Sitting in my office one morning I received a call from a very upset homebuilder. He told me he was building a two million-dollar home and had installed nearly 3500 square feet of a white statuary marble tile. Over the weekend one of the water pipes broke in a bathroom and completely flooded the home.

They managed to vacuum all the water and started to assess the damages. Beside warped wood, soaked drywall and an irate homeowner, the marble tile seemed fine except for some minor water spotting. After several weeks the replacement of warped wood and drywall was completed, but he noticed the white marble had turned yellow in many areas. At first he thought it might be some type of residue so they tried cleaning the marble with some bleach and water but the yellowing was still there.

Meanwhile, the homeowner was getting more and more irate and was threatening a lawsuit. It was at this point that he called me.

The problem of yellowed white marble is not uncommon. All over the United States I have encountered marble that has turned yellow, and even brown. Although flooding is a common cause there are several other reasons this color change will occur.

Improper Maintenance

As marble wears, the highly polished surface begins to become scratched and worn. The wearing of this polish causes the surface to become rough and become a magnet for dirt. If improper cleaners are used, this dirt begins to accumulate in the pores of the stone can will turn yellow. It is surprising how often I have seen this condition on marble. Upon investigation in these cases I have often found dirty mops being used. Mops used to clean the restrooms and/or kitchens were also used to clean the marble floors. Floors are mopped with strong cleaners or wax cleaner combinations or with no cleaners at all.

Cure: If you suspect yellowing due to improper maintenance the marble tile will have to be cleaned with an alkaline marble cleaner. I would suggest a heavy duty stone cleaner. Be sure the stone cleaner you buy needs to be alkaline and not an acid since acid cleaners will dull the polish. Apply the cleaner to the marble and scrub with a soft brush. Be sure to rinse the floor thoroughly. It may be necessary to repeat this procedure several times to remove all the imbedded dirt. If after cleaning the marble is dull I would suggest that you call us to professionally re-polish your floors then follow with an application of a good quality penetrating sealer (impregnator). If after several cleanings the yellowing is not removed then consider the next cause.

Wax Build-up or Coating

Many marble floors are coated with waxes, acrylics, urethane and other coatings. Most of these coatings are not specifically designed for use on marble floors. Some of these coatings are of poor quality and the coatings themselves will begin to yellow. It is not uncommon for coating to be applied in multiple coats. As the coating builds up it becomes soft and dirt is easily embedded in the soft layer. These coatings require frequent stripping which is often neglected.

Another possibility along these same lines is that process sometimes used for polishing marble floors is known as re-crystallazation. If this process is applied to a white marble floor that contains moisture it will turn the marble yellow.

Cure: To remove yellowing due to a wax or coating buildup the marble will need to stripped with a commercial wax stripper. I would strongly suggest having this done by a professional. These strippers often require the use of abrasive pads which can scratch and damage the marble surface. If you do try it yourself, before undertaking the entire project perform a small test to determine results.

If the marble tile has been recrystallized, it will be necessary to remove the recrystallized layer. This layer can often be removed by a professional polishing the tile with a powder marble polish containing oxalic acid. If this technique fails then the tile will have to be re-honed. It is strongly suggested that the polishing and honing procedure be performed by trained individuals. If these techniques fail to remove the yellowing then proceed to the next possible cause.

Iron Staining

Many white marble tiles contain naturally occurring deposits of iron. Iron is a mineral found in stone and can occur randomly throughout the stone. If iron is present in the marble tile, it will begin to oxidize when exposed to water or other oxidizers such as acids and household bleach.

It is for this reason that we recommend not using white marble in a shower.

White marble tiles can remain for years without yellowing then over time may slowly turn yellow, and in severe causes, may turn completely brown. This oxidation process is accelerated when the tile is saturated as in the flood in the above example. This process of oxidation is similar to the rusting of metal. If you expose a brand new nail to water and air it will turn brown and rust. The same process is occurring with the iron in the marble. If water and/ or air is eliminated the iron will not oxidize. This is the reason certain white marble suddenly turn yellow.

The process is difficult to reverse and replacement of the tile may be necessary. The following stain removal technique has proved successful in several cases. Before testing this procedure it is important to first determine if iron is the cause.

