Friday, March 5, 2010

Moisture- Stone Enemy Number One


Most of the problems associated with stone tile installation can be traced to moisture or water intrusion of some kind. Many stains are caused by the presents of water. Water is an essential ingredient for the setting cleaning and restoration of stone but it can also be its number one enemy.

What problems are associated with moisture and water. The following is a brief description of the problems, there prevention and remedies:


Efflorescence appears as a white powdery residue on the surface of the stone. It is a common condition on new stone installations or when the stone is exposed to a large quantity of water, such as flooding. This powder is a mineral salt from the setting bed. To remove efflorescence do not use water, buff the stone with a clean polishing pad or #0000 steel wool pad. The stone will continue to effloresce until it is completely dry. This drying process can take several days to as long as one year.


Subflorescene is what happens when the mineral salts migrate and do not make it all the way to the surface. In the efflorescence condition above, the slats are deposited on the surface of the stone. In subflorescene the salts crystallize just below the surface, causing stress within the pores of the stone. The result is a condition known as spalling which appears as pits in the surface of the stone. subflorescence is very common on green marbles and is very common on almost all stone surfaces where de-icing salts are used.

Iron Staining

Many light colored stone contain naturally occurring deposits of iron. Iron is a mineral found in stone and can occur randomly throughout the stone. If iron is present, it will begin to oxidize when exposed to water or other oxidizers such as acids and household bleach. Stone 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 stone is saturated with water. 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 stone. 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 stone 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 with a good alkaline based stripper. 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. There are several inexpensive test kits available that can be used to check the iron content in water. Check with your local plumbing supply store or store carrying water softening supplies. 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 stone is cleaned with this water.

3. If the water contains no iron and even if it does the stone should be checked for iron content. Remove a small sample of the stone and contact a testing lab and have them analyzed it for total iron. If there are spare tiles that have never been installed also have them tested for total iron. If iron is present naturally in this stone, it will probably be detected in the spare tile. If the results return with iron present then the following procedure should be tested.

4. Check the stone for moisture. A moisture meter is a useful instrument that can be employed to check the stone for moisture. If the stone contains water, it is very possible that iron is beginning to oxidize.

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(TM) from your plumbing supply or home center. Mix a solution in water and apply to the effected area. Allow solution to soak in and keep wet for several hours. Do not allow solution to dry. After several hours pick up excess solution with a wet vacuum and rinse throughly with water and a chelating agent such as EDTA. Be prepared to repolish any marble since these chemicals can cause etching.

2. If the above procedure fails than prepare a poultice with diatomaceous earth and the Iron Out(TM). Mix the poultice into a thick paste and apply to a small area. Cover the poultice with plastic and allow it to sit covered for 24 hours. After 24 hours remove the poultice paste and rinse the area with water and a chelating agent. If the stain is removed, the entire surface can be treated. If the stain still remains then replacement is the only solution.

Before the above procedure can be performed, it is important that the effected area be dry. If water or moisture are still present, oxidation of iron may continue

The yellowing of stone 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.

The above procedure has proven successful in some cases of iron staining however if the following test does not produce the desired results I would recommend replacement of the effected areas.

Marble and limestone in constant wet areas such as showers and pools, etc may be impossible to remove iron. The stone as well as adjacent materials such as grout etc will also be effected.


several type of thin stone tiles are very susceptible to warping. Many of the green marbles and a few agglomerate marbles are notorious for this warping condition. Many of an installer have had the surprise to find that there tile installation has become warped overnight. Why does this a happen and can it be prevented. Warping is caused by water. Green marble set with any water based material will have a tendency to warp. The mechanism of why the tile warps is somewhat a mystery. Some believe that the water fills the pores of the stone and when the water evaporates the orientation of the stones crystal change and cause it to warp. Whatever the reason, one thing is for sure, green marble can warp when set with water based materials.

Cure: Once a green marble tile warps it is difficult to repair. Attempts have been made to grind the tile flat , but this usually fails since additional water is introduced during the grinding process. The green simply warps again.

Prevention; The only way to prevent warping is to install it properly with a non-water based material such as epoxy. Some installers have also ben successful in sealing the back of the tile with epoxy and installing it in a water based system(see July Stone & tile Report). Do not attempt to seal the back of the tile with a silicone sealer. The silicone acts as a water repellant and will cause the setting material to fail resulting in a bond loss.


Erosion is a condition found when stone is exposed to constant amounts of water. This is especially true with marble that is used in water fountains. While marble is a very decorative material, it is one of the worst materials to use in or around water. Marble is composed of calcium carbonate. Calcium carbonate is a water soluble mineral. Quite simply this means it will dissolve in water. Want proof, visit the Grand Canyon. Erosion can be recognized by a slow deterioration of the stone surface. With polished stone the polish will be worn off. In older installations, the stone may become very soft, brittle and in extreme conditions, it will powder.
If any architects or designers are reading this article I beg you no to use marble for water fountains. If you do, plan on very high maintenance costs and plan on replacement in about five to ten years if not sooner.

Stabilizing erosion:

If your faced with trying to stabilize a marble fountain that is already deteriorated there are some treatment that can be applied that will extend the life of the marble. These treatments are general called consolidants and serve to replace the natural binders that are lost through erosion. Consolidants can be tricky and quite often will cause discoloration of the surface. Be sure to test the consolidant carefully before use.

Mineral crusts or Lime Putty

Mineral crusts or lime putty can be recognized by its white crust like formation on stone surfaces. These crusts are often found on outdoor stone stair, water fountains and other areas where stone is exposed to water. The crusts are a deposit of hard mineral salts consisting of calcium, magnesium. These minerals ordinate form the soil, setting bed or from the water itself. These salts are similar to efflorescence in that they are a mineral. They differ in that they form a hard crust that can be difficult to remove.

