Clay and Stone Maintenance

July 12, 2004
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Clay and natural stone floors are sometimes thought of as being in the same floor-covering category. This is an easy assumption to make: both categories have classifications that are solid, very hard and durable; they are sold in tiles, pavers and other geometrical shapes; and they possess similar maintenance procedures. If they have all these common characteristics, why should they be in different categories?

Clay Floor Coverings
Clay floor coverings are manufactured using an earthy material that is flexible when moist and becomes very hard when fired in kilns at extremely high temperatures. They are composed mainly of fine particles of silicates and other minerals, and are used for the manufacture of ceramic, porcelain, quarry, brick and terra cotta. Most clay-type floor coverings are extremely durable and can withstand heat and harsh chemicals.

Various clays and minerals are mixed together to produce the clay body, or bisque. The density determines the strength of the bisque. The density is ascertained by examining the number of air pockets found in the bisque. The strongest bisques, those suited for heavy commercial environments, have the smallest and least number of air pockets.

The density also identifies the level of water the tile can absorb (Chart 1) and if the tile is suitable for use outdoors.

Stone Floor Coverings
Stone floor coverings are created naturally by forces of nature and are geologically classified as igneous, metamorphic or sedimentary rocks.

Igneous rocks are rocks formed by the hardening and crystallization of molten material that originates deep within the earth.

Sedimentary rocks form from sediments of plant and animal remains, as well as fragments of older rocks that are compressed into a hard mass by pressure.

Metamorphic rocks form when heat and pressure increase as the rock moves through its natural cycle. Metamorphism is what causes the calcite in limestone to re-crystallize into marble, the grains in quartz-rich sandstone to grow together to form quartzite, and sedimentary shale to harden and form slate.

Stone floor coverings are quarried from geological deposits. Large slabs are cut and extracted, from which smaller tiles are then cut. They in turn are shipped to the location for installation. True, there are terrazzo and agglomerate floor coverings that are poured on-site or manufactured, but the primary component of these floor coverings is a minimum of 70 percent natural stone chips (generally marble or granite) in a cement or resin binder. Because the majority of these floors' composition is natural stone, they are classified in the natural stone category of floor coverings. Terrazzo and agglomerates are commonly found in high-traffic areas such as transportation and school environments.

The natural stone category of floor coverings is probably the most extensive of all categories, having 10 major classifications (granite, quartzite, serpentine, marble, limestone, travertine, slate, sandstone, terrazzo and agglomerate). There are literally thousands of different variations within these classifications. The natural beauty of the stone floor produces an air of elegance, one reason why they are generally found in lobbies and entryways, as well as other formal areas.

Grout: The Common Denominator
Given that these two categories are completely different in composition and makeup, they do have one thing in common: grout.

Grout is a thin mortar used to fill the empty spaces between the tiles. These spaces vary; they can be less than 1/8 inch or as much as 1 inch. Because grout maintenance is an important part of floor care, it is important to understand the different classifications.

Sanded grout is the most common type of grout for applications of spaces wider than 1/8 inch. Primarily composed of Portland cement, sand and water, it's very porous and absorbent. Because of this, seals are required for the best results.

Non-sanded grout is used when the spaces are less than 1/8 inch. This type of grout is commonly called "wall grout." This is particularly true of natural stone tiles because of their susceptibility to scratching by the sand crystals. Very seldom is non-sanded grout used on floor tiles.

Epoxy grouts are waterless two-part systems consisting of epoxy resins and a catalyst or hardener. The two parts are mixed on-site prior to use. These grouts are smooth in appearance and are very resistant to stains and mildew.

There are many types of latex additives that are mixed with both sanded and non-sanded grout. These additives help reduce or prevent water absorption into the grout. Sometimes latex additives are added as powders at the factory.

Maintenance of Grout
The properties of grout impact floor maintenance regardless of whether the floor covering is stone or clay. Because grout lines are generally, but not always, lower than the tiles and water seeks the path of least resistance, soils from daily traffic and cleaning find their way to the grout. This is compounded when sanded grout is used because of the natural porosity characteristics of the material.

