Efflorescence - Removal and Prevention

Efflorescence - Removal and Prevention

By Frederick M. Hueston, stoneforensics.com

The following article discusses historic masonry but the causes and principles are the same for any stone, brick or concrete surface.

The crystallization of soluble salts in Historic masonry causes severe deterioration of the substrate. This crystallization is called subflorescence. These salts are derived from several sources, including salts within the substrate, pollution, deicing salts and improper cleaning chemicals.  Problems associated with subflorescence can be diagnosed and identified by visual clues, such as spalling and rising damp.  Accurate diagnosis of subflorescence can be confirmed with laboratory testing. Once the salts are detected there are several methods which can remove these salts. Water washing, surface rendering and poulticing are a few of the methods used.  If these salts are successfully removed it is important to prevent reoccurrence. Preventative applications might include installation of dampproof barriers, chemical injection and coating the masonry with a sealer or impregnator.

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Subflorescence

 The deposit of water soluble salts in the pores of Historic masonry is the major cause for deterioration of these surfaces.  These salts originate from several sources.   Gauri, Holdren and Vaughan (1986) report that these salts are inherent in brick, concrete and natural stone.  Boyer(1986) contributes polluted rain water, roof salts, deicing salts and adjacent materials as the source of salt deposition.  Ashurst(1994) reports that careless cleaning using improper chemicals can deposit salts causing deterioration.   Regardless of the source all agree that water soluble salt deposition contributes significantly to the rapid deterioration of historic masonry.

Grimmer (1984) defines Subflorescence as follows:

Subflorescence is a potentially harmful accumulation, or build-up of soluble salts deposited under or just beneath the masonry surface as moisture in the wall evaporates.  Particularly during the freeze-thaw cycle, the moisture and salts in the wall freeze and expand, building up pressure within the masonry, which if sufficient, may cause parts of the outer surface to spall off or delaminate. (P. 22)

In other words, Subflorescence is the deposit of salt crystals beneath the surface of the masonry.

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Subflorescence and Efflorescence

Subflorescence should not be confused with efflorescence.  Efflorescence is a deposit of soluble salts on the surface of masonry. Efflorescence can be identified by a whitish haze on the surface of the masonry.  Efflorescence can be a precursor to subflorescence since its  indicates the presents of salts.  Efflorescence is common and often harmless on newly constructed buildings, but if it appears on historic masonry, it should serve as a warning that moisture has found a way into the masonry.

Diagnosing and Identifying Subflorescence

Subflorescence should be suspect when the following conditions are observed on a masonry surface:

1.  Spalling- Spalling of masonry surfaces can be identified by the breaking off of the surface layer. Small pieces of the outer layer will flake off in both small and large portions. Often the surface is very brittle and can easily be removed by prying with a knife. Spalling can also be called delamination when referring to manmade masonry.  The term delamination is general used for stone masonry.

2.  Rising Damp- Along the base of most masonry buildings, a wet, darken outline can be detected. This darkened area usually extends from the ground to several feet above the ground.  This darken is the result of water being carried through capillary action into the porous masonry. This condition is known as rising damp.  Rising damp can lead to efflorescence and ultimately subflorescence since salts can be dissolved and carried by the water.  Rising damp is a concern in Northern climates where deicing salts are used.  If the moisture remains during freezing months, the water will freeze, expand and cause spalling of the masonry surface.

3.  Post Cleaning Operations- Frequently masonry surfaces will develop efflorescence within several days after cleaning. The masonry surface should be checked carefully, since efflorescence can be a precursor to subflorescence.  This is especially troublesome if the cleaning operation used copious amounts of water.  Excessive use of water can saturate the masonry, dissolved salts within the masonr, causing spalling.

4. Chemical Cleaning Operations- Certain chemicals can deposit soluble salts within the pores of the masonry if not rinsed throughly.  Alkaline cleaning chemicals contain alkaline salts which can crystallize causing spalling of the masonry surface.  If spalling occurs shortly after cleaning check the type of cleaners used.

Testing for Soluble Salts

If soluble salts are suspected, a simple field test can be used to determine if salts are present. To determine the type of salts, thus leading to a possible source, laboratory tests must be conducted. The following describes these tests.

