How to Hire a Stone Restoration Contractor

RESTORATION & POLISHING

So your marble is dull, scratched and in major need of help! Out come the Yellow Pages; you call several marble refinishers and set up a few appointments. How hard can it be? You'll get a few estimates, check some references and select a professional to do the job. And then the fun begins. The first professional tells you that your floor needs to be ground flat in order to be fixed properly. The second professional tells you he can hone and polish it—no grinding required. The third professional tells you he only needs to recrystallize the marble to make it look like new. Now that you're totally confused, how do you determine who's right? What's the difference between grinding and honing? What are polishing and "recrystallization?" This report will arm you with enough knowledge of these terms to help you ask the right questions. Once you are familiar with the processes used to restore marble and stone, we will provide some guidelines and suggest some questions to ask the contractor.

WHY DOES STONE SHINE?

When stone becomes dull and scratched, it obviously loses its shine and luster. At this time the stone needs to be refinished and polished to restore the shine it had originally. Why does stone shine, and how can a lost shine be recovered?

All stone is taken from the earth in the form of raw blocks. Explosives, large saws and specialized equipment are used to extract the stone from the earth. The stone blocks are then cut into thinner, more easily handled pieces called slabs. The slab itself is then processed, depending on the intended use of the stone. It may be given a high shine and shipped to a marble fabricator, who will ultimately turn it into a table, vanity top or whatever; or it may be transformed by some very expensive and sophisticated equipment into tiles for installation on floors or walls.

The deep shine we see on polished stone is achieved by rubbing the stone with a series of abrasive materials. The process is very similar to sanding a piece of wood. The stone is rubbed with a coarse abrasive grit, followed by finer and finer grits until the stone becomes smooth. The scratches left behind from one grit are removed by the next, creating finer and finer scratches. The process continues until the scratches are microscopic. The shine on the stone is achieved by abrading the surface to the point at which it becomes extremely smooth and starts to develop some reflectivity. The shine on the stone is thus a product of optics. This same optical property can be observed on a pond. When the wind is blowing and the surface of the pond is wavy, it becomes difficult to see a reflection; when the air is still and the pond is calm, a deep reflection can be observed. So in order to achieve a deep shine on your stone, all that really needs to be done is to smooth it until it shines.

Sounds simple enough, doesn't it? Unfortunately, the techniques employed to achieve this degree of smoothness require special knowledge and training. This is not friendly territory for the do-it-yourselfer.

To help clear up the confusion, let's define some terms, then move on the the all-important issue of selecting a stone professional.

GRINDING

Grinding is the process by which the surface is aggressively sanded to remove large stocks of the stone. This process is usually recommended when stone tiles are uneven. Lippage is the term given to uneven tiles that are set higher than one another. Grinding is recommended when the lippage exceeds 1/8 inch or if one desires to have a completely flat floor.

There are some very good reasons for grinding a stone floor flat. A flat floor is easier to maintain; since there will be no lips where dirt can accumulate. The grinding process, if performed correctly, will also eliminate depressed grout joints—the grout will be even with the tile's surface so that dirt and grime can't accumulate. A completely flat floor eliminates all unevenness, giving the floor the illusion of being monolithic (one piece).

Note: a stone floor does not necessarily have to be ground to remove scratching. A skilled craftsmen can repair it without grinding.

Just as there are several good reasons for grinding, there are also some disadvantages. Grinding is very time-consuming and expensive; with some hard stones, like granite, it can take an entire day to grind 50 square feet. The grinding process is also very messy. Copious amounts of water are needed to grind a stone floor and produce a heavy slurry of stone and water. If adjacent areas such carpet, wallpaper, baseboards, etc., are not protected properly, water damage may occur.

Before deciding on grinding, all the above considerations must be carefully weighed. Discuss the options with the stone specialist.

HONING

Honing is the process of smoothing the stone with the use of abrasives. Although not as aggressive as grinding, it does require the use of water, and can also be quite messy. Honing is performed to remove scratches, and will not remove lippage (uneven tiles). It can, however, round the edges of the stone, giving a smoother finish to the edge. The honing process is usually achieved with the use of diamond abrasives, although some contractors prefer silicon-carbide bricks or screens. Which abrasive is used is not as important as the skill level of the craftsmen. Honing can leave a stone floor with very little shine, although some stones will acquire a satin-like luster at very high hones.

You may hear the contractor talk about grit sizes when discussing the honing-and-grinding process. The following table will serve as a guide to grit sizes. The lower the number, the more aggressive the grit. Generally, grinding is what takes place using any grit of 60 or below; honing begins at 120 and proceeds upwards. A skilled craftsman will generally stop at a 400 or 600 on marble before polishing. With granite, it is usually necessary to proceed through to the highest grit. Some craftsmen may choose to polish with diamond abrasives to the highest grit, producing a very high polish, while others may choose to switch from a diamond to a powdered abrasive (see next section). Whichever method is chosen, the final result is what counts.