Crust Removal

there are only two ways to remove these mineral crusts. Abrasion or chemical. The mineral salts should be remove with an abrasive. I have found that a stiff non-ferrous wire brush can work well. Brushes can also be purchased that attach to an electric drill. Be careful and do not get to aggressive. Avoid damaging the stone surface.
Quite often abrasion alone will not remove all salt deposited. Strong Acidic chemicals will be required. These chemicals can be purchased from most chemical companies that supply stone cleaning products. Be careful when using these products around calcium based stone since the acid can also damage the stone itself.


The best prevention from mineral salts is to prevent moisture form entering the stone. On steps and fountains make sure all grout joints are caulked with a water proof material. When installing steps outdoors make sure a water proofing barrier is used. It is also a good idea to use a good stone impregnator on all surfaces to prevent water from entering the stone. Caution; Stone inpregnators will not waterproof stone. Do Not use them where hydrostatic pressure is a concern.


To properly test for moisture a protimeter is necessary. A protimeter is an instrument that reads moisture. The common protimeter has been designed for use with wood, drywall and other similar substances. The protimeter contains two sharp probes that are inserted into the wood or drywall to give a direct moisture reading in percent. Unfortunilty you can not push these probes into the stone, but the protimeter can give you important data oon stone moisture. By placing the pins so that the just touch the stone a relative reading can be obtained. For example, A reading of 0-6% is considerely relativly dry. A reading between 7-20% is wet. A reading of of 20% is very wet. These readings only tell you that the stone is wet, a little wet or dry. A direct percent reading can not be obtain with these instruments, but can provide useful information.

Another simple technique for determining moisture in stone is to take a piece of plastic about 12 inches square and place it on the suspected stone. Tape all four edges and allow it to stay overnight or 12 hours. After 12 hours, if there is any moisture present , you will see condensation collecting under the plastic.


A protimeter can also be used to check for the presents of soluble salts. The following procedure will only tell you that salts are present. It will not tell you how much or what type. But in many cases the simple presents of salts can indicate potential spalling and/or pitting.

For this test you will need the following materials:

A rubber block
filter paper
distilled water
a protimeter

Any type of rubber will do as long as it is clean and does not contain any salts. A piece of hard plastic can also be used. Filter paper can be purchased from a scientific supply store and sometimes from the supplier who sells protimeters. Distilled water can be purchased from the grocery store.
The forceps are used to pick up the filter paper.

To check for soluble salts pick up a filter paper with the forceps. DO NOT touch the filter paper with your fingers. The human skin contains soluble salts which could be transferred to the paper giving a false reading. Place the filter paper on the rubber block. Add a drop of two of distilled water to the filter paper. Place the probes of the protimeter to the filter paper and record the reading. Next, take a new filter paper and place it on the stone to be tested. Add several drops of distilled water and take a reading. Record the reading on a piece of paper.

If the reading obtained on the filter paper from the stone is higher, then there are slats present. If it is the same or lower, salts are absent. The protimeter works by reading ionic changes. When salts are dissolved in water, the ionic changes are higher, which gives a higher reading.

Sustainable Terrazzo Floor Care-Dispelling the Myths

Sustainable Terrazzo Floor Care-Dispelling the Myths

As the world moves towards more sustainable design and maintenance myths are starting to be propagated which only leads to confusion. School superintendents, custodians and teachers are being bombarded by false information. The following are some of these myths and the truth behind them as it applies to floor care

Myth #1- Coatings, waxes etc are used as a sacrificial layer to protect the floor.
FALSE- Coatings such as acrylics, epoxies, urethanes commonly found in floor finishes are soft compared to the natural hardness of terrazzo which is basically concrete and marble. Due to their inherit softness they tend to trap and hold dirt and debris which contributes to accelerated wear of the surface.
A simple test can be performed to prove this. Take a tile and coat one half of it with a standard floor finish and leave the other half polished using a sustainable method. Allow the tile to sit in a room for a week. After a week you will notice that the coated side has more dust than the uncoated side. Next take a rag and wipe it across both sides of the tile. You will note that the drag on the rag is much greater on the coated side vs. the uncoated side. Now imagine how hard it is to remove this dirt and debris with a dust mop on coated floor.

Myth #2- Terrazzo contains asbestos and should not be ground
Let’s take a look at what terrazzo consists of. It is composed of concrete and marble chips or epoxy and marble chips. None of these components contain asbestos. Some concrete mixes do contain fiberglass particles which under a microscope can easily be mistaken for asbestos. In addition we have taken core samples of terrazzo on several occasions and have had them tested for asbestos. In every case no asbestos was found.

Myth #3 -Using Green and sustainable methods cost more
False; In fact sustainable maintenance will reduce cost dramatically. Not only will less time be required to dust mop and wet mop, but you have totally eliminated all chemical costs. Several studies can be found at www.boylanstonerestoration that will show that on average the cost savings is around $1.85 per square foot per year. In addition the payback on the initial restoration cost can be less than 3 years.
Myth #4 –Going green will cost jobs
False: most floor care programs spend nearly 70 % of manpower on floor care. Due to budget cuts, other areas of maintenance are being neglected. In fact based on our informal surveys more and more work is being placed on maintenance staff. By reducing the maintenance costs and labor required on floor care, manpower can be directed to other neglected areas.

Myth #5- A natural polished terrazzo floor will stain without a protective coating.
False: The natural polishing process closes the pores of the terrazzo which reduces the absorption of liquids. In many of our terrazzo restoration projects coffee was spilled and dried on the floor. The dried coffee was scraped up leaving no visible stain.
Myth #6- Stripper, coating and cleaners are now available in Green Formulations
Caution must be excerised when looking at what constitutes a “green” product. Many chemical companies have reduced the percentage of hazdourous chemicals in their formulations. However this does not make the product any safer. Many articles have discussed this and have called it Green Washing. A great example of this is in a article by The Environmental Working Group( , which uses the cleaner Simple Green as an example. There article states that Simple Green claims to be non-toxic and biodegradable but failes to mention that the principal cleaning ingredient it contains is a possible human carcinogen.The hazardous ingredient is still present along with all the dangerous it exhibits. To be totally sustainable it is best to use NO CHEMICALS at all.

