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To Seal or Not To Seal

Sealant Test

To seal or not to seal. That is the question. Or rather, it’s one of the several questions we get here at Zimmer Marble regarding the intrinsic differences between stone options.

As you may know, granite, marble, soapstone, and quartzite are known as “natural stone.” They fall into that large category of gorgeous elements blasted from the earth and polished into luxurious style that retain the inherent durability of a material that’s been sitting under tons of rock and soil for millennia. Quartz, on the other hand, is what is known as “engineered stone”—a surface fabricated from rigidly strong quartz particulate and high functioning resins through a process of extreme heat and pressure. This process is so intense, in fact, that the resultant quartz countertop surface is functionally non-porous. By contrast, the nature of granite and marble is such that microscopic pores are ubiquitous across the surface. Though invisible to the naked eye, these pores leave the stone susceptible to staining when exposed to extreme elements, like fiery chili sauce and $5 boxed wine.

Because, of course, in moments of weakness even the most sophisticated palate will crave such aberrations from high cuisine, the stone industry has developed some sealants which effectively cover the pores of natural stone, making it highly resistant to stains and discoloration.

These sealants are relatively new products, having hit the market only in the last 20 years or so. Prior to that time, the peoples of Greece, Rome, Egypt, Italy, and the far eastern kingdoms all used natural stone (without the sealants) and suffered no ill effects. Think here of stone hearths with pots of bubbling stew, mortar and pestle systems grinding exotic spices, baking stones with sizzling flat bread pizzas, and dough-rolling areas with floury raisins spilling out onto the marble. Now that your mouth is watering, remember that for the entire history of human existence (with the exception of the last 20 years), no sealants were even available for these natural stone food preparation areas, and remarkably the species did manage to survive.

Before a natural stone job leaves our fabrication facility here at ZM, an industrial grade sealant is applied which will protect the stone for several years under normal conditions. Over time, especially in high traffic areas, the sealant will naturally wear off. We usually see the first signs of this on the corners of raised bars where people tend to lean, around the sink and where dishes sit to dry, and the main food preparation area. In second homes and residences where neither party has any interest in advancing their culinary prowess beyond the occasional PB and J, the process can take decades. In kitchens that are used twice a day for a large meal, it can happen in as little as a couple of years. The inherent porosity of the stone itself can also affect the timeline: marble is a naturally more porous material than granite to begin with.

So: do you have to reseal, and if so how will you know when it’s time?

First: you don’t have to reseal your granite. Yes, without the sealant, it will be more susceptible to staining, but many people appreciate the patina the stone acquires as it grows with your home. Just as you expect your cabinets to age, you can expect an unsealed natural stone to develop more fully the longer it remains in your home. If you choose not to reseal, you are not out to lunch (well, actually, you may be) but you are accepting the risk (read: certainty) that the stone will absorb the flavors of your life.

If, by contrast, you are looking for a more unchanging beauty in your stone and are interested in having it resealed periodically, you will of course wish to know when it is required. The simple test is as follows: pour some water onto the high-use area of your stone and leave it for 10 minutes or so. If, when you return, the water is still beaded up on top of the stone and upon wiping it away you see no discoloration in the surface, your sealant is still intact. If the water has apparently been absorbed into the stone, so too will other substances be absorbed and it may be time to reseal. Remember: the purpose of the sealant is to reduce the porosity of the stone, so that’s what you’re checking for with this test. So you’ve decided to re-seal the granite, you’ve done the test and found that It Is Time (said in the voice of Rafiki encouraging Simba to take back Pride in his Rock or something like that), and now you want to know how to do it.

For the handy person who is competent to read all the way through the labels on the back side of chemical bottles, a water-based sealant is available online or at the hardware store. Alternatively, you can place a service call to us here at ZM and one of our professionals will come out and strip away all vestiges of the old sealant and apply two coats of an industrial-grade oil based sealant which will last longer and better protect your stone than the alternatives available to the layman. Not that I’m trying to sway you either way.


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