Field Testing- London (1988) describes a simple qualitative test for determining the presents of soluble salts using a protimeter.  The test uses the principle that dissolved salts have a higher capacity to conduct an electrical current.  A filter paper is saturated with distilled water, placed on a rubber block and a reading taken with the protimeter.  A second filter paper is saturated with distilled water, placed on the suspect masonry and a reading taken.  If the reading on the masonry is higher than the reading on the control, then soluble salts may be present. This test does have a margin of error and can be misleading. It is advised to verify with laboratory testing.

Laboratory Testing- Laboratory testing can determine quantitative as well as the exact identification of the salts.  It is important to know which type of salts are present in order to determine the origin.  Most all salts in historic masonry can be classified as follows:

Chlorides- Chloride salts are found in deicing salts. Ashurst (1988) also reports that chlorides can be hygroscopic, taking moisture directly from the atmosphere. Chlorides can also be found in high concentrations in environments near oceans and salt marshes. Chlorides can also be present in the make up of the masonry itself.

Nitrates- If nitrate salts are detected, ground water should be suspected. Nitrates are commonly found in fertilizers and in soils.

Carbonates- Carbonates are found in high concentrations in masonry mortars continuing lime. Carbonates are also present in pointing mortar and will usually present a problem when a building is repointed.

Sulfates- Sulfates are found in air pollution from vehicle exhaust, industrial pollutants etc. Sulfates are an increasing problem in areas where pollution is high.

Alkaline and Acid Salts- Alkaline and acid salts are deposited into historic masonry when cleaners are used and not rinsed probably. If efflorescence and/or subflorescence occurs shortly after cleaning, these salts should be suspect.  Hydrofluoric acid is commonly used to clean historic masonry since it is one of the few chemicals that do not deposit soluble salts(Ashurst, 1988).

Subflorescence

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Removal of Soluble Salts

Before any attempt is made to treat historic masonry and to remove both efflorescence and/or subflorescence it is necessary to find the origin of the salts. If this is not found, further damage may result.  Once the origin is found the first step in salt removal is to eliminate the source.

There are several methods for desalination of historic masonry. The following methods have proved successful but are not fool proof. It is vital that these procedures be performed by trained and experienced individuals.

Ashurst (1988) describes two possible procedures for removal of soluble salts, poulticing and sacrificial rendering.  Poulticing uses an absorbent clay mixed with distilled water into a paste.  This past is applied to the masonry, which has been saturated with water. As the clay dries it will absorb the moisture from the masonry carrying the salts with it.  Poulticing can be an effective treatment for removing soluble salts but caution must be exercised since salts can be drawn to the surface and crystallization may occur. Sacrificial Rendering uses an application of a thin coat of a lime and sand mixture.  This mixture is trowel on the wall as if applying stucco. The principle is that the rendering will absorb moisture and transfer the soluble salts to it.  Gauri et al (1986) describes two suction techniques for removal of soluble salts.  The suction method uses a vacuum pump attached to a funnel. The masonry is saturated with water and the vacuum pump pulls the moisture out with the soluble salts.  This method can be time consuming on larger surfaces but industrial equipment is available that can process several hundred square feet per day. Grimmer (1984) suggests the use of water washing to remove efflorescence.   The water washing method employs the use of water sprayed on the surface of the masonry. The water can be applied with

high pressure, low pressure, intermittent with an endless number of spray patterns. Water washing is the most common method employed for cleaning historic masonry but does have its shortcomings. Chemical cleaning is often used in an attempt to remove soluble salts with little to no result. Hydrofluoric acid is the most often used chemical on masonry surfaces.  The acid works by dissolving the salts which are rinsed away after a timed dwell period. Hydrofluoric acid also is damaging to the masonry itself since it dissolved the substrate.

Which ever method is used it is important to perform a test on the masonry and monitor it closely for any harmful effects.

Preventing Subflorescence

Damaging salts are carried into historic masonry by moisture. To prevent salt deposition it is necessary to eliminate the moisture. Grimmer (1984) suggests using a dampproof course. This dampproof course consists of placing a material such as plastic, horizontally in a masonry wall to prevent moisture from rising into the substrate.  Injecting chemical plastics into the masonry have also been used to eliminate moisture as well as the application of sealers and impregnators. 