The myths that are circulating must be investigated and common logic applied to them. Many of these myths are put forth by chemical companies who are trying to market there hazdourds , health threating products. A simple review of the MSDS will show many of the ill effects of these chemicals.

A New But Old Polishing Proceudre for Natural Stone Flooring

A New But Old Polishing Procedure for Natural Stone Flooring
By Frederick M. Hueston PhD
Putting New and Old in the same sentence is somewhat of an oxymoron. But in this case both of these adjective apply. What I am talking about is a polishing system for stone flooring that was used many years before chemicals came into existence and is now fast becoming the preferred method specified by architects and others. The word “Green” has entered our industry and I am finding that many projects across the US are now specifying that a green and sustainable restoration process be implemented in restoring both natural stone and terrazzo surfaces. This article will present not only what is sustainable but will give you an alternative to traditional polishing methods that is fast becoming the preferred method.

What is Green?
Everywhere you look individuals, government agencies, universities and schools and even private businesses are going green. As we hear news about global warming and how we are polluting our own environment, it is of utmost importance that we all do our part in saving our planet not only for our present generation but for generations to following.
What Does Going Green Mean?
The term Green or Going Green has entered our vocabulary but few really know what the term means. Going Green is principles that minimize the use of nonrenewable resources and seek to prevent air, water and ground contamination and other activities that degrade the environment. According to The US Green Building Council worldwide buildings account for 17% of fresh water withdrawal, 25% Wood Harvest, 33% CO2 emissions and 40% material and energy use.
Going Green is simply changing the way we build, operate and maintain buildings to reduce the negative impact it is having on our environment.
Many small businesses feel that they are too small to make an impact on the environment. Even individuals feel the same. Take a look at the following facts and you will see this is simply not true.
• A single quart of motor oil, if disposed of improperly, can contaminate up to two million gallons of fresh water.
• A 1/32" leak in a faucet can waste up to 6,000 gallons of water a month, or 72,000 gallons a year.
• Americans throw away 25 billion Styrofoam coffee cups every year, and 2.5 million plastic beverage bottles every hour.
• The amount of wood and paper we throw away each year is enough to heat 50 million homes for 20 years.

And the list goes on and on.

Stone Restoration and Green
Traditionally the restoration, repair and maintenance of stone and terrazzo surfaces use chemicals that are harmful to the environment and to people in general. Chemicals such as polishing compounds contain harmful acids. Solvent based cleaners and sealers emit harmful VOC’s. Not to mention the carcinogens and toxic effects many of these chemicals have on humans. The procedures used to restore stone surfaces also produce a copious amount of waste and use large amounts of fresh water.
I am currently working with a stone restoration company that is taking steps to eliminate all these harmful chemicals and processes. This company has developed methods to restore , repair and maintain stone surfaces using no harmful chemicals. As matter of fact the restoration and polishing of marble, granite, limestone and terrazzo uses no chemicals at all. Here is a summary of their process
The floor is ground and resurfaced using a fixed diamond abrasive and water. These abrasives are similar to sandpaper but differ in that there is no grit removed or left behind on the floor. The diamond abrasive is fixed to a pad. There are no chemicals used at all.
The water used will be recycled and reused in a specially designed system.
To polish the stone or terrazzo super fine abrasives are used. These abrasives contain no harmful chemicals.
Many stone restoration and janitorial companies are also using floor finishes to achieve a high luster on the stone or terrazzo surface. In addition to these finishes containing chemicals that are harmful to the environment. They also have a negative impact on the esthetics of the surface in the following ways:
-Most finishes used on stone and terrazzo are soft and tend to show wear and scuff marks in a very short time. This increase the amount of maintenance as well as cost for daily maintenance
-All floor finishes at some point will need to be stripped off. The chemical strippers used are caustic and can cause damage to the stone or terrazzo, not to mention the environmental impact.
-The old finish once it is removed will need to be disposed of. Most of these waste finishes are considered a hazardous waste.
-Most finishes do the opposite of what they are designed to accomplish. That is they become a dirt magnet. I have conducted experiments that show a coated surface will attract more dirt than a surface restored using a green system.
Even today’s stone restoration companies are using polishing compounds that contain dangerous oxalic acid.
A Green stone and terrazzo restoration process have no negative impact on the building environment or the occupants since no chemicals or finishes are used. The maintenance requirement after the stone or terrazzo is restored is reduced by as much as 50% or more saving on labor and chemicals.

Can Natural Stone be polished without the use of chemicals?
Many stone restoration companies will argue that it is impossible to achieve a deep high reflection on natural stone without the use of chemical polishes. This in fact is not true. Mechanical polishing using diamond abrasives alone with the proper equipment can achieve results that are as good as or superior to chemical polishes. These methods will be discussed and presented my next article.

Be Wary of Green Washing
Caution must be excerised when looking at what constitutes a “green” product. Many chemical companies have reduced the percentage of hazdourous chemicals in their formulations. However this does not make the product any safer. Many articles have discussed this and have called it Green Washing. A great example of this is in a article by The Environmental Working Group( , which uses the cleaner Simple Green as an example. There article states that Simple Green claims to be non-toxic and biodegradable but failes to mention that the principal cleaning ingredient it contains is a possible human carcinogen. The hazardous ingredient is still present along with all the dangerous it exhibits. To be totally sustainable it is best to use NO CHEMICALS at all.

