Cleaning & Maintenance Management Online

Clean & protect stone without a hitch

September 19, 2010

There are many ways to make money in the cleaning business, and stone cleaning and protection is one of the most profitable.

However, there is a price to pay for that privilege.

One must study the types of stone available in the marketplace and learn the requirements of those stone types. Also, it is essential to learn some information about grout.

There are many stone types that can be used by designers and architects for flooring, wall coverings, bath vanities, shower walls, and counter tops. Limestone, marble, travertine and granite seem to be the most popular choices, but there are many other types of stone to be aware of.

Identification of each type is important to ensure that there are no cleaning problems. Let’s look at several.

Limestone is a calcium-based sedimentary stone that is typically finished by honing — meaning it has a smooth, but dull surface.

It’s fairly absorbent, susceptible to stains from liquids, and sensitive to acids. This includes acid-based beverages and fruits, not just cleaning products.

Acidic cleaning products can etch the limestone’s surface, causing damage to the finish and dull spots that are visible in certain light.

When cleaning, check the stone and the cleaning agents to ensure that there will not be any bad reactions from the products.

Marble is a calcium-based metamorphic stone, also sensitive to acidic products.

Like limestone, marble can absorb liquids into the capillary structure of the stone.

The capillary structure is the area inside the stone that allows liquids to penetrate. The capillaries were created when the stone was geologically formed millions of years ago.

Marble is usually finished by polishing the surface with diamond abrasives to create a glass-like finish with a great reflective shine.

The crystals in the marble’s polished minerals cause the surface to become reflective.

Marble can also be finished by honing or tumbling, giving the marble a distressed appearance. Tumbling removes any sharp edges and gives the stone the appearance of being very old and worn.

Cleaning marble can be challenging because acidic products can etch the stone surface, causing damage and dull spots that are visible in certain light.

Travertine, like limestone, is also a calcium-based sedimentary stone and can be damaged by acidic products.

Many travertine species can be absorbent and liquid spills can cause stains under the surface.

Travertine is usually honed for a finish concept, but the stone contains voids or holes in the surface, and sometimes all the way through the stone.

These voids can be a maintenance headache, as they will be filled with a polyester resin if the travertine is polished or with grout if the travertine is honed.

The grout will fill the voids as the travertine tile is installed.

The fill used in the voids can be removed by heavy traffic, improper installation techniques or by improper cleaning techniques. If the fill is removed, it can cause real problems for the maintenance manager.

The fill will be replaced by soil and it will be difficult to remove from the voids, as they will be lower than the rest of the surface.

An igneous stone of volcanic origin, granite is the hardest of all common building stones.

It has minerals that will not scratch with a steel knife, making granite an excellent selection for countertop surfaces.

Some species of granite, even though extremely hard, can still have a large capillary structure, which will allow liquid penetration.

This can cause the granite to stain if the stone is not properly protected.

Granite can be finished by polishing with diamond abrasives, honed to a flat smooth finish with no shine, or a number of other popular finish types.

Granite can also be flamed to give the surface a very rough texture, which can trap soils and make routine maintenance a nightmare.

Stone maintenance
When maintaining stone, be sure to consider its tendencies absorbent to product.

An easy way to determine if the stone is absorbent is to place some water on the stone and observe it. If the minerals begin to darken in the area the water was placed, it’s absorbent.

If absorbent, care must be exercised in the amount of water used in the cleaning process. Too much water can cause the stone to have some “downstream” issues, such as efflorescence.

Efflorescence is a mineral salt that will appear on the stone tile or along edges of the grout.

Efflorescence comes through the capillary structure of the stone, drawn by the evaporation process. As the moisture evaporates, the mineral deposit is left on the surface.

Wet cleaning with acidic products will remove the surface minerals, but the moisture used in the process will bring more to the surface. Using low-moisture cleaning techniques will minimize the potential of efflorescence.

There are issues with chemical sensitivity on some types of stone.

Most calcium-based stones are sensitive to acids and acid-based cleaning products, so be sure to use neutral or alkaline cleaning agents on these types of stone.

Granite is usually not acid-sensitive, but you should test the surface to see if there is a negative reaction (etching).

The fill in the space between the stone tiles is made up of grout, a cement mixture with color pigment.

A cement mixture hardens though a hydraulic process, not moisture loss. Once the grout hardens and cures, it becomes concrete.

Concrete is extremely absorbent and liquid spills can cause discoloration and stains.

Grout also has a capillary structure from the curing process, making it very porous.

Cleaning concrete is a difficult task in its own right, but the fact that most grout channels are lower than the tile surface gives soils a channel or groove to settle in.

Routine cleaning procedures designed for flat floor surfaces simply do not work in this instance.

Dust mops leave soil in the grout channel and, if we have added dust mop oil to the mop, we will also leave traces of oil in the concrete channel.

Damp mopping also will leave soil behind in the grout joint, leaving behind both protein-based (organic) soils and inorganic soils.

Organic soils are displaced or emulsified with alkaline-based cleaning agents, but inorganic soils are best removed with an acidic cleaning agent.

The acidic agent will not emulsify the inorganic soils, but etch the concrete on a microscopic level, causing the soils to be flushed away from the surface of the grout.

Obviously, this is not a cleaning technique that should be used as a routine cleaning procedure, but dirty grout is a unique problem that many cleaning professionals face every day.

Knowing the basics of the stone and grout is the most important information a cleaning professional can use to make good decisions on cleaning procedures, techniques and detergents.

More information can be acquired by attending an Institute of Inspection, Cleaning and Restoration Certification (IICRC) Stone, Masonry and Ceramic Tile Cleaning Technician (SMT) class. The class schedule is available at

Dane Gregory is a cleaning veteran with more than 20 years of experience. An industry speaker and trainer, he currently co-chairs the Hard Surface/Commercial Division of the IICRC Certification Council and is chair of the SMT Technical Advisory Committee. He can be contacted at