Testing for Iron:

1. Before assuming the marble is yellowed due to iron, be sure to attempt cleaning and stripping as outlined in the first two possible causes above. If these procedures fail then testing for iron will be necessary.
2. If a flood has occurred or excessive water was used first check the water for iron. If any amount of iron is detected then it is possible iron has entered the stone through the water supply. To eliminate the iron there are chelating chemicals that can be added to the water to prevent the iron from staining. This is very important if the tile is cleaned with this water.
3. Even if the water contains no iron the tile can be checked for iron content. We can remove one tile and have it analyzed total iron. If there are spare tiles that have never been installed it would be a good idea to also have them tested for total iron. If iron is present naturally in this stone, it will probably be detected in the spare tiles. If the results return with iron present then the following procedure should be tested.
4. We can check the tile for moisture using a moisture meter. If the tile contains water, it is very possible that iron is beginning to oxidize.

The Process for Removing Iron Staining:

1. Prepare a solution of water and the following chemical: Sodium Hydro sulfite and Sodium Metabisulfite. These chemicals are available in a product called Iron-Out® you may have seen at your plumbing supply or home center.
2. We will mix a solution in water and apply to the effected tile, and allow the solution to soak into tile and kept wet for several hours. It is important that the solution not be allowed to dry. After several hours pick up excess solution with a wet vacuum and rinse thoroughly with water and a chelating agent such as EDTA.
3. Be prepared to expect that the marble may need to be repolished since these chemicals can etch marble.

If the above procedure fails we can then prepare a poultice with diatomaceous earth and the Iron Out™. The poultice mixture will be applied to a small area and covered with plastic wrap. After 24 hours remove the poultice paste and rinse the area with water and a chelating agent. If the stain is removed, the entire floor can be treated. If the stain still remains then replacement is the only solution.

NOTE: There are also some new chemicals that are available which contain Ammonium Thioglycolate which look promising for removing iron oxidation.

The yellowing of white marble is a common problem. New installations should be sealed with a good quality penetrating sealer (impregnator) which will help prevent oxidation of the iron by eliminating moisture.

Are you a little confused about whether or not to seal your natural stone? You’ve done your homework and researched the topic on the web only to find that there are opposing opinions on the topic. Most experts recommend sealing all stone while others emphatically state that not all natural stone needs to be sealed.

SO WHAT IS THE ANSWER?

Let’s make it simple. To be safe, let me say that for the most part, all stone surfaces should be sealed for maximum protection. The worst case when you are dealing with a stone that is not very porous is that the stone will absorb very little sealer to achieve maximized protection. Don’t look the cost of the sealer as a waste of money though. Consider it added peace of mind.

(Tip: see the about testing absorbency first. If your stone is not very absorbent, buy only a very small bottle of sealer.)

Caveats

New Countertops? Some granite countertops are pre-sealed. Ask your fabricator or perform the Stone Absorbency Test (see sidebar).

Resined Stones: If the stone is resined¹, it may not need sealing. Perform the absorbency test to be sure.

Choosing the Correct Sealer

Many factors need to be considered when choosing the correct sealer.

1. Stone type:

   Many, if not most stones today are resined at the factory. Resining adds strength to more fragile stones thus creating a much larger supply of natural stones that can be used. You can learn more about resining by searching the Knowledge Base at www.stoneandtilepros.comAll stone is not created equal. How porous a stone is and how fast it will absorb a liquid is called the absorption coefficient. This coefficient is extremely important when choosing a sealer.Granite generally will have a higher absorption coefficient than a polished marble. Limestone can be extremely absorbent. The higher the absorption coefficient, the more difficult it will be to seal the stone adequately. (See sidebar for Stone Absorbency Test)

2. Stone Finish:

   The finish on a stone affects its absorption coefficient. A polished surface will be less absorbent than a honed or flamed finish. The above absorption test will determine how absorbent a stone is.

3. Stone location:

   Where is the stone located? Is the stone on the floor, wall, countertop? Is it in a kitchen, foyer, lobby, bathroom? What are they chances of it being subjected to spills or staining agents? Exposure to water, oil, heavy traffic, pets, etc. all need to be taken into consideration when choosing the proper product for protection. For example, a marble kitchen floor that is used daily will need a sealer that has both oil and water repellant properties. At the other end of that spectrum, dealing with a front foyer may only need a water repellant sealer.When protecting a busy hotel lobby floor, don’t be falsely assured that a wax coating will provide the optimal solution. It may track and scuff too easily, requiring costly upkeep. A quality impregnator and a polishing program may be needed to maintain the shine and protection.