Whichever preventive treatment is used it is important to remove the existing salts. This can be accomplished by the methods mentioned above or the masonry should be left alone and the salts allowed to migrate out. This is especially important with chemicals treatments. Sealers,

consolidants and impregnators should not be applied to masonry containing salts.  The application of these sealers, etc will prevent moisture from escaping, accelerating the chance of deterioration.

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Conclusions

The deterioration of Historic masonry through the crystallization of soluble salts is a growing problem in the preservation community. Improper cleaning techniques and air pollution both contribute to the build up of these salts.  It is important that the proper diagnosis be formulated so that further damage is not caused.  Desalination practices and procedure must be tested and performed by experience individuals.

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References

Ashurst, J.   (1988).     Practical Building Conservation.   New York: Halsted Press.

Ashurst, N.   (1994).    Cleaning Historic Buildings Volume I.   London: Donhead.

Boyer, D.W.   (1986).   Masonry Cleaning-The State of the Art.   American Society for Testing     and Materials.   25-51.

Gauri, K.L.   (1986).   Cleaning Efflorescence from Masonry.      American Society for Testing      and Materials.   3-13.

Grimmer, A.   (1984).    A Glossary of Historic Masonry Deterioration Problems and Preservation     Treatments.   Washington: Department of Interior.

London, M.   (1988).   How to Care for Old and Historic Brick and Stone.   Washington:     Preservation Press.

What’s Under Your Carpeting

What’s Under Your Carpeting

By Frederick M. Hueston. Stoneforensics.com

If your building was built prior to 1980  chances are you are hiding one of the most beautiful, elegant and sustainable floor materials. That material is known as Terrazzo.  Today, sustainability or what is more commonly known as Going Green is rapidly being required by many school systems, governments and private industry. Of all the materials  that can be used for flooring there are only a few that qualify as sustainable and are considered safe. They are stone and terrazzo.  However, even these materials can contribute to pollution and pose all kinds of health and safety risks if not properly cared for.

Why should you be concerned about your carpets and other flooring?  The General accounting office of the EPA reports that one of the top five health concerns is Indoor Air Quality. In addition they report that nearly 50% of the US schools have this problem.   

The following article will outline some of the hazards associated with other floor materials such as carpet and vinyl, as well as present a truly sustainable restoration and maintenance process for stone and terrazzo flooring. This information should help with your quest to improve indoor air quality in your school or building.

Carpet

Of the entire floor covering available carpet is the most popular and also the most hazardous. New and Old carpet alike emit harmful VOC’s (volatile organic Compounds) into the air. Solvents such as toluene, benzene, formaldehyde, ethyl benzene, styrene, acetone and the list goes on and on.  Carpets are also a great breeding ground for dust mites, fleas and other insects as well as toxic molds and mildew.  In addition carpet cleaning chemicals have been linked to diseases such as Kawasaki’s, fibromyologia and allergies.

Carpet in schools, offices and other public and private buildings are even more hazardous due to the number of people who not only walk on them but also people deposit skin cells, dust etc, not to mention food and drink that is spilled on them which provides the organic material necessary for bacteria to grow and thrive.

Of all the floor coverings carpet has the shortage service life.

Vinyl Composition Tile(VCT)

VCT is just as hazardous as carpet and possibly even more. The Adhesives used to attach VCT emit high levels of VOC’s. Since VCT is a tile moisture is often found between the tiles where toxic mold can grow.

VCT is found in almost all schools, government buildings etc. VCT is very inexpensive. VCT is made ( insert what it is made of here)

In addition to VCT composition almost all of it is maintained with harmful acrylic coatings. These coating need to be removed(stripped) and the strippers used contain hazardous chemicals as well(see article titled(Are Floor Strippers Safe). The Environmental Protection Agency(EPA) recommends that any major maintenance be performed only when the school is unoccupied for 48 hours.