Tuesday, April 1, 2008


By Frederick M. Hueston

The following is a reprint of an article I wrote back in 1990. I have edited some of the text to bring it up to date. My opinion on this process is still the same as it was in 1990. With that said there are some uses for this process, however care must be exercised in its use. Most of the damage I have seen since 1990 by this process results from the overuse of the product as well as the lack of trained personnel who apply it. The following reprint should give you some useful information on this process and the care that must be used when using it.

To answer the problems experienced by customers who had dull and scratched marble. I tried to find the best and most practical solution to the restoration of their marble floors, walls, etc.
Since this is a relatively small industry, there weren’t too many good sources. I did find some self-proclaimed “experts” who introduced me to the idea of “re-crystallization” as a safe and easy method of restoring and polishing marble and stone. They touted it as a time proven process which had its roots in the marble industry in Europe. It was alleged to be safe, easy to apply and was both slip resistant and permanent. In short, it was the perfect solution for most marble restoration and maintenance problems.
Having been raised in the “old” school, I instinctively doubt anything that appears “too good to be true”. Experience has taught me that most of those “too good to be true statements” usually turn out to be exactly that!
My business reputation is at stake whenever I recommend or use a product or procedure. I don’t take that responsibility lightly. So, I endeavored to get answers to some specific questions about this “re-crystallization” process (from the systems’ promoters).

Question #1. Does the “re-crystallization” process contain waxes?
Crystallization Answer: No.

Question #2. Does the process allow the stone to breath (transpire)?
Crystallization Answer: Vague generalizations and evasive replicas.

Question #3. How does “re-crystallization” react with stone?
Crystallization Answer: Evasive generalizations.

These evasive non-answers surprised me. Perhaps there was something that these crystallization “experts” did not know---or did not want me to know.
Though I am in stone consultation business, my formal education is in Chemistry. I had a natural curiosity about this wondrous process called “re-crystallization”. After all, if it worked, it would be great for my business. I determined to do some research on my own. Following is a summary of my research.


The term “crystallization” is defined as the process by which a substance takes the form of a crystal structure. Most minerals are crystal shaped. The term “re-crystallization” implies that a substance has been crystallization a second time. In other words, changed from one crystal shape to another.
In geology, re-crystallization takes place---under great pressure at high temperatures--- deep in the earth and over thousands of years. My research showed that the natural re-crystallization of minerals such as those found in stone is unlikely to be obtained with the so-called packaged chemical “re-crystallization method” being marketed by a number of companies. We can therefore assume that the term “re-crystallization” is used only as a marketing term.
For the purpose of this article, we will use this term---re-crystallization---only as a description of the chemical process that follows.


I obtained Material Safety Data Sheets (required by OSHA for all chemical products) from a good sample of “re-crystallization” product distributors.
From them, I learned that all the “re-crystallization products contained a fluorosilicate compound. All contained an acid of one type or another and almost all contained varying percentages of waxes and acrylics.
To understand how these ingredients react with marble, one needs to understand the makeup(natural composition) of marble, itself. The main constituent of marble is a compound called Calcium Carbonate (CaCO3). Calcium Carbonate, along with other accessory minerals, makes up what we know as marble.
When an acid is dropped on marble it will burn and etch the surface leaving a pitted, dull spot. The reaction (Formula 1) illustrates what happens when an acid and marble come in contact with one another. The bond between the calcium and the carbonate is broken, producing water and carbon dioxide gas and the calcium carbonate is destroyed. In other words, acid destroys marble. All re-crystallization fluids contain acids.
If you have any doubts, place a drop of re-crystallization fluid on a piece of marble, wait just 30 seconds and wipe it off. You will find that it has etched.


CaCo3 + HCL ---------------à Ca+ Co3 + H2O

The main ingredient used in re-crystallization fluid is a group of compounds called flurosilicons. Three types of fluorosilicates can be found in re-crystallization fluids: (1) Aluminum fluorosilicate (2) Magnesium fluorosilicate and (3) Zinc Fluorosilicate.
First used in 1883, flurosilicate compounds were used in an attempt to preserve marble statues that were crumbling. The effects of these compounds on stone were studied by several researchers and were found to have detrimental effects on the stone.
It was found that flourosilicates deposit an enamel on the surface of the stone which completely blocks its pores. The stone suffocates, begins to break apart and rot. The results of these studies can be found in the book Stone Decay and Conservation written by Glovanni G Amoroso and Vasco Passins---ELSEVIER, Amsterdam, Lausanne, Oxford, New York 1983.
The re-crystallization process uses an acid that attacks the calcium carbonate in the stone (Reaction 1). This reaction destroys the calcium carbonate and releases the calcium ion. The fluorosilicate compound then attaches itself to the calcium ion forming a new compound (Reaction 2 & 3). This new compound, calcium fluorosilicate forms an imperious film on the surface of the stone---totally blocking its pores.




Based on the preceding facts. I have reached the following conclusions:

FACT: Marble and stone must breathe (transpire). If the pores are blocked, moisture from the slab (condensation, etc.) will be trapped and the stone will begin to break down.

FACT: The re-crystallization process places an impermeable coating of fluorosilicates on the stone, completely blocking its pores.

FACT: Acid will destroy marble and stone.

FACT: All crystallization fluids contain acids.

The above facts are clear and incontrovertible evidence. What is even more startling are the dozens of marble floors and walls I have seen that have been destroyed by this process.
Along with other responsible stone restoration firms in the industry. I urge anyone---even thinking about allowing a “crystallization” process to be used---to test the proposed products on a marble sample and judge the results for yourself. You will find the rapid deterioration of the marble frightening.
For the names of responsible stone restoration firms, you are invited to write Building Stone Institute, Marble Care and Maintenance Companies, 420 Lexington Ave. New York, New York 10170.


