterior areas where freeze- thaw conditions could cause tile cracking.