Agglomerates

Agglomerated tile is composed of real stone fragments and polyester or epoxy resins. Some name brands include Fritz tile, Rover, Etc.  The manufacturing process uses synthetic resins that emit high amounts of VOC’s

Agglomerates are often maintained using the same hazardous coatings and strippers used on VCT

Terrazzo and Stone

Marble, Granite, limestone, slate and terrazzo are the only true sustainable floor coverings. Stone is all natural and contains no harmful VOC’s or any other hazardous elements. They are manufactured by mother earth and there fabrication uses only water and abrasives.  Terrazzo is composed of natural stone and Portland cement and is also very sustainable. In addition Natural Stone and Terrazzo flooring is long lasting. Just look at some of the buildings in Italy, France and other countries around the world. Some of these stone floors are hundreds of years old.

The dangers with stone and terrazzo floors come with the restoration and maintenance of these surfaces. Hazardous chemicals, polishes, sealers etc are often used for restoration and maintenance.  These chemicals are as hazardous as the waxes and strippers used on VCT and agglomerated floor coverings.

The good news is that Stone and Terrazzo flooring can be restored and maintained with no harmful or hazardous chemicals.  The restoration process uses only water and abrasives. Daily maintenance can be carried out using only Green Seal approved neutral cleaners.

If your floors are currently covered with carpet, vinyl etc.you may want to consider removing these harmful and dangerous floor coverings and restoring the terrazzo or stone that is under them.

Note: If you floors are not stone or terrazzo and are only concrete. Concrete can be polished and maintained as well.

The Stone Restoration Horizon is Changing. Are You Ready?

The Stone Restoration Horizon is Changing. Are You Ready?

By Frederick M. Hueston

Does old ever become new again? In the case of how stone restoration is done, the answer very well could be yes. I am referring to the polishing system for stone flooring that was used many years before chemicals came into existence, which is once again becoming the preferred method specified by more and more architects and others.  Why is this? Think “Green”. ‘Going green’ is rapidly becoming more and more prevalent everywhere and our industry is not excluded. I am finding that many projects across the US are now being specified with strict specifications that a green and sustainable restoration process be implemented for restoring both natural stone and terrazzo surfaces.  

What is Green?

There is an old Indian proverb that says something like, “We are not inheriting the earth from our forefathers. We are borrowing it from our children.”

As we hear more and more about the toll pollution takes on our environment, most of us are feeling some responsibility to do our part in saving our planet, not only for our present generation but for generations to follow. Everywhere you look, individuals, government agencies, universities and schools, and even private businesses are going green.

What Exactly Does Going Green Mean?

The term ‘green’ or ‘going green’ is a term we hear frequently these days, but few really know what the term means. Going green can be aptly defined as 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 as well as individuals feel that they are too insignificant to make any impact on the environment. If this is the way you think, consider the following:

·       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.

Can Stone Restoration Go Green?

Traditionally the restoration, repair and maintenance of stone and terrazzo surfaces are anything but ‘green’. We use chemicals that are harmful to the environment and to people in general. Chemicals such as polishing compounds contain 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 copious amount of waste and use large amounts of fresh water. Can such a non-green process be completely transformed into a green one?

The answer is a resounding yes. I am currently working in a cooperative effort with several stone restoration companies that are on the leading edge in ‘going green.’ They are actively and continually developing methods to eliminate all of these harmful chemicals and processes from their services. 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 that comes off and gets left behind on the floor. The diamond abrasive is fixed to a pad. There are no chemicals used at all.

The water used is recycled and reused in a specially designed system.

Superfine abrasives are then used to polish the stone or terrazzo. These abrasives contain no harmful chemicals.

This green stone and terrazzo restoration process has no negative impact on the building environment or the occupants since no chemicals or topical finishes are used. The maintenance requirement after the stone or terrazzo is restored is reduced by as much as 50% or more thus reducing additional costs on labor and chemicals.

In addition to traditional diamond abrasives there are companies such as Innovative Surfaces Solutions(http://www.innovativesurfacesolutions.com/) that manufacture pads that are chemical free and achieve the same results.

The Advantages of a Chemical-less Process Go Beyond Going Green

Many stone restoration and janitorial companies use chemical topical finishes to achieve a high luster on stone or terrazzo floors. Not only do these finishes contain chemicals that are harmful to the environment, they also have a negative impact on the aesthetics of the surface. 

