Educating with Misinformation

Staff

In the August 2005 issue of Consumer Reports Magazine, the misinformation pertaining to natural stone that is—unfortunately—so ubiquitous, was inadvertently perpetuated further.

The editorial, Countertops, Stylish and strong, which was included as a sub-section within an article entitled, Bathroom Makeovers, Relaxing retreats for less was dedicated to countertops for both kitchen and bath and identified, reviewed and rated the materials commonly used for such, specifically engineered stone, granite, ceramic tile, stainless steel, laminate, solid surfacing, marble, concrete, and limestone.

Unfortunately, the testing itself was flawed for two reasons by no fault of Consumer Reports. One, the information on which their ratings and recommendations were based, derived from people in the industry, was incomplete and thus resulted in erroneous conclusions—ranging from a blanket statement that all granite needs to be sealed periodically to overly generalized statements regarding limestone that could very well impact a consumer's choice.

Secondly, problems that would qualify as significant considerations for consumers could not be achieved in a laboratory setting over a period of what was presumably only a few days at best. For example, engineered stone, which came out ranking just a hair higher than granite (only due to granite's need to be sealed periodically) has a sensitivity to UV rays over a certain period of time, as well as values of thermal expansion that far exceed those of natural stone. The latter can lead to seam failures that cannot be rectified in a permanent way. Furthermore, engineered stone was accurately rated as “stain resistant” but, as you well know, that doesn’t mean “stain proof.” We have reports (only a few, but significant) from users of engineered stones that are experiencing staining. Keep in mind that even the best manmade product is subject to differences in production, and certain batches may not be as good as others. This is without mentioning that there are different makers of engineered stone, and they all have— even if so slight— different manufacturing processes that could make a difference in the performance of the final product. This is not to say that engineered stone is not a great product. It is an excellent product. But, consumers should have been given the whole story.

Marblecleaning.org responded to the editors of Consumer Reports with the following letter:

Dear Editors:

Making reference to your editorial on materials for countertops (Countertops, Stylish and Strong, Aug. 2005), we at marblecleaning.org feel compelled to respond—specifically with regard to the way you classified the natural stones you mentioned, namely limestone, marble and granite, and your blanket recommendations. Due to the inherent complexity of the subject—natural stone—blanket statements cannot apply and are therefore inaccurate and misleading.

Let’s take limestone first. How many different types of limestone had you tested? The word limestone means very little—if anything at all. There is limestone that is quite dense and virtually liquid proof (it does not require any sealing), as well as acid resistant, while at the other end of the spectrum is limestone that literally crumbles under running warm water. Consequently, while the first type of limestone would qualify as a terrific material for a shower stall, one would not want to have the latter installed in the same place. There are literally hundreds of different limestones with a broad range of characteristics.

The same thing applies to marble. For starters, true geological marble is a minority. Most of the marbles on the market are in fact compact limestone. Then there are dolomitic marbles, aragonite-based marbles, serpentine, ophicalcite, etc., all traded under the generic classification of marble. All these different rocks can be quite different in performance and maintenance requirements. However, contrary to widespread popular misconception, the “average” marble—especially in its polished version—is quite a dense stone and seldom requires the application of a penetrating sealer, because stains (true stains, that is) are a rare occurrence. The polishing process takes care of making the pores on the surface of the stone very tight and almost liquid-proof.

The most common and disturbing problem with most marbles is their sensitivity to pH active liquids—mostly acidic. The calcium carbonate, which is the main component of most marbles, will chemically react with any acid you can think of, the consequence of which is that a “water spot” or a “water ring” will appear. No matter what they look like, these are not stains and they were certainly not caused by water. They are in fact a mark of corrosion, or acid burn, a.k.a. etching—in a nutshell, surface damages. No sealer for stone in the entire planet could do the first thing to prevent those damages, which are strictly related to the chemistry of the stone, not its absorbency rate. Hence, polished marble—with the exceptions of those that are acid resistant, such as dolomitic marbles and serpentine—should not be installed in a kitchen where acidic spills are a common occurrence.

As for granite, approximately 95% of all the stone traded as granite may not be even remotely related to granite and to each other. Just putting one label to a whole bunch af different stones doesn’t make those stones what the label says, does it? For example, the stone that you display in the picture is garnet gneiss—a far cry from geological granite. By broad acceptance they could be classified as “mercantile granites” (whatever that means), but this broad label could not, and in fact does not accurately represent the actual huge geological differences between all those stones and the differences in performance and maintenance requirements, specifically the need to apply a sealer periodically as stated in your article.

The physical and chemical characteristics of stones traded as "granite" can be, and often are, miles apart. Many of these stones, such as Gabbro, Dolerite, Anorthosite, Charnockite among others are inherently so dense that they will not even take in any sealer and critical to this topic, it often happens that if one seals them anyway they may develop problems in the form of weird “ghost stains” that would never have appeared if sealer had not been applied to the stone.

Therefore, your generalized statement that all granite needs to be periodically sealed is inaccurate and misleading information. Furthermore, even stones such as the one you have in the picture, which is naturally very absorbent and does require periodic sealing, may not require it at all if the slab had been resined by the factory. Such [resining] process is becoming more and more popular and takes problematic “granites” and makes them just as impervious as engineered stone, while preserving their unparalleled beauty and other positive aspects of natural stone.

Petrography is a very complex and vast science and simplistic classifications meant to “keep things simple” ends up creating a lot of unnecessary confusion. Petrography cannot be accurately summarized in a simple blanket statement. Unfortunately, it too often is, which is in part why marblecleaning.org was formed.

Marbleclecleaning.org is strictly a consumer advocacy and information source. It has no commercial agenda whatsoever. In fact, among our panel of experts, all of which are internationally recognized stone maintenance/restoration professionals, none is even laterally involved in selling stone and/or stone alternative. Our mission is two-fold—to represent the voice of the consumer to effect much needed change in the highly unregulated natural stone industry and to be a rich resource of credible information. Each of the experts on our "Ask the Stone Experts," several of which are sought after writers and lecturers in addition to running their respective restoration businesses, volunteers their time and knowledge derived from years of practical experience and extensive on-going education, to provide answers to consumers that write in.

The team at MarbleCleaning.org