4. Current Maintenance:

   How is the stone maintained? Is it exposed to harsh cleaning chemicals not intended for natural stone? On the other hand, if maintenance is neglected, a stone floor will have ground-in dirt and grit and if it has a high polish it will be worn. In this case, no matter how well it is protected, it will get dirty and dull. For example, a moderately busy hotel lobby floor that gets dust mopped and wet mopped every day may need a good quality impregnator. On the other hand, a stone foyer floor located in a home and not receiving any traffic does not need daily cleaning. An application of a water repellant impregnator may be all that’s necessary.The type of stone, its finish, its location, and how it is maintained all need to be considered when determining how to protect it. Evaluate each of these parameters carefully.How do we protect stone and other porous materials from staining? There are so many sealers on the market today. Which ones are best? Which ones really work?It can be very confusing trying to choose a sealer to protect stone. In the past several years the stone restoration and janitorial industries have bombarded the market with hundreds of products to seal, protect and polish stone.Fortunately, all of these products fall into only two major categories:

   1. Coatings
   2. Impregnators (Penetrating) Sealers

Coatings:

Coatings are sealers that place a sacrificial coating on top of the stone acting as a barrier to prevent water, oil and dirt from entering the pores of the stone.

Coatings can be classified into two general types:

1. Strippable
2. Permanent

Strippable Coatings

Strippable coatings are coatings that are designed to be easily stripped or removed from the surface of the stone. These coatings are made of polymers consisting of acrylics, styrene, polyethylene and others. They are usually water based. Many of the janitorial products are water based polymer type coatings. To identify these coatings look for terms on the label such as “metal cross link,” “high solids,” “high speed,” “acrylic,” “thermoplastic,” etc. When in doubt, ask. There are hundreds of different formulas of strippable floor coatings.

Most of them are designed for resilient tile floors and not for stone. If a coating is to be used, be sure it is specified for stone.

Permanent Coatings

Permanent coatings are coatings that are very difficult to remove. They are made of solvent based polymers such as polyurethane, epoxies, etc. These are not recommended for stone.

Impregnators (Penetrating) Sealers

Impregnators are designed to penetrate below the surface of the stone and deposit solid particles in the pores of the stone or to coat the individual minerals below the surface of the stone. Water, oil and dirt are restricted from entering the stone.

Impregnators can be solvent or water based and usually contain silicone, siloxane, silane, methyl silicate or other similar silicon derivatives. The latest impregnators now contain fluoropolymers².

Impregnators may also be classified as Oleophobic /Lyophoic (oil repelling) or Hydrophobic (water repelling).

Hydrophobic impregnators are designed to repel only water and water-based chemicals. Fruit drinks, coffee, tea, soda, etc. would be repelled by a hydrophobic impregnator.

¹ Infused with resins at the factory to increase strenght and density.

² Fluorocarbons are also lipophobic and oleophobic.

³ Lipophobicity, also sometimes called lipophobia (from the Greek λιποφοβία from λίπος lipos “fat” and φόβος phobos “fear”), is a chemical property of chemical compounds which means “fat rejection”, literally “fear of fat”. Lipophobic compounds are those not soluble in lipids or other non-polar solvents. From the other point of view, they do not absorb fats.

“Oleophobic” (from the Latin oleum “oil”, Greek ελαιοφοβικό eleophobico from έλαιο eleo “oil” and φόβος phobos “fear”) refers to the physical property of a molecule that is repelled from oil.

The most common lipophobic/oleophobic substance is water.

Oleophobic Impregnators

Oleophobic impregnators are designed to repel water and oil based liquids. Cooking oil, grease, body oils, etc. would be repelled by an oleophobic impregnator.

An oleophobic impregnator will always be hydrophobic, but a hydrophobic impregnator may not be oleophobic. Be sure to read product labels carefully to determine if they it is limited to being only hydrophobic. Some products are listed as oil resistant. Oil resistant and oil repellant are entirely different. Oil resistant will only slow down the absorption of oil into the stone. Oil repellant will prevent oil from entering the stone. Again, read product labels carefully. Be sure you are buying the right product for your particular situation.

NOTE —- Impregnators with Fluoropolymers are both oleophobic and hydrophobic.

IMPORTANT: Impregnators will do nothing to protect acid-sensitive stones from etching. They are designed to penetrate the stone’s surface to create a shield to protect staining agents from penetrating below the surface of the stone. Etching occurs on the surface of the stone.

COATING OR IMPREGNATOR?

How do you make the determination between a coating or an impregnator? They both have their advantages and their disadvantages. The following summary should be considered carefully when choosing the proper product:

Coatings – Advantages

Coatings are sealers that place a protective, sacrificial layer on the surface of the stone.