Most finishes used on stone and terrazzo are soft and tend to show wear and scuff marks in a very short time. This increases 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 that 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 personally conducted experiments that prove that a coated surface will attract more dirt than a surface restored using chemical topical coatings.

OBJECTIONS

There are many professional stone restoration companies and others who will object to the viability that stone can be restored, polished or maintained without some chemical procedure. So what are the objections?

Stone Cannot Be Polished Without the Use of Chemicals.

Many stone restoration companies will argue that it is impossible to achieve a deep clarity and high reflection on natural stone without the use of chemical polishes.

This is simply 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. There are several great examples of this. Syracuse International Airport and Chicago OHare are two great examples of sustainable polish. I have worked with several school systems that have their terrazzo floors polished with this method very successfully.

It Costs More To Go Green.

Again this is not true. As a matter of fact going green may cost a lot less. This is especially true after the stone is restored and needs to be maintained. An independent study shows that the return on investment is realized in under 3 years with a savings of around $1.85 per square foot per year.

As A Small Contractor I Can’t Afford The Large Machines Necessary To Do This Work.

This is a valid argument I’m afraid. It does take large machinery that is in fact expensive. Furthermore, for small residential and commercial projects these large machines will be impractical. However, with that said, be aware that technology is advancing and there are now diamond abrasives that will achieve a polish equal to or greater than a polish achieved by chemical methods.

I am old enough to remember when there used to be small corner grocery stores all over the US. Today the large chains have put these small stores out of business. I’m afraid this is what will happen to the small contractor if they don’t keep up with current methods and seek to develop sustainable methods to compete with the larger companies.

Even With Small to Medium Hotels, etc., It Is Impossible To Use 220 V Or Three Phase Machines Since They Will Require A Large Generator That Is Too Noisy For These Facilities.

Again, I cannot agree more with this. But, there are propane powered machines available that are quiet and are rated by EPA and OSHA for use indoors. I know of several contractors who are using these machines and methods very successfully in small to medium size buildings.

A Word of Caution: Be Wary of Green Washing                                                                                                                                       

Be leery when looking at a “green” product claim. Many chemical companies have reduced the percentage of hazardous chemicals in their formulations and call it ‘green.’ 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 an article by The Environmental Working  Group (www.ewg.org/schoolcleaningsupplies), which uses the cleaner Simple Green as an example. The article states that Simple Green claims to be non-toxic and biodegradable but fails to mention that the principal cleaning ingredient it contains is a possible human carcinogen. The hazardous ingredient is still present along with all the dangers it exhibits. To be totally sustainable it is best to use NO CHEMICALS at all.

In Conclusion…

Times are changing and technology is advancing. Higher demand for sustainability is fast approaching and in no time it will be required in many states. Yale University has already put policies into place that ban the use of any chemicals for not only restoration but for maintenance. Several states now have legislation in place that will mandate that sustainable methods be used in maintaining flooring surfaces.

The small contractor that fails to be prepared for the future just may find themselves zapped back to the stone age and struggling like a caveman hunting for his next job.

What Can You Do?

Be on the lookout for stone restoration training programs to include ‘going green’ processes. The Stone and Tile School (www.thestoneandtileschool.com) is now incorporating an introduction to ‘going green’ in its stone restoration training and will be announcing courses on this soon. 

Fred Hueston, , is the Director of Stone Forensics (www.stoneforensics.com); Chief Technical Director for Stone and Tile PROS, Inc. (www.stoneandtilepros.com), and is an instructor for The Stone and Tile School where he teaches advanced courses.

Stone and Tile Floor Damaged from Hurricanes and Floods? Replace or Repair

Stone and Tile Floor Damaged from Hurricanes and Floods? Replace or Repair
By Frederick M. Hueston

Attorneys and Insurance adjusters have difficulty in cases where flooding occurs due to the fact that it is difficult to determine if a floor needs to be replaced or if it can be repaired. This is going to be a question that will need to be answered in light of Harvey and Irma, the recent Hurricane
that hit the South. To determine the extent of damage and to ultimately settle on a value for the claim a throughout understanding of what can cause these damages is necessary. The following article will help you understand what can happen when a stone or tile floor is flooded. As an expert witness I have been involved in many cases where flooding is an issue. Many times the wrong process is used for cleaning which can cause greater, and perhaps irreversible, damage to the floor.
In addition many insurance companies will not pay claims due to the lack of visual evidence and will sign off on a claim only to find that
additional underlying problems didn’t manifest visually until months afterward. If you have a client or represent an insurance company, please contact an expert who is thoroughly familiar with these types of issues and can help with your case.