Sanded grout is porous. As soil collects in these pores the grout lines turn dark. Even when sanded grout is sealed or when using latex additives, the same situation can occur; it will just be a little easier to clean. When floor sealants or finishes are used it can really complicate the condition. When the floor is stripped and refinished, the stripping solution will carry the emulsified seal/finish deep into the pores, making it difficult to remove.

Initial Maintenance
Initial maintenance can be easy if the proper care has been taken during the installation process. Wiping up excess residue with a sponge and fresh water or cleaning solution during the installation removes it before it dries. If this process is not done or done poorly, the results can be extremely difficult for the floor maintenance technician who comes in later to perform the initial maintenance. This is especially true of latex additives. These can be extremely difficult to remove, particularly when on a textured surface.

Generally, installation jobs are done very professionally and, in most situations, the installation company will either use additives in the grout or seal the grout with penetrating or impregnating sealants after installation.

The initial maintenance for this scenario is a medium-to-heavy scrub and rinse in conjunction with neutral cleaner, or all-purpose cleaner and an appropriate pad or brush.

If the grout has not been sealed, the technician may have to apply it. There are many brands to choose from and they can be solvent or aqueous; consult the local stone and ceramic tile supplier for the best solution for your application.

Daily/Routine Maintenance
The daily/routine maintenance will be predicated by the environmental conditions the stone or clay floors are exposed to. Generally, stone floors occupy lobbies and halls and therefore can be swept and mopped with neutral cleaner or specialized cleaners on a regular basis. Clay-type floors are also used in these areas and are treated the same.

Clay floor coverings are also found in more function areas, such as restrooms and kitchens. When these conditions occur, the daily/routine maintenance will be pretty much the same with the exception of the cleaning chemicals used, e.g. degreasers in the kitchen and sanitizers in the restrooms.

Remember, water seeks the path of least resistance and will deposit soil at the lowest point, the grout. When mopping tile floors, stone or clay, it is important to remove as much cleaning solution as possible from the surface of the grout. This can be achieved by following the mopping process with a damp mop. Damp mopping requires wringing out as much solution or water out of the mop head as possible. The mop fiber will then absorb more liquid from the low-lying areas.

Periodic Maintenance
Over time the grout will become soiled. Periodic maintenance should be scheduled to keep this condition in check. The common service procedure will be the scrub and rinse. The soiling condition will dictate the aggressiveness of the scrub, while the environment and traffic conditions will dictate the frequency. Keeping the soil in the grout at a low level extends the time between salvage/restorative maintenance procedures.

Machine scrubbing with a cleaning solution and abrasive pads or brushes will loosen the soil and bring it to the surface for removal. The scrubbing machine can be rotary or cylindrical. Brushes tend to work better than pads because of the irregularity of the grout surface.

Extract the contaminated solution using a wet vacuum with floor squeegee or wand attachment, then rinse the floor with clean water. In heavily soiled environments like kitchens and restrooms it may be necessary to apply an ample amount of clean water to the floor and extract it with the wet vacuum before the final rinse.

Salvage/Restorative Maintenance
When salvage restorative maintenance is in order, the service becomes more complex because you will be incorporating grout cleaning with floor cleaning. Diamond abrasives may be used on the stone floor coverings and harsh chemicals - alkaline or acidic - may be used on the clay floors in tandem with abrasive pads. Regardless of the service procedure used on the floor covering, it is the perfect opportunity to clean up the grout.

When soil becomes too deeply embedded in the grout, something has to be done to remove it. Concentrated alkaline and acidic cleaners can be used to remove the bulk of the soil, but there will always be some residual soil. As you will not be able to remove it, it may become necessary to remove a minute portion of the surface of the grout to a point just below the soil. This can be accomplished with the help of a grout saw. The grout saw is designed to abrade away a bit of the grout to expose fresh grout below. Be careful when using this tool as you can sometimes go too far and expose the spacers below.

Once the grout has been totally cleaned, thoroughly rinsed and completely dried, penetrating or impregnating seals can be re-applied. In the case of stone floors, powder polishing or crystallization procedures may be performed to enhance the appearance.

Although clay and stone floors are technically in different floor covering categories, they do have grout in common. The floor maintenance program developed for grout needs to take into consideration factors such as soil, environment and traffic conditions, in addition to the program developed for the stone or clay floor covering. Knowing this in advance can help save hours of labor in the field.

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