GRIT SIZE TABLE

The following table list some of the most common grit sizes used in the stone industry. The lower the number, the more aggressive the grit.

16

24 Grinding

36

60

120

220

400

600 Honing/Polishing

800

1,800

2,000

3,000

3,500

5,000

8,500

POLISHING

As previously discussed, the high shine observed on stone is the result of smoothing it with fine abrasives. Most craftsmen will use diamond abrasives to hone the stone, then switch to a powdered abrasive to achieve the final polish. Powdered abrasives contain superfine crystals of aluminum oxide or tin oxide. These powders are usually white, but can be yellow, brown gray or black.

The abrasive powder is worked into the stone with a floor machine(buffer) using water and cloth or polyester fiber pads. The powder is worked into a slurry until a polish is achieved. The craftsman removes the slurry with a wet-vac or mop and rinses the floor to remove excess powder. It's a relatively simple procedure, but it requires a good deal of practice for several reasons. Many polishing powders contain a compound known as oxalic acid, which is used to speed the polishing process, and if too much powder is used, the stone can burn. A burned floor has a characteristic dimpled appearance; the stone will have a molten, plastic shine. This burned appearance is commonly called "orange peel," for reasons that are obvious to anyone who sees it. If the craftsmen orange-peels the floor, he will have to re-hone the floor to remove it. On the other hand, if too little powder is used, the final polish may not be achieved. A good craftsmen will be familiar with the powder polishing technique.

RECRYSTALLIZATION

The term recrystallization has entered the language of the marble polishing field to describe a process used to maintain a shine on marble surfaces. Recrystallization can also be called "vitrification" or incorrectly called "marble polishing." The procedure has been used in the United States since the 1970s, and has generated some controversy among the experts. Before we discuss the pros and cons of this process, we need to take a look at what it actually entails.

The recrystallization process consists of spraying a fluid onto the marble floor and buffing it in with steel wool under a standard buffing machine. The steel wool generates heat through abrasion and the chemical reacts with the marble, producing a new compound on the surface of the stone.

Sounds simple enough, so why the controversy? Proponents of the process claim the new compound formed protects the surface of the stone, adds shine and may even harden the stone, increasing its wear. Opponents of the process claim that the new compound that is formed blocks the stone's ability to "breathe," traps moisture and causes the stone to rot.

Both sides have put forward convincing arguments, but at this time, the jury's still out. If you opt for recrystallization, it is extremely important that the process be carried out only by trained craftsmen who are thoroughly familiar with it.

One additional note: the recrystallization process can only be applied to marble and limestone. Recrystallization cannot be used on granite, quartzite and sandstone.

WHICH PROCESS TO CHOOSE

It is very difficult for an untrained eye to evaluate your marble floor. Contact a reputable stone refinisher, ask the right questions and check references. The remainder of this report will offer guidelines to help you choose the right contractor.

HIRING A PROFESSIONAL

Hiring a professional stone contractor can be difficult. A careful reading of this report should give you enough background to know what a professional is talking about. Here are some points you should definitely cover before arriving at any decision:

1. Before calling any contractor, ask around. Have any of your neighbors had their marble/tile done recently? Who did it, and were they happy? Call your local stone/tile suppliers and ask whom they'd recommend for this type of work. Some of the stone/tile Associations may provide recommendations. And, of course, there are always the Yellow Pages.

2. Once you have located several companies, schedule appointments to receive estimates. Almost every contractor I know will perform a free estimate. Be sure you are there for the scheduled time; it can be very frustrating for a contractor to arrive for any estimate, only to find no one home. On the other hand, if the contractor fails to show for the scheduled appointment without at least calling, he obviously isn't interested in your project.

3. When the contractor arrives, explain what your concerns are and what you are trying to achieve. After all, you live with the floor every day; the contractor is seeing it for the first time. Give the contractor as much information as possible. What do you use to clean the floor? Has the floor been polished? Is there any wax or coating on the floor? If it's a new installation, the contractor will also need to know what materials are on the floor now. Any information will help him decide how to fix the problem.

4. Once the contractor has determined what is needed, ask him to explain the procedure he intends to use. Are there other options? Reread the section on restoration and polishing and ask specific questions. What polishing process will be used, etc.? A competent contractor should be more than happy to answer any question you may have.

5. A word on negotiating price: Among contractors, as in any occupation, personalities vary widely. Some contractors will negotiate; others will stick to their guns—although if you mention that you are getting two additional estimates, even a stubborn contractor may sharpen his pencil. Above all, make sure you're comparing apples to apples. If one contractor is only going to polish and the other is going to grind, the difference in price will be considerable.