1. Coatings are generally economical. The initial application is relatively low.
2. Coatings are generally easy to apply. Unskilled labor can learn to apply them in a short time.
3. Coatings generally will provide a sacrificial coating on the stone. This layer will take most of the wear, preventing wear on the stone.
4. Certain coatings will provide added slip-resistance. (Although there are slip resistant treatments available just for natural stone surfaces.)
5. Coatings can be applied below grade. If a floor is located below ground level, a good coating may prove beneficial for protecting or waterproofing.
6. Coatings will generally provide various degrees of luster.

Coatings-Disadvantages

1. Since most coatings are typically softer than the stone itself, they will usually scratch, mar and scuff very easily, showing traffic patterns soon after application. This will require frequent buffing, burnishing or re-application.
2. Coatings can build up and can cause an unsightly appearance, producing an unnatural, wavy, plastic look to the stone.
3. Poor quality coatings can turn yellow. This is especially true if the stone is exposed to UV light.
4. Coatings require frequent stripping and reapplication. The chemicals and abrasives used in the stripping process may cause damage to the stone. Typically, certain stripping pads and stripping brushes can scratch some softer stones.
5. Some wax strippers can harm certain stones such as agglomerates, eating away at the polyester binders.
6. Certain coatings may block the breathing capability of the stone. Moisture can become trapped below the surface and may lead to spalling.

Impregnators-Advantages

1. Most impregnators will not change the appearance of the stone.
2. Most impregnators do not require frequent applications. Since the impregnator is below the surface, it will generally last several years before reapplication is necessary.
3. Most impregnators are not affected by UV light since they are below the surface where UV light cannot penetrate. For this reason they can be used outdoors.
4. Impregnators are typically hydrophobic, while some are oleophobic.

Impregnators – Disadvantages

1. Impregnators that are solvent-based produce noxious and flammable vapors during application.
2. Solvent-based impregnators are harmful to the environment producing high VOCs (volatile organic compounds). For this reason, some are restricted in certain states. Always check the Safety Data Sheet (MSDS/SDS).
3. Impregnators require a semi-skilled person for application. Proper training is highly recommended.
4. The initial cost of most impregnators is relatively high.
5. Impregnators in general cannot be used below grade to resist hydrostatic pressure. Since the stone is still capable of breathing, water can be forced through the stone by pressure.When choosing the proper product for protection, the above guidelines should help. Always talk with the manufacture or distributer, and let them know where you plan to use their product. They can be very helpful if you tell them all the conditions that apply.

Sealing: Do it Yourself or call in a PRO?

SEALING: DIY or Call in a Pro?

Is sealing a job for the homeowner, or should you hire a qualified professional to do it for you? Consider the following pros and cons.

The obvious pro for doing it yourself is you save on labor costs. However, if it is not done correctly it could result in problems.

For example, the surface must be thoroughly and completely cleaned. If not, you take the chance of sealing in dirt and debris. Also, keep in mind that the sealer is intended to fill the pores and coat the exposed minerals in the stone, not to coat the surface. If residual sealer is not completely removed from the surface of stone, it may cause problems, including a haze on the stone’s surface that may develop as the sealer dries. Once it has dried completely, sealer can be very difficult to remove, often requiring professional assistance.

Different sealers perform differently in different environments and on different stones. Hiring a pro to do the job may end up saving you in the end. A pro will know which is the best sealer for the job and will use equipment and techniques that allow them to get the job done efficiently.

More often than not, what customers are looking for is that beautiful shine their marble floors had when they were new.

Marble is a relatively soft stone. When it becomes dull and scratched, it loses its shine and luster. Many people see this and think their stone is dirty and needs professional cleaning. In actuality, the stone needs to be refinished and polished to restore the shine it had originally.

Why Marble Shines

In diagram A above, we see an illustration representing a rough or scratched piece of stone. When light is reflected from the stone the light rays become scattered producing a dull, flat appearance to our eyes.

In diagram B, a very smooth stone, the light is reflected on the surface and the light rays return in a parallel pattern producing a deep reflective appearance. This same optical property can be observed on a pond. When the wind is blowing and the surface of the pond is wavy, it becomes difficult to see a reflection; when the air is still and the pond is calm, a deep reflection can be observed. So in order to achieve a deep shine on stone all that really needs to be done is to smooth it until it shines.

How Shine is Restored

The deep shine we see on polished stone is achieved by rubbing the stone with a series of abrasive materials. The process is very similar to sanding a piece of wood. The stone is rubbed with a coarse abrasive grit, followed by finer and finer grits until the stone becomes smooth. The scratches left behind from one grit are removed by the next, creating finer and finer scratches. The process continues until the scratches are microscopic. The shine on the stone is achieved by abrading the surface to the point at which it becomes extremely smooth and starts to develop some reflectivity. The shine on the stone is thus a product of optics.