Flooding can wreak havoc on natural stone and tile floors. Flood waters not only contain water which can harm and destroy marble, granite,
limestone, terrazzo, and tile flooring, but they also contain debris and dirt as well as other harmful contaminates that can cause staining and other problems. Many times the damage that is done by the flooding will not show up until months later.

As a stone forensic expert I deal with problems such as those resulting from flooding on a frequent basis. The good news is that not
all of the problems that result necessarily mean the floor must be replaced. There are some tests that can be performed by forensic experts to see if it is possible to reverse the damage rather than having to resort to costly replacement.

Following are some of the most common problems that may
occur.

Efflorescence
Efflorescence appears as a white powdery residue on the surface of the stone. It is a common condition on stone, terrazzo, and tile installations
when the stone is exposed to a large quantity of water, such as flooding. This powder is a mineral salt from the setting bed. It can be removed by cleaning professionals but many times will come back after the initial cleaning. The stone will continue to effloresce until it is completely dry. This drying process can take several days to many months. A major mistake that is often made—even by some professionals—is to apply a sealer to the stone or tile. The reason this is a major mistake is the sealer will block the escape of moisture which can cause further problems such as flaking and spalling of the stone.

The stone or tile should be evaluated for moisture by a professional stone and tile forensic expert to determine the extent of residual
moisture.

Sub-florescence
Sub-florescence 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 salts are deposited on the surface of the stone. In sub-florescence, 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. Sub-florescence is very common on green marbles and on almost all stone and tile surfaces where flooding has occurred. The stone or tile can be tested for salts by a qualified professional stone and tile expert.

Yellowing and Discoloration
Many light colored stones 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 as from a flood. 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 marbles suddenly turn yellow. The process is difficult to reverse and replacement of the stone may be necessary if not properly evaluated and the proper removal technique.

Warping
Several types of thin stone tiles are very susceptible to warping when exposed to flooding. Many of the green marbles and a few
agglomerate marbles are notorious for this warping condition. Many installers have had the surprise of finding that their tile installation has mysteriously 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 stone’s crystal changes and causes it to warp. Whatever the reason, one thing is for sure, green marble can warp when set with water based materials or exposed to copious amounts of water.

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. In order to determine if the stone can be repaired a
detailed investigation must be made. This many include removing a tile to determine the type of setting bed, etc.

Erosion
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 urge you not to specify 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.

Hollow Sounds
I constantly get calls from insurance adjusters, contractors, attorneys, etc. about hollow sounds that occur after a floor has
been exposed to flooding. The fact is those hollow sounds that occur on a floor are NOT caused by flooding. The reason is simple:
most setting materials are made from Portland cement. It is a well-known fact that Portland cement has hydraulic properties. In other words, it cures in the presences of water. If your client is complaining about hollow sounds and is trying to blame it on a flood, keep this
in mind. An inspection and evaluation of the floor is necessary to determine the extent of the hollow sounds which can cause deboning and other issues.

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 stairs, water fountains, interior floors and other areas where stone is exposed to flooding. The crusts are a deposit of hard mineral salts consisting of calcium and magnesium. These minerals originate from 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.

Conclusion
Having a stone or tile floor that has been subjected to flooding evaluated by an expert is highly recommended. It may make all the difference. For example, white marble can turn yellow months after the flood. Tiles can become cracked due to swollen subfloors that are not visible to the naked eye, etc etc.
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contact Stone Forensics at www.stoneforensics.com for an inspection

Copyright 2017 Stone Forensics

Stone Impregnating Sealers are not Bullet Proof

Stone Impregnating Sealers are not Bullet Proof

By Frederick M. Hueston, stoneforensics.com

I receive several calls a week with questions on the use of impregnating type sealers for use on outdoor stone as well as interior wet areas such as showers, water fountains etc. The question is simple: Should I seal my stone in these conditions. The following article will provide a reason why stone in wet areas should not be sealed.