The extensive marketing of restoration methods using “re-crystallization “ is a very serious matter for everyone in the industry. The alarming increase in the number of complaints regarding permanently damaged marble and other stone floors and walls is hardly conducive to increased sales and use of our fine products. This damage could have--- and should have---been avoided, I urge you to advise all your customers of the potential damage from any of these “re-crystallization” methods being marketed. Now that we know exactly what this so-called “re-crystallization” process is, we can answer the frequently asked question---Can a floor or wall that has been “re-crystallized” be saved?

Here are some guidelines:

First, determine that crystallization has actually been used. For a start, ask the customer. Some will tell you, others will flatly deny it, and still others simply won’t know.
If the shine on the marble or stone looks wavy (acrylic looking) then you can be fairly sure there is some type of coating on it. It is relatively easy to determine the type of coating. To do this two chemicals are needed: (1) a commercial wax stripper and (2) methyl chloride (wood furniture stripper).
Place a small amount of each chemical on the stone. If the commercial wax stripper removes the film then you are dealing with an acrylic type finish. Simply remove the finish with the stripper before starting the normal restoration or polishing process.
If the commercial stripper does not remove the coating but the methyl chloride does, then you have a urethane based coating. Remove it with methyl chloride or grind it off.
If neither one of these strippers removes the coating, the chances are it has been re-crystallized.
Another reliable clue is the presence of swirls on the marble (or other stone). These are caused by the use of steel wool during the re-crystallization machining process.
Make sure that before you attempt any polishing or grinding that you have determined the type of coating on the marble (stone). Be aware that there may be more than one coating---possibly an acrylic coating placed on top of a re-crystallization” coating, test several areas, to be sure.
If it is discovered that the marble (stone) has been re-crystallized---can it be saved?
This will depend on the severity of damage. For example. Travertine and Crema Marfil will exhibit damage almost immediately. Other stones, such as granite, will take longer. Still others will not show any apparent damage until the re-crystallized layer begins to wear off. It pays to become familiar with the various types of marbles and other stones.
There are a few general rules to determine the extent of damage.
These higher the CaCO3, the more destructive the re-crystallization will have been.
The greater the number of applications of re-crystallization---over a period of time---the greater the chance of irreversible damage.
The veining in some marble will be adversely affected first. If these veined areas crumble easily, when probed with a blunt instrument, the stone may be damaged beyond repair. If the amount of veining is not too extensive, it may be saved by filling with a poly resin such as Akemi.
Perform several Patch Tests. Grind the stone and bring it up to a polish. If the stone polishes, the chance are it can be saved. CAUTION: make absolutely sure you have removed the re-crystallized layer entirely. We recommend starting with a 60 grit for most stones.
A FINAL WARNING: some of the companies have begun to eliminate the term “re-crystallization” and are substituting “marble polishing” or “Vitrification”. Be cautious. Even if it carries the name of a nationally known chemical firm, check their claims. Ask to see the Material Safety Data Sheets. If the process contains fluorosilicates, do not use it. The hard sell “marketing” (selling franchises) of these products is bringing us very close to an epidemic of severely damaged marble (stone) floors. A few clients (who simply did not know better), having just installed brand new marble floors, have had terrible damage done to them. We all know that there is no such thing as a totally “maintenance free” floor. Marble, granite, slate---whatever---must be maintained. The type of maintenance varies with use. Obviously, an entrance foyer of a residence requires a very different maintenance schedule than the lobby of a downtown high-rise office building or a major hotel.
Maintenance can be done quite simply, using recommended products and procedures. However, after extensive wear and tear---over a long period of time--- a client may wish to have professional restoration work done. This can best be achieved by employing a responsible firm using traditional methods. These firms will look at an installation and provide a written estimate not only of the costs involved (usually figured on a square foot basis) gut also the materials to be used. They should have their own equipment---and trained crews--- who have quality experience with the marble and other stone floors.

Update: Since 1990 I have conducted several vapor emission test on marble and stone surfaces to determine if this process in fact does not allow stone to breathe. In my testing I have found that in most cases this process does in fact block vapor emission.

Sunday, February 17, 2008

Designing a Sustainable(Green) Stone Floor Maintenance Program

Designing a Sustainable (Green) Stone Floor Maintenance Program
By Frederick M. Hueston PhD

Walk into any stone, terrazzo or janitorial chemical supplier and you will find an endless selection of cleaners, sealers, restorers, etc to keep you terrazzo and stone floors looking new. The problem is many of these chemicals can be harmful to the user, occupants and the environment. How does one design a program that is not only sustainable and safe but to also keep your terrazzo and stone flooring in like new condition?

Fortunately there is an effective way to not only maintain these surfaces but also to keep them looking new. The following guideline will show you how to develop a sustainable maintenance program. This is especially important for schools, hospitals and other buildings were children and people sensitive to these harmful chemicals are present everyday.

The dangers of floor strippers, finishes etc have been studied by many organizations including universities, etc. Here is a partial list of those studies

- Green Seal Report
Floor Care Products: Finishes and Strippers

-Safe and Effective Use of Floor Finish Strippers
Janitorial Products. Pollution Prevention Project
Sponsored by US EPA

-Health Hazard Evaluation Report 95-0313-2589, University of Michigan Hospitals, Ann Arbor, Michigan

-NIOSH [1990]. NIOSH criteria for a
recommended standard: occupational exposure to
ethylene glycol monobutyl ether and ethylene
glycol monobutyl ether acetate. Cincinnati, OH:
U.S. Department of Health and Human Services,
Public Health Service, Centers for Disease
Control, National Institute for Occupational
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-Ruth JH [1986]. Odor thresholds and irritation
levels of several chemical substances: a review.
Am Ind Hyg Assoc J 47:A142–A151.
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and health effects. World Health Organization
Regional Office for Europe. WHO–EURO report
and studies no. 78, Copenhagen, Denmark.