Stone Restoration and Refinishing

This process is commonly referred to as stone restoration or stone refinishing and is something that should only be done by a qualified professional stone restoration company.

THE BEAUTY OF IT ALL

Of course your first consideration is how it will look. With today’s options there is no reason to settle for anything less than stunning. Start with what is the overall feel you are aiming for. What type of decor will you be using in the room? A Southwestern style may require a Mexican tile floor. If the room is very elegant, marble or granite may work best. Be sure when selecting your tile that you take into consideration the decor of the room and that the tile compliments the mood.

Choose design, colors and styles that you will not tire of easily. Tile will often last as long as the house, so be sure you are happy with your selection. If in doubt, consult with an interior designer. Many tile and stone stores have designers on staff that will be more than happy to assist you with the proper selection. For inspiration and ideas, refer to tile and stone inspiration galleries such as the one on stoneandtilepros.com.

TRAFFIC AND WEAR

One of the biggest mistakes made in tile selection is choosing a stone or tile that is not suited for the traffic or usage it will be subjected to. Some marbles are very soft and should not be used in any area that will have to endure high traffic. A softer marble in a busy hotel lobby is a poor choice but may work well in a residential foyer. How easily does the material scratch?

TIP An easy test to perform is to take a pocket knife blade and run it lightly across the tile. If the blade leaves a scratch it will probably wear poorly in high traffic areas.

For the Architect or Designer refer to ASTM C241- Abrasive Resistance

STAIN AND ACID RESISTANCE

I will never forget a customer of mine who was a gourmet cook and installed beautiful white marble on her kitchen countertops. The marble was highly polished, very soft and not sealed. Needless to say in less than a month the marble was stained with every color of the rainbow and had lost its deep shine. Look carefully at the use the tile is to receive and determine how easy it will stain or etch. If you must use marble on a well-used kitchen countertop, be sure to seal it properly to inhibit staining agents from being able to seep in. The more absorbent the tile or stone, the more likely it will stain if not sealed. Etching, on the other hand is caused from acidic liquids coming in contact with acid-sensitive stones. Marble is rarely recommended for a kitchen because of its acid sensitivity.

For the Architect and Designer refer to ASTM C97-Absorption and Specific Gravity.

COST

Unfortunately cost is usually the deciding factor when selecting tile or stone. Cost can also be very misleading.

An inexpensive stone or tile may fit into your budget, but if it wears easily the cost of restoration, repair or replacement often will ultimately be more costly than not. Thoroughly investigate the maintenance requirements of the selected tile. Shop around and ask a lot of questions. The tile and stone market is very competitive so bargains can be found.

Warning: Tile and stone are available in different grades. The poorer grades may be cheaper but will have imperfections and flaws. Examine each tile carefully before it is installed.

TIP It is also a good idea to spend a little extra and buy spare tile in case tiles need to be replaced later. This is especially important with marble and ceramic since colors and patterns can be impossible to match later on.

Whatever your budget, do your homework and buy the best quality you can afford.

SAFETY

It is astonishing how many injuries occur each year due to slipping and falling. When choosing tile or stone, be sure it is not slippery. A highly polished granite tile on a shower floor may be a poor choice and a slip hazard, for example.

Honed, textured or flamed finishes may be less slippery. Ask us about treatments that can be applied to the surface of tile and stone to make it slip resistant.

For the Architect or Designer refer to ASTM test methods for coefficient of friction.

INSTALLATION

Who will do the installation? Many simple tiling projects can be performed by the do-it-yourselfer but more intricate projects and certain tiles, such as marble, should be left to the professional installer. Be sure to choose an installer familiar with installation of the tile type you select. Installation of ceramic tile differs from installation of stone.

SUB-FLOORING

What is the condition of the sub-floor (the floor the tile is to be installed on)? Is there an existing floor material or tile? Many times the sub-floor will have to be properly prepared before installation can begin. If you are tiling over an existing vinyl or tile floor, different setting materials will be needed so that proper bonding of the new tile will occur. If in doubt ask us for advice.

MAINTENANCE

Maintenance is the most overlooked factor when choosing stone or tile. Just because a stone or tile cost more doesn’t mean its maintenance requirements are less. There is no such thing as maintenance free! A twenty-cents-per-square-foot vinyl requires maintenance just as much as a thirty dollar per square foot stone. Be sure to understand the maintenance requirement of the tile or stone you select before you buy. Ask to see the maintenance guide for the tile type. It may also be a good idea to check with a friend or neighbor that has the same type of tile and ask them how easy or difficult it is to maintain.