Responsible Marble
Architects and Designers are specifying Marbles and Granites today more than ever. The popularity of dimensional stone has increased over 2000% in the last 10 years.
Unfortunately the end user is usually left uninformed as far as education of preservation maintenance, restoration, costs, etc. This leaves the customer feeling "ripped off" after a few short years and vowing to never use marble again (or the architect/designer who specified it).
These problems are what caused Ms. Mera Juestal-Parkin, corporate Executive Housekeeper for Hilton International to put a moratorium on any further use of marble floors and countertops until she could find out how to maintain them. She was fed up, and many others are too. If it keeps up, marble may well become a thing of the past once again.
This article is broken into four parts that are each as important as the next. All four parts should be considered before any new installation project is started.
I. Material specification
When specifying a stone, it is important to keep in mind a number of factors to help keep maintenance and restoration costs down.
Foot Traffic
If the floor is in a commercial building, the stone should have a high "abrasion resistance" rating (A.S.T.M.-C241) to deter scratches, and "compressive strength" (A.S.T.M.-C170) to deter chips and stuns caused by stilleto heals.
Finishes
Don't mix polished material finishes with honed. A restoration nightmare would be honed and polished pavers in a checkerboard pattern, or flamed granite with polished, etc.
Polished finishes on walls are easier to maintain than flamed or striated surfaces, and the finish doesn't require nearly as much maintenance as polished floors.
Patterns
Try not to mix granites and marbles or carbonate marble with serpentine marbles (Hydrated magnesium silicate). Both of these combinations could eliminate some of the most simple polishing methods, thus increasing maintenance costs.
Color
Dark colors (Red, Green, Black) show damage and scratches more obviously than light colors and will require more frequent maintenance program.
II. Installation Specifications
Of course, the preferred method for flooring installation is a mortar installation (mud set) with a bond coat.
This is now becoming the standard even in residential applications. With the introduction of 12"x12" pavers, ceramic tile setters started installing marble floors with thinset, which has excellent bond capabilities.
Unfortunately, thinset installations leave air pockets which can cause cracks, and thinset settles when it dries, causing lippage; A BIG maintenance problem.
Serpentine marbles should be set in epoxy or coated with polyester resin and dry set. This will keep the tiles from warping and breaking bond.
White marbles such as Carrara, Statuario Venato, Callacuttas, etc., should be sealed from behind with an impregnating sealer. This will keep the floor from yellowing due to the iron content of these stones activated by water and then rusting.
NEVER USE SANDED GROUT, or it may not be possible to resurface the floor. Always use a waterproof membrane over a concrete sub floor to keep moisture, rebar rust, mineral salts (efflorescence) from leaching up through the marble.
Specify an impregnating silicone sealer with a pre-treat on absorbent stone or honed finishes. Stone installations aren't complete until they have been sealed.
III. Restoration & Preservation
Grinding: Prior to a stone tile floor being ground flat, it can be very hard to maintain. The lippage and low grout joints tend to be places where dirt and mop water accumulate when the floor is being cleaned.
Floors with lippage should be vacuumed with a non-beater bar vacuum. The grinding process involves specialized tools and should be done by a qualified, well referenced, restoration contractor.
Diamond abrasive pads: This process is fairly easy to do, leaves a floor lippage free and is a fast and economical way to restore floors and countertops, the only downside to diamond grinding is that some floors can be left with a wavy look, but by using the right equipment this problem is eliminated.
Stone grinding: This process uses the same type stones used in the factories. The stones are fastened to specialized hand tools and floor machines. It is more time consuming and requires a higher level of expertise and muscle (the tools are very heavy) thus increasing the price. The end result is a mirror finish with no bumps or rolls.
Polishing: Once the floor is flattened and finished, maintaining that finish is fairly easy. Here are the two most common methods for maintenance polishing. These methods will take out fine acid etches and very fine scratches.
Powder Polishing: A metallic element power with oxalic acid and water create a slurry which is polished over the marble using a standard floor machine and a nylon pad. The slurry is then vacuumed up, then on to the next area or repeat area if necessary.
Power polishing changes the compostion of the top layer of marble to calcium oxalate which is of generally the same hardness as calcium carbonate and will allow the stone to breathe naturally. This method can be done as much as needed on most marbles, if the acid content is not to high.
Crystallization: This method a magnesium fluorosilicate acid is sprayed onto the floor surface and burnished into the marble using a specially designed and weighted floor machine and a steel wool pad.
It is a one man operation and is fairly easy to do. Crystallization changes the composition of the top layer of marble to calcium fluoride which is slightly harder than calcium carbonate.
This method is very popular and highly controversial. When used properly, this method can produce a very durable floor and a brilliant shine. It all hinges on the products used.
IV. Daily Maintenance
Dust mop as often as you can in residences; 3 times a day in commercial buildings. You can not dust mop enough--it is the single most important maintenance step you can take.
Mop as needed with a good marble cleaner or stone soap. I prefer soaps because they tend to keep the seal of the floor much better than detergents. Cleaners should be pH7 (neutral). Marble is alkaline, so no acids. Towel or buff dry after; drops of water that are allowed to sit can leave etch spots.
Acrylic polymer sealers or "sacrificial coatings" are designed to take the beating rather than the marble itself and are commonly used commercially.
The weakness with these coatings is that they are so soft that they have to constantly be stripped and re-applied, and the high alkalinity of these strippers harm the stone.
Some sealers yellow and can soak into the stone itself causing the stone to change color. The finish that acrylic coatings leave has an undesirable "painted on" look but is sometimes required by building managers to meet the strict new slip co-efficient standards set by the Dept. of Building and Safety.
These slip standards can be met by using the right kind of sealer (silicone impregnating) which sits below the surface of the stone and allows the natural beauty to shine through.
This about covers a little of everything in terms as "layman" as possible. I hope the information is this article is absorbed and taken seriously, if not for your own education and professionalism, but to protect the Marble industry itself.
Written by Michael Marsoun, 1994