Program Guidelines

Step 1. A good sustainable maintenance program starts with proper identification of the stone. Is it granite, marble, terrazzo or limestone? If it’s marble is it soft or hard? What type of finish does it have? Polished, honed, flamed, etc.? Is the type of stone the proper material for the traffic it is to receive? If not maintenance costs will be higher. If the answer to these questions are unknown, I suggest you contact a reputable stone supplier or restoration company to find out. A complete understanding of your particular stones characteristics is an absolute must for designing a sustainable maintenance program.

Step 2. Once the stone’s characteristics are identified determine the quality of the installation. Are the tiles flat and even? Do they contain lippage (uneven tiles). If so, proper maintenance may prove difficult. The floor should be ground flat, honed and polished using sustainable restoration procedures that utilize non-chemical methods. Are there any cracked tiles? Dirt will have a tendency to accumulate in these cracks. These tiles should be replaced or if replacements are not available at least repaired.

Step 3. What is the present condition of the stone? Has it been coated with waxes, acrylics, urethane or other coatings? If so these coatings need to be ground off to determine the condition of the stone as well as eliminate any toxic and unsafe properties. I have seen stone floors that appear to be in great shape until the coatings are removed to unveil a pitted, scratched mess. If a poor condition is found, complete restoration is necessary before a successful sustainable maintenance program can begin.

Step 4. Once the stone is restored to like new condition, then and only then will a sustainable maintenance program provide good results. This applies not only to the following program but any program. If the stone will be exposed to water, coffee, spills etc, an application of a an approved Green impregnator is recommended. These impregnators are designed to penetrate into the stone, without leaving coatings on the surface and still allowing the stone to transpire(breathe). They contain no harmful vapors or off gases when cured.

Step 5. Daily Maintenance

The three most important tasks that can be done on a daily basis to keep the stone looking new and extending the time before restoration is required are: Dust Mop, Dust Mop and Dust Mop. The most destructive material to most stone is sand, dirt and miscellaneous grit. If these substances could be eliminated, maintenance of the stone would be almost non-existent. A stone floor can never be dust mopped too often. Use a clean, non-treated, dry dust mop at least two to three times a day in high traffic areas and less often in low traffic areas. Walk off mats placed outside and inside an entrance will also eliminate a good portion of sand, dirt and grit. It takes approximately seven steps to remove all loose dirt from the bottom of ones shoes. Walk off mats also need to be removed and cleaned daily. Keep this in mind when purchasing walk off mats. Remember if sand, dirt and grit are eliminated there will be nothing left behind to scratch and dull the stone.

Note: Coatings in addition to potentially being hazardous contribute to accelerate wearing of the stone or terrazzo surface by acting as a magnet for dirt and debri. It has been shown in studies that a stone or terrazzo floor without any coating will be easier to maintain as well as more cost effective.

Step 6. Cleaning

All natural stone, both polished and unpolished should be cleaned daily in high traffic areas and less often in lower traffic areas. A clean rayon or cotton string mop should be used with cold to warm water with the addition of a quality Green Approved neutral cleaner or stone soap. Approved Green Neutral cleaners are defined as surfactant type detergents that have a Ph of 7. Acidic and alkaline cleaners should not be used. Be sure to follow the directions very carefully.

Why Does Stone Shine?

All stone is taken from the earth in a raw block form. This block is cut into slices that we call slabs. The slabs are then cut further to a smaller size such as a tile or countertop. It is then polished using a series of abrasive materials. The mechanics are relatively simple. A piece of stone is rubbed with a series of abrasives starting with a course grit size followed by
Finer and finer grit sizes. The scratch pattern left behind from one grit is removed by the next grit creating finer and finer scratches. This process is continued until the scratch pattern becomes microscopic. The process is similar to refinishing a piece of wood, starting with a course sandpaper and ending with a fine sandpaper. The shine is placed on the stone by continuing this abrading process using very fine powders. With sustainable(Green) restoration methods no chemicals are used.


Periodically the stone will need to be restored. Perhaps you have not followed a proper maintenance program or the type of stone you have is not suited to the conditions it receives or for what ever other reason it is not responding to maintenance, then restoration is required. How often this will need to be done is difficult to determine. Generally if all the precautions above are followed, restoration may only be needed as often as once per year or as little as once every five years or so. The restoration process re-hones the stone to remove deep scratches and is then re-polished. Do not attempt the re-honing process yourself, this requires a great degree of skill and experience, please call a reputable restoration company who specializes in sustainable methods for this task.

Natural stone was the first building material used by man. Its care and maintenance is one of the oldest tasks performed by our ancestors and was maintained without any of today’s modern chemical products. The above guidelines were developed by our years of experience with this beautiful material and with the addition of sustainable practices will provide many years of beauty.

Written by

Frederick M. Hueston, PhD
Stone University
Web Site:

Thursday, December 6, 2007

How To Make a Slippery Floor Safe

How to make a slippery floor safe

There are many treatments that can be purchased and applied to a tile surface to make it slip resistant. These treatments fall into two categories: Coatings or treatments which chemically or physically alter the surface of the tile.

Coatings can be waxes, acrylics or other commercially available products. The coating places a thin layer of material on the surface of the tile. The tile will than be as slippery as the coating itself. Warning: not all coatings provide slip resistance. In fact some coatings will make a floor more slippery. Before specifying a coating, contact the manufacturer of the coating and ask for slip resistance test data. Many of the coating manufacturers are very familiar with slip resistance. Make sure the coating can be used on the tile surface you are using. Certain coatings will not adhere to polished stone or porcelain and require coatings specified for these surfaces.