6. If possible, obtain a demo or sample. Ask if a free demo can be performed; have it performed in a representative area. This will indicate what the final job will be like. Be reasonable, however; don't expect a contractor to perform a demo if the job is too small.

7. Ask for references—and check them. Many contractors in all fields have references, but you'd be surprised how rarely they are actually checked. Call at least three and ask if the contractor did a good job. Were there any problems and did he correct them? Where his employees professional?

8. Does the contractor carry insurance? Ask for proof. Have him show you a certificate of insurance, or, if the job is large enough, have his insurance company send you one. Be sure he carries liability and workers' compensation insurance. Any reputable company will carry both.

9. Once you choose a contractor, schedule the job. Don't be surprised if the contractor is booked for several weeks. Be patient; a good contractor will be busy, and you will have to wait your turn. If you absolutely must have it done now, ask him if he'll book you if he gets a cancellation.

10. Gut feeling—are you comfortable with the contractor? This is much more important than you might think.

Even the best contractors can make mistakes. The difference between a good contractor and a bad one is the willingness to correct those mistakes.

Removing Stains From Stone, Tile and Concrete

Oh, those nasty stains! How do you go about removing that red stain from the fruit drink your son spilled on the floor? What do you use to remove black marker ink from your white marble floor? Does lipstick stain? The list can go on and on.

Removing stains from marble, granite and ceramic tile can prove difficult. There are, however, several precautionary measures you can take:

Any spill should be cleaned as soon as possible. Blot spills with a paper towel or clean rag. At this stage, it is important only to blot; wiping a spill may spread it over a larger area, making a larger mess. Use only cold water and stone soap or a neutral cleaner. Rinse the area several times. If a stain is still present, a chemical poultice may have to be applied.

Avoid using chemicals of any kind until you know which chemical cleaner to use. Certain chemicals will react with the spilled material, and could make the stain permanent.

Marble, granite and certain ceramic tile are porous materials. If not thoroughly sealed, they will stain. The only way a stain can be removed is to literally pull it out of the stone or ceramic with both a chemical and material that will absorb the stain. This chemical absorbent-material combination is what we call a poultice.

Poultices are commonly powder or cloth materials that can be mixed with a chemical and placed on top of the stain. Refer to the table below for some of the more common poultice materials. Clays and diatomaceous earth are safe and readily available, but do not use whiting or clays containing iron with an acidic chemical; iron will react with the acid, and may cause rust staining. It is best to purchase powders that are designed specifically for stone and tile. Consult a stone restoration specialist or your stone supplier if in doubt.

Poultice materials:

Paper towels Cotton balls Gauze pads Clays such as attapulgite, kaolin, fuller's earth Talc Chalk (whiting) Sepiolite Diatomaceous earth Methyl cellulose Flour Saw dust How to apply a poultice

Before you attempt to remove a stain, it is extremely important to know what has caused it. If you don't know, I would recommend that you consult a stone specialist, or refer to my book on stain removal for a detailed description of the procedure.

To apply a poultice, take the following steps:

1. Clean the stained area with water and stone soap. Remember to blot rather than wipe.

2. Pre-wet the stained area with a little water. Distilled water is recommended.

3. Refer to the chart and determine which chemical to use for the stain.

4. Mix the poultice material with the selected chemical. Mix until a thick peanut-butter paste consistency is obtained.

5. Apply the paste to the stained area, overlapping the stain by at least ¼ . Do not make the application too thick, or it will take a long time to dry.

6. Cover the paste with a plastic sandwich bag or food wrap. Tape the plastic using a low-contact tape.

7. Allow the paste to sit for 12–24 hours.

8. Remove the plastic cover and check to see if the paste has dried. If it has not, allow it to sit uncovered until thoroughly dry.

9. Once it is dry, remove the paste by scraping and rinse the area.

10. Examine the stain. If it still remains, but is somewhat lighter, re-poultice until it is gone. If the stain refuses to disappear completely, it is time to give up, replace the tile or call a stone specialist.

Stain removal can be very difficult, and care must be taken when using a poultice. A complete guide can be found in my book on the subject.

For additional stains see out Stain Removal book or Stain Buster Guide.

White Powder On Floor

My new marble floor has a white powder on it. It cleans up with water, but keeps coming back. Is there anything I can use to clean it off permanently?

This is a common condition, especially if the floor is new. When the marble is installed, it is set in a mortar base that is wet; as the moisture leaves the mortar, it carries with it dissolved salts which are deposited on the surface of the stone. This condition, called efflorescene, is what you are seeing as a white powder. Unfortunately, every time you clean the floor with water you are only dissolving more salt in the stone, and when it dries, the salts return. To correct this problem, do not mop the floor with water. Either vacuum the powder or buff it off with a dry pad. The salts will eventually work themselves completely out of the stone.

