Crema Bordeaux (top) and Santa Cecilia, half untouched, half sealed with HMK S34 Silicone ImpregnatorIf you’ve been in the dimensional stone industry for any amount of time, this familiar question seems to pop up with great regularity.

Among experts there seems to be some disagreement. Manufacturers of competing quartz products make quite a bit about the need to seal granite with advertisements boasting, “Quartz never needs to be sealed.”

So, what is the truth? If you turn to The Marble Institute’s website on the topic, they offer in the opening sentence, “Most granite countertops do not need to be sealed.” ( Reading further in the article, it states, “In many cases it makes sense to seal marble and granite...,” and the closing sentence seems to seal the deal (pun intended), “Sealing resin treated countertops may increase the resistance of the already resistant nature of stone.”

My first reaction in reading this statement was that this seemed to be a bit squishy– not the definitive statement I was looking for. As stone professionals, we need to have authoritative facts that we can assess to form our own solid conclusions.

To find the answer I turned to the source; I contacted TenaxUSA, the world leader in chemicals for the stone industry, and the largest producer of resins for treating granite slabs. I spoke with Mr. Domenico Borelli, Sales Director for North America. We had quite a lengthy and informative discussion on the topic. As well, though I was quite familiar with Tenax the company, I learned a great deal more about this industry leader. Before I get to the guts of the matter regarding sealing granite, consider the following about Tenax, SPA.

Founded in 1956 near Verona Italy, Tenax began making mastic for the stone industry. They also produced synthetic abrasives for marble production. Tenax quickly proved to be an industry leader and has grown into an international business with seven branch offices and 300 employees worldwide.

Santa Cecilia sampleWith more than forty experts in Brazil alone, they visit quarries and hundreds of factories assisting fabricators with selecting the right components from their more than 250 epoxy “systems.” These systems are selected based on numerous criteria including: yield enhancement, reinforcement, color enhancement, production time constraints, and many more criteria based on the nature of the stone, specific quarrying problems, sawing problems, appearance and strength issues.

With engineers on the ground, in quarries and factories, backed by their laboratory technicians, Tenax can prescribe a specific product to provide very specific solutions to enhance the value of a stone resource.

Tenax maintains a world-class laboratory in Verona, Italy where stone samples from quarries around the world are sent for analysis. Based on the stated objectives of the quarry or factory owner and noted challenges, either at the quarry or in the factory production, a very specific system of application and chemicals is developed. Once the system is implemented, the results yield enhanced value to the producers, and provide enhanced beauty in the stone for consumers, and ease of production to local stone fabricators.

Tenax is by far the largest supplier of epoxies and polyesters for the world stone industry with 75% market penetration, and estimates their closest competitor at less than twenty percent of Tenax’s sales volume. Mr. Borelli declined to offer sales figures.

Regarding my probing question, “Do resined slabs need to be sealed?” Domenico emphatically stated, “Absolutely.” Here is why.

Once a “system” is developed for a specific stone, the proper sequence of resining is as follows: slabs are cut on a gang saw or multi-wire saw, then honed to 120 grit.

The next step is critical, baking the honed slabs to a specific moisture content, cooled, and then resined. Once cured, the resined slabs are sent to the polishing machine for final grinding and polishing. This, of course, removes both applied resins and additional stone. Some of the resin is thus removed in the process, while much remains in the pores of the remaining stone.

More than 100 factories in Brazil do not hone the slabs prior to resining them. Many producers simply cut the slabs, dry them, then apply resin and send them through the polishing process.According to Mr. Borelli, “Resining granite slabs reduces the porosity rate by 30-35 percent.” What is, therefore, the implication? Granite slabs remain somewhat porous. But of course, it depends on the specific nature of the stone.

In my direct observations of more than 100 factories in Brazil, many of the small and medium-sized fabricators do not hone the slabs prior to resining them. Many producers simply cut the slabs, dry them, then apply resin and send them through the polishing process. This diminishes the intended results, although speeding up the process and achieving higher production rates.

Of course, the largest and most respected factories have highly automated processes that produce slabs in the correct sequence. The fact remains that much of the granite produced in Brazil skips the initial 120 grit honing step.

I decided to perform yet another of many sealing tests to validate the need for sealing. So, I used two samples, both 6˝x 6˝. One Crema Bordeaux, the other Santa Cecilia. Both of course from Brazil.

I masked off half of each sample and sealed half with HMK S34 Silicone Impregnator. The other half remained untouched from the factory. I drizzled a bit of olive oil and red wine (Trivento 2007 Golden Reserve Malbec) and let it sit overnight.

In past experiments (admittedly unscientific), I had found oils to be most problematic to granite. This time, I was quite surprised to find that the oil failed to penetrate both samples, although the wine did stain the unsealed Santa Cecilia sample (see images).

Of course, because there are literally hundreds of different granite colors from quarries around the world, there are no “One Size Fits It All” solutions when it comes to porosity of granites. Many granites never need sealing; some cannot be resined at all because they are not porous enough, while many lighter and medium colors are as porous as a sponge. Each stone type needs to be assessed based on its own specific characteristics.

For you, the busy fabricator-installer, the end result is it may be best to think of sealing granite as an insurance policy against many possible and unforeseen mishaps. Besides, many resourceful fabricators approach sealing granite as a profit center, selling maintenance products to current and former customers for many years after a successful installation.

Of course, the quartz producers may see this as a “weakness” of granite and push their manufactured product. There is little doubt, however, that the beauty of natural granite cannot be reproduced by anything engineered or man-made.

Finally, the statement made by the MIA about the lack of quality sealers before 1995 is not accurate. Since the 1970s I have used HMK S34 Impregnator in both residential and commercial applications without a single failure and it has been specified by thousands of Architects for decades.

Moeller-HMK practically invented the Stone Care industry. Since the 1970s, numerous quality penetrating sealers have been effective against household accidents common in kitchens worldwide. Products from Miracle, DuPont, Stone Care International, Akemi and Tenax have been providing peace of mind to homeowners, architects, designers and fabricator/installers, and will help prevent the dreaded “call back” by frustrated consumers.

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Torin Dixon is a 35 year stone industry veteran. Fabricator, Contractor, Importer, and Stone Care expert. For comments, he may be reached at or by calling 800-380-6881.