There are now available special treatments that can be applied to the surface of tile to render it slip resistant. These treatments are primarily hydrofluoric acid. The acid attacks the surface of the tile and creates microscopic holes. This is what is typically called etching of the surface. This process works effectively on many surfaces but can decrease the service life of the tile. Once the surface is treated with this method maintenance will increase. Since these treatments contain a very dangerous acid, it should only be applied by trained individuals. Contact your local tile supply store for recommended contractors.

The issue of slip-resistance is of major concern in the US. Lawsuits are on the increase as con artists continue their search for the big payoff. Large hotels, banks and other big corporate building owners are their main targets but they are also targeting the small business. The corner food store and the local gas station are not exempt from these flim flam artists.
This is not to say that there are not times when a floor surface is not unsafe. Many factors contribute to the slipperiness of the floor. Water, grease, oil and debris scatted on the floor all can contribute to slipperiness. The competent architect and designer cannot control what happens to the floor after its installed but he/she can get it started properly.

How to Minimize Slip/Fall Accidents
Although it will be impossible to prevent all slip/fall accidents there are several precautionary procedures that building owners, cleaning companies and others can take to minimize risk. The following is some suggestions and is not intended to replace legal advise if an accident occurs:

1. Pay attention to areas where water and/or spills occur. A walk off mat should be placed inside the entrance of doors during a rain storm. When floor tile gets wet, the COF* may decrease causing a fall. Mats should be placed prior to the first drop of rain. Pay attention to areas where food is served or carried. Foods and drinks can create an ice like condition on the floor and any spills should be picked up as soon as they occur.

2. If the floor tile is maintained by stripping and waxing, this procedure should be done at night when there is no one around to fall. Daily wet mopping should also be performed at night during off hours.
*Coefficient of Friction
3. Always place wet floor signs in all areas you may be working in. This applies for all times of the day or night. It is also a good idea to train your floor cleaning personnel to warn people who may walk across the floor that it might be slippery.

4. Keep accurate records. It is surprising how many cleaning companies fail to keep any record of maintenance on a tile surface. Accurate record keeping says that you are responsible and that you generally care about safety. Include in your records the following information:
* Name brands of all products used on the floor

* Procedures that are performed on the floor and how often. Be specific.

* Who performed these procedures.

It is a good idea to keep a daily log of the maintenance procedure. Designate one individual to keep track of the log and have him perform routine inspections of the floor and record what he found during his inspections. If a legal suit is filed this information will be quite helpful in proving you are competent and hopefully not at fault.

5. Get slip/fall insurance. Every building owner should carry slip/fall insurance. Some of the products used on the floor will also carry slip/fall insurance. This insurance is designed to protect the coating manufacturer and you should not rely entirely on theirs. Get your own policy.

What to do when some falls:
O my, someone just slipped and fell, what should you do?

1. Treat the victim with kindness and courtesy. Do not administer medical treatment unless you happen to be qualified to. If necessary call an ambulance. Also offer to call their family. Show care and concern.

2. Look at the victim’s clothing and especially his/her shoes. Take notice of how worn they are and the overall condition. Once the victim leaves, record this information in your log or on a separate report. This is important, remember it takes two surfaces to slip, if the victim is wearing worn shoes part of the blame may be placed on their neglect.

3. Look carefully at the area where the victim fell. Is there water, grease, a banana peel? Record in the log any thing you find.

4. Did any one else see the fall. If so, take a statement from them. Record this in a special report and get their name, address and phone number.

5. Record the time and location of the fall. Pay special attention to the weather conditions. Was it raining, snowy or what.

6. Did you notice how the victim walked. Did he/she stumble or appear as if they were under the influence of alcohol or drugs. If possible record their behavior and how they walked or ran before the fall.

7. If you have a camera, take pictures of the victim and the area where they fell.

8. Fill out an accident report and do not leave out any detail. Use a separate sheet of paper if necessary.

Following the above suggestions will help considerably when involved in a slip/fall case. Your attorney will love you for it.

One Final Word

The legislation and rules concerning COF and slip/fall can and probably will change. It is a good idea to consult with an expert in slip/fall and to keep up to date with any new rule, law or recommendation that may sneak up

COF-Coefficient of Friction

Slip resistance is measured by the ratio of forces required to move one surface over the other under a given vertical force. In other words, it takes two surfaces to determine slip resistance. The floor tile is one surface and the bottom of ones shoe is the other surface. This ratio is what we call the coefficient of friction(COF).
COF can be measured in two different ways and can cause confusion amongst those unfamiliar with the science of slip resistance. When the COF is measured from a resting position it is called the “Static COF”. When it is measured when the surfaces are in relative motion it is called the “Dynamic COF”. The dynamic COF is very difficult to measure and almost all portable and laboratory meters measure only the static COF. It is important to know this difference since you will see both measurements in the literature. Most measuring devices(Slip meters) will refer to the static COF. The measurements you will find in the literature and those discussed here will be the Static COF. A COF of 0.5 is considered to be a slip resistance surface. The higher the COF the less slippery the surface. It is possible to have too high a COF. In other words the surface can be too slip resistance and an individual would find it difficult to walk on.

How to Measure Slip Resistance

There are basically two types of machines that can measure static COF, Permanent laboratory models and portable field models commonly refer to as pull meters. The most popular and widely accepted laboratory slip meter is the James Machine. The James Machine uses an 80 pound weight that is applied through an arm to a leather shoe placed on a panel. The panel and the leather shoe are moved horizontally. The distance the panel moves before slipping is measured and recorded on a chart and is the coefficient of friction. The James Machine was invented in 1940 and was the machine which established the 0.5 COF as the minimum for slip resistance. This standard was accepted in 1953 by the Federal Trade Commission . Many still consider the James Machine as the only true slip tester.