Before we discuss the reason why we shouldn’t stone in these conditions a few definitions are necessary

Impregnators or 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. Most impregnators are vapor permeable.

Vapor Permeable:  breathability, vapor permeability describes a stones ability to allow water vapor to pass through it.

The case for not sealing stone in wet environments

When stone is exposed to unregulated humidity and temperature fluctuations, like it would in an outdoor environment or in a shower the air contains vapor in what we know as humidity. Temperature along with humidity can result in condensation as well.

Most of the impregnators on the market today our breathable. This simple means that the stone will be protected from water entering the pores of the stone in liquid form but will allow water vapor to pass.

In an wet environments vapor can be present for several reason, rain, high humidity, temperature fluctuations, steam etc. Since these impregnators are breathable this vapor can easily penetrate into the stone.  One would think that this is a  positive. The fact is that once the vapor enters the stone it can condense and become a liquid. Since impregnators protect against water in its liquid phase it becomes trapped within the stones pores and will not escape until it evaporates or in other words turns into a vapor. Once this water becomes trapped it can result in all kinds of problems. Stones with iron content can begin to oxidize, natural salts with in the stone can become dissolved and cause pitting and spalling. Aesthetically the stone will appear darker since it is constantly wet.

This problem is becoming more of an issue with the increase of stone being used in showers and exterior environments. There are currently several people doing experiments demonstrate that sealer in wet environments can cause these issues.  I strongly believe that care should be taken when sealing stone in these wet environments.

Stain Removal Procedure for Stone Surfaces

Stain Removal Procedure for Stone Surfaces

By Frederick M. Hueston , www.stoneforensics.com

If you find that there are some stains on your stone flooring the following stain removal information should help you remove them. A video on this procedure can also be found at http://www.youtube.com/watch?v=kh0_tUphEco

Poulticing Materials:

I have found that most stains can be classified into one of the following categories:

Oil-Based Stains: Grease, tar, cooking oil and food stains.
Organic Stains: Coffee, tea, fruit, tobacco, cosmetics, etc.
Metal Stains: Iron (rust), copper, bronze, etc.
Biological Stains: Algae, mildew, lichens, etc.
Ink Stains: Magic marker, pen, ink, etc.

There are, of course, other materials that will cause staining. These five categories are the most common.

Applying the Poultice

Once the stain is identified, the following steps can be followed:

1. Wet the stained area with distilled water. Pre-wetting fills the pores of the stone with water isolating the stain and accelerating the removal by the chemical.

2. Prepare the poultice. If a powder is to be used, pre mix the powder and the chemical of choice into a thick paste, the consistency of peanut butter. In other words, wet it enough so that it does not run. If a paper poultice is to be used, soak the paper in the chemical. Lift the paper out of the chemical until it stops dripping.

3, Apply the poultice to the stain being careful not to spill any on the non stained areas. Apply approximately 1/4-inch thick over-lapping the stain area by about one inch.

4. Cover the poultice with plastic (food wrap works great). Tape the plastic down to seal the edges. It also helps to poke several small holes in the plastic so that the powder will dry out. Failure to do this may result in the poultice staying wet.

5. Allow the poultice to dry thoroughly. This is a very important step. The drying of the poultice is what pulls the stain from the stone into the poultice material. If the poultice is not allowed to dry, the stain may not be removed. Drying usually takes from 24 to 48 hours.

6. Remove the poultice from the stain. Rinse with distilled water and buff dry with a soft cloth. If the stain is not removed, apply the poultice again. It may take up to five applications for difficult stains.

Some chemicals may etch marble and limestone surfaces. If this occurs, then apply polishing powder and buff with a piece of burlap to restore the shine.

Poulticing Powders:

Clays (Attapulgite, Kaolin, Fullers earth)  DO NOT USE OF RUST STAINS
Talc
Chalk (whiting)
Sepiolite (hydrous magnesium silicate)
Diatomaceous Earth
Methyl Cellulose
Clays and diatomaceous earth are usually the best. Do not use whiting or iron-type clays, such as Fullers Earth, with acidic chemicals. They will react with the material, canceling the effect of the poultice.

