Slippery Rock Gazette

Bob Murrell 

Stone Restoration

Photos provided by Bob Murrell

For many years I have received calls from customers who start the conversation by saying, “I have a ceramic tile that needs improvement.”             

Of course I respond by saying, “What type of ceramic tile?” The answer is most always of course, “You know, ceramic tile.”

Not being a mind reader, I don’t know what type of ceramic tile they are talking about until they can give me more information. The point they are missing is that there are many types of ceramic tile, which have many different properties and associated potential maintenance issues.

The word ceramic basically means earth or soil. Ceramics are made from clays, then molded or formed under pressure. Once formed, they are then fired at high temperatures to permanently harden the tile.   

These clays can be left as is, refined by removing impurities, or even have certain substances added to improve specific properties, such as strength, color, or even slip resistance.   

Some examples are: Mexican pavers, terra cotta, brick pavers, quarry tiles, monocottura (glazed and fired one time) glazed tiles, and of course, the porcelain tiles. All are a type of ceramic tile and yet all have very different properties.

The Mexican tiles or terra cotta type tiles are the oldest form and the most simple. These tiles are made from naturally occurring clays with little or no refinement and roughly formed into a tile shape, sometimes in wooden molds. They are then fired in simple kilns. 

Their beautiful red colors are a result of high iron content in the clay. These tiles are fairly porous and would normally require sealing and/or waxing to protect from staining. The dimensional tolerances are typically somewhat inconsistent, but this should be no surprise in a handmade product.   

The next group is the quarry tiles. The clay in this group is more refined by removing impurities and in some cases other materials are added to improve strength and color. Quarry tiles are normally formed by the extrusion method (squeezed like toothpaste) which involves much more pressure than the Mexican tile group. The tiles are then cut to size. 

Unfortunately, to extrude the clay, more water must be added to the clay which results in some deformation while the tile is being fired. This makes it more difficult to control the dimensions of the tiles as well. The use of quarry tiles is common at restaurants and commercial kitchens.

Because the above two categories of tiles are “dimensionally challenged,” the use of wide grout lines is most always implemented to compensate for the irregular sizes.

The dimensional accuracy of certain ceramics was greatly improved with a newer manufacturing process called the dust pressed method. 

Tiles from this process are generally called pavers and are much more dimensionally accurate. This is because the clays used can be more refined, dried to less water content, and in the case of porcelains, are pressed with hundreds of tons of pressure to remove most all voids between the clay particles. 

The tile is then fired at much higher temperatures. This higher tech manufacturing process results in a tile that is much more compact, harder, has less deviation in the dimensional tolerances, and can even be naturally polished. 

Porcelains are the favorite choice for most commercial applications because of their durability. You see, porcelains can be harder than many granites based on the Mohs hardness scale. Keep in mind that very hard minerals can be added to the clay.

Commercial bathrooms are almost always favorites of the 2´ x 2˝ porcelain tile. Building owners and service contractors often desire these restroom floors have more shine, so they will try waxing, but it doesn’t stick and fails quickly. There is a two-step powder system available that will impart a permanent shine which will brighten the tiles and make them easier to keep clean.

Lobbies and upscale department store showrooms use polished and honed porcelains to accentuate. The Italians, and others like popular US porcelain manufacturers, have been able to incorporate the look of stone, wood and other substances into their porcelain tiles.

Another dust pressed tile is the monocottura tile. This tile is formed by the dust pressed method, then a glaze is added before firing. Glazes are a specially formulated glass. The tile or biscuit can be painted and the glaze can be colored or not. 

Generally, biscuits that are porous and reddish in color are sealed and protected by the glaze. Glazed tiles are typically used for residential situations and commercial vertical surfaces as the glaze will not stand up to heavy foot traffic.   

Now that we have discussed some of the main varieties of ceramic tiles used today, we can focus on the maintenance procedures and options. All ceramic installations have grout. Mexican and quarry tiles normally have larger grout lines to compensate for their lack of dimensional tolerances. Porcelains would normally have very thin (1/16˝-1/8˝ max) grout lines like cut marble or granite tiles. 

Mexican terra cotta tiles should be either impregnated and sealed, or waxed. Quarry tiles, because of their extrusion manufacturing process, tend to have a skin that develops on the surface. When that wears through, they become more porous and should be impregnated to help prevent foreign contaminant penetration.

All grout lines, with the exception of epoxy grout, need protection from staining. Water-based or solvent-based impregnators are normally adequate. As we have previously discussed, solvents penetrate better and therefore have the potential of providing and longer life. In any case, be sure that your impregnator is oleophobic (resists oil and grease) where required.  

Normally daily maintenance is accomplished by first dust mopping and then by using a quality no-rinse pH neutral cleaner. When installations become extremely soiled or greasy, the use of alkaline cleaners is necessary to remove these contaminants. Using warm water helps the efficacy of most all cleaning operations. 

Acidic cleaners can be used when grout lines are still discolored after cleaning with alkaline cleaners. Acids will exfoliate (remove the top layer) the grout and therefore should be used only when necessary, and then sparingly, to avoid attacking the integrity of the grout. 

Ask for a spare tile to confirm the type of ceramic tile. Mexican tiles will look like dried red clay or mud on the back. Quarry tiles normally have extrusion lines on the back. Both porcelains and glazed tiles typically have mold imprints on the back. As always, rely on your supplier for quality products and support.

Bob Murrell has worked as a supplier of products and technical support to the natural stone industry for over 35 years. He has written numerous articles for various trade publications and has also trained thousands of contractors over the last 25 years.