There are also many portable slip meters on the market which claim to measure the static COF. The American Society for Testing and Materials(ASTM) recognizes several portable meters. When purchasing these meters make sure they comply with ASTM C-1028 which is the recognized slip test for tile flooring. For further information on slip meters contact ASTM at the following address: 1916 Race Street, Philadelphia, PA 19103-1187

Written by

Frederick M. Hueston
The National Training Center for Stone & Masonry Trades


Epoxy vs Polyester for Stone Laminations

Epoxy vs. Polyester. Are You Using The Right Adhesive?
Frederick M. Hueston

I was sitting in my office when I received a call from a hotel manager about a swimming pool coping that was falling apart. I asked him what was falling apart and he told me that the stone was falling into the pool. I got in my truck and made my way over to the hotel and discovered that the swimming pool had a travertine coping and all the laminations where failing and falling off. I examined the laminations closely and discovered that Polyester was used in the laminations.

Several weeks later I got a similar call from a home owner who had a similar problem but this time the laminations where failing on her new granite countertop. Again, upon inspection, the adhesive used was polyester.

How many of you use polyester for your laminations and other applications where you are bonding two pieces of stone together? If you do, your laminations are prone to failure.

There are many choices when it comes to the selection of adhesives and it can get very confusing. The following is a brief explanation of the two most popular adhesives in the stone industry and a guide as to where to use what type:

Epoxy or Polyester?


Polyesters use a hardening agent to catalyze the curing reaction. Most polyesters use a peroxide hardening agent.

Of all the adhesives available polyester is the least inexpensive but also has the weakest bond strength. It also has a very high shrinkage rate and the highest water absorption amongst all the adhesives. It is also very prone to UV degradation and will crack and become brittle.

For this reason polyester should never be used for laminations or for repairs in wet area or used outdoors.

Polyesters are good for small repairs for indoor stone applications such as filling and seams or in applications where bond strength is of no concern. The bond strength of polyesters is less than 500 PSI.


Epoxies are two parts labeled part A and Part B. Most epoxies are mixed at a ratio of 2/1 but some are 1/1.

Of all the adhesives used in the stone industry epoxies have the strongest bond. Bond strengths can exceed 2000 PSI. It has a lower shrinkage rate than polyester and is more UV stable with a lower water absorption rate.

It is clear that if you want great adhesion, epoxy is the stronger adhesive. I always recommend using epoxy for laminations and rodding and anywhere else you want the stone to stick and not fall apart.

A little experiment.

Here is a crude test that I perform when testing adhesives for bond strength.
Take two pieces of stone with the polished sides facing each other. Place some adhesive on the polish faces and clamp them together. Let the clamped pieces set overnight. The next morning take a hammer and try to break them apart. A weak glue, such as polyester will break clean, leaving the face of the stone intact. A strong adhesive such as an epoxy will be so strong that the face of the stone will spall off. This indicates that the adhesive bond is stronger than the natural bond of the stone.

Adhesive Grades:

All adhesives are available in various viscosities ranging from low to high. The following are the most popular choices

Knife Grade- Consistency is similar to spackling putty or creamy peanut butter.

Flowing Grade- Consistency of a motor oil

Penetrating Grade- Consistency of water

Super Penetrating Grade- Consistency of a solvent such as mineral spirits or paint thinner

Generally knife grades are used for repairs for fills that are over 1/16 of an inch wide. Flowing grades are used for repairs smaller than 1/16th and for laminations and rodding.
Penetrating and super penetrating grades are rarely used by fabricators but are used for resining stone and for applications where an adhesive is need to penetrate very small pores.

Adhesive Colors

Today’s adhesives are available in a number of colors however there may times when you need to add coloring. Many of the adhesive manufacturers have tints that you can use. If you in a pinch I have found that artist oil colors work well for most polyesters, however for epoxies you will need to use tints designed specifically for them.

General Properties


All adhesives are sensitive to temperature and humidity. This means that cure times will vary. Adhesives will cure faster with increasing temperatures and slower at cooler temperatures.

Temperature will also affect the viscosity. Higher temperature will thin the adhesive.

Tip: There are several heated dispensers for epoxies that work very well for faster cure times and easier flowing.

Cure Time

The general rule of thumb for most adhesives is the slower the cure time the stronger the bond. Epoxies with a 7 hour cure time are going to be much stronger than an epoxy with a five minute cure time.
If too much hardener is added to polyester you will increase the cure time but you will reduce the bond strength.

UV exposure

Nothing is completely UV proof; however epoxies are more UV resistant than polyesters and are the adhesive of choice for outdoor exposure.


Polyester is very sensitive to moisture and for that reason it should be avoided in wet areas such as showers. Epoxy has a much higher tolerance for moisture and is the adhesive of choice in wet areas.

When using polyester you must make sure that the stone is completely dry. Epoxies can tolerate some moisture.

The stone must be completely dry
If you do not thoroughly mix the resin and hardener it will probably cure anyway
You can use most colors to tint
Many varieties available
Good adhesion when prepared properly
Can easily be used for patching
Stone surface must be abraded before sticking
Should NOT be used for exterior or in moist locations
Quick curing time (normally 10 minutes to 1 hour depending on the product and the weather)
Stone can be a little moist
Resin and hardener must be thoroughly mixed to cure
You should use only colors made for epoxy
Not as many varieties available
Great adhesions when prepared properly
Not as easily used for patching
Stone surface should be abraded, but it will stick to a smooth surface also
CAN be used for exterior and moist locations
Slow curing time (normally 7 hours depending on the product and the weather)

Use Chart

Laminations- Epoxy
Indoor repair- Polyester
Rodding- Epoxy
Outdoor Repair- Epoxy
Mending- Epoxy
Seams- Polyester
Attachments- Epoxy

Mr. Hueston is the founder of The National Training Center for Stone and Masonry Trades ( and Stone University (