Many stains are so deeply imbedded that the poultice alone will not be completely effective. Some type of chemical solution will need to be added to the poultice. When the poultice and chemical are applied, the chemical is absorbed into the stone. The chemical reacts with the stain and is re-absorbed into the powder/material.

Stain Removing Chemicals

How do you choose the proper chemical for a given stain?

First, you need to identify the stain. This is the most important step in stain removal. If you know what caused the stain, you can easily look at a stain removal chart for the proper chemical to apply. If the stain is unknown, then you need to play detective. Try what caused the stain. If the stain is near a plant container, it might be that the plant was over watered and the soil has leached iron onto the stone. The color of the stain may help to identify the cause. Brownish color stains may be iron (rust) stains. The shape or the pattern of the stain may be helpful. Small droplet size spots leading from the coffeepot to someone's desk are a sure giveaway. Do some investigating and use your powers of observation. This will almost always lead to the identification of the cause of the stain.

If, after thorough investigation, you still have no idea what the stain is, then you will need to perform a patch test. A patch test simply means applying several chemical poultices to determine which will remove the stain.

There are also pre-prepared poultice mixes that have the chemicals already added. All you have to do is add water.

One way to reduce the amount of staining on any stone surface is to make sure it is sealed with a good penetrating sealer or impregnator.

Stain Removal Guide

Iron (rust) - Poultice with Iron Out + Powder + Water.  (Iron Out is available at hardware stores). Both mixtures may etch polished marble, so re polishing will be necessary.
Ink - Poultice with Mineral Spirits or Methylene Chloride +Powder.
Oil - Poultice with Ammonia+ Powder Methylene Chloride can also be used on tough oil stains.
Coffee, Tea & Food - Poultice with 20 percent Hydrogen Peroxide + Powder.
Copper - Poultice with Ammonium Chloride + Powder
Paint (water-based) - poultice with a commercial paint remover + Powder
Paint (oil) Poultice with Mineral Spirits + Powder. Deep stains may require Methylene Chloride.

Please use extra caution when handling all chemicals listed above. Thoroughly read Material Safety Data Sheets for each chemical before use.

Stone impregnating sealers in wet environments? Bad idea.

Stone impregnating sealers in wet environments? Bad idea.
By Frederick M. Hueston, stoneforensics.com

I receive several calls a week with questions regarding impregnating-type sealers for use on outdoor stone, as well as interior wet areas, such as showers, water fountains, etc. The question is simple: Should I seal my stone in these conditions? The following article explains why stone in wet areas should not be sealed.

About Penetrating Sealers

Penetrating sealers, or impregnators are designed to penetrate below the surface of the stone and deposit solid particles into the pores of the stone and coat the individual minerals below the surface of the stone. With the pores filled, water, oil, and dirt are restricted from entering the stone. Impregnators can be solvent or water based, and most impregnators are vapor permeable or breathable, which means water vapor is able to pass through the sealed stone.

Why not seal stone in wet environments?

Although most impregnators on the market today our breathable, this does not mean they are suitable for wet environments. Stone sealed with a penetrating sealer is protected from water entering the pores of the stone in liquid form, but these sealers will still allow water vapor in the form of humidity, steam, and other forms to pass into the stone. Moisture absorption inevitably occurs when stone is exposed to unregulated humidity, temperature fluctuations, and the like.

Once vapor enters stone, it can condense and become a liquid. Since impregnators form a protective barrier against water in its liquid phase, this condensation-turned-liquid becomes trapped within the stone's pores. It will not escape unless it returns to its vapor form and evaporates.

Trapped liquid can result in all kinds of stone problems. Stones with iron content can oxidize, which means the iron can rust and discolor the stone. Natural salts within the stone can dissolve and cause small holes called pitting or flaking of the stone's outer layer, called spalling. Aesthetically, the constantly saturated stone will appear darker than its natural brightness. 

Research Continues, But In The Meantime...

With the surge of stone installations in showers and exterior environments in recent years, problems associated with stone sealed with impregnators are becoming increasingly prevalent. Researchers are continuing to experiment and making a strong case that sealing stone in wet environments is inadvisable. I strongly believe that careful consideration should be taken before sealing stone in wet environments.