Marble Polishing Problems

When I am polishing with a powder the marble gets a dull, wavy appearance and sometimes looks rough and dimpled. What's going on?

You are describing what is known as " orange peel". Orange peel is the result of using too much acid on the marble. In other words, most marble polishing powders contain acid and you are either using too much powder or working the powder too long. To remove the orange peel you will need to rehone the marble. When you start polishing apply a small amount and work it for several minutes, making sure to check it often by pulling the slurry back with a window squeegee. If a shine is not being produced, fight the urge to add more powder. First work the powder a little longer before adding more powder. This should prevent orange peel. If you should happen to orange peel the marble you will need to re-hone the marble to remove the dimpling. Orange peel cannot be removed with more powder. You will find that it is very easy to orange peel certain types of marble. Negro marquina, crema marfil and other soft marbles are easily orange peeled.

Marble or Granite?

I am building a new house and would like to use some type of stone for my kitchen countertops. Is marble or granite best?

Both marble and granite can be used for a kitchen counter but each has its advantages and disadvantages. Marble is available in an unlimited number of colors. It scratches very easily though. If you are going to be cutting meats and vegetables marble is a poor choice. Granite is very scratch resistant and will take cutting, however granite can be very porous and if you are doing a lot of cooking with hot oil, granite can stain easily. Granite can be protected against staining if you seal it with a good quality stone sealer. Most kitchen stone kitchen countertops are granite and overall is a good choice.

Granite Countertop Alert

There is a report circulating that granite countertops are unsafe, harbor bacteria and can produce disease. This is absolutely FALSE, NIOSH and the CDC have no reports of granite or any other stone used as a countertop as being unsafe. These rumors are being circulated by the Solid Surface Industry in an attempt to compete with the stone industry. Think about this for a moment, if stone was unsafe and unsanitary why would there be cutting boards sold made of stone. Why would stone be used in food laboratories. There has been no known proof of any illness caused by using stone as a countertop.

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Polishing Unfilled Travertine

Polishing unfilled travertine can be tricky. Polishing powders tend to accumulate in the holes and can make clean-up difficult. Try the following for easy polishing. To one gallon of distilled water add one pound of oxalic acid. Mix this solution and transfer to a spray bottle. Use this mixture to spray on the travertine and buff with a hogs hair pad. You will find polishing is a breeze. For more tips refer to our troubleshooting guide.

Is granite acid resistant?

WARNING-There is one acid that will severely etch, pit and dull a polished granite surface. This acid is known as Hydrofluoric acid(HF) and is found in many rust removers. If you have experienced etching on granite surfaces you may want to check the label and see if it contains Hydrofluoric acid. If it does, the granite may need to be repaired.

Black Granite Fading

I have received numerous calls lately concerning the fading of black granite counter tops. Why does black granite fade?

The answer is, black granite should not fade. Black granite imported from Asia is sometimes Doctored with dyes and oils to darken the surface. The fading is nothing more than the dyes and oils being removed. Unfortunately, the only fix is to re-polish the top. This can be costly.

Before purchasing a granite top perform the following test to find out if it has been doctored.

Take a clean white rag and apply a some acetone to the surface of the granite. If any residue or black color is observed on the top, do not accept it, it has been dyed.

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Marble Polishing Tip

Are you having trouble polishing marble? Try the following:

Instead of using a white polishing pad, try polishing with a high speed buffing pad. These pads are sold under many different names: Hogs hair, Gorilla, jacko, etc. These pads are designed for burnishing acrylic coatings, but seem to work great at slower speeds for marble polishing.

If you are still having trouble obtaining a high shine, try polishing until the powder/water mixture becomes dry and then continue polishing dry.

For more helpful tips see our troubleshooting guide.

REMOVING RUST FROM STONE SURFACES

Rust is one of the most difficult stains to remove from marble, granite and other stone surfaces. Many of the rust removers available in stores can damage stone. We have found a great method for removing rust stains.

A product called IRON OUT is available from most home centers and hardware stores. This product is a white powder that is designed for removing iron from water softeners, but also works great for removing iron and other metal stains from stone.

To remove iron stains mix I part IRON OUT to 2-part poultice powder (diatomaceous earth). Add water until you get a soupy consistency. Apply this mixture to the iron stain, cover with plastic and let it sit for 24 hours. After 24 hours remove the poultice and reapply if necessary.

For more information on iron stain removal and other stains see the book Stain Removal Guide for Stone, available from The National Training Center for Stone & Masonry Trades at 407-834-4800