To Seal Or Not To Seal? (August 2007)

  It never fails; whether I’m fielding inquries on the radio, in my office or from the podium at a trade-show seminar, I get the same one over and over and over. And it can be asked again – right after I answer it – with only a slight change in wording.
  “How often should we seal?” “Does granite need to be sealed every six months?” “How many coats (that is a sore point with me) does it take?” “Should we be recommending that all stone be sealed?” “How many sealer applications are needed on every installation?”
  And it goes on and on, with some seminars becoming a long merry-go-round of these questions. Is anyone taking notes?
  First of all, when speaking of sealers and stones, it’s not coats as in coating. It’s applications, as with an impregnating sealer that impregnates (to fill throughout or saturate) or enters into the stone.
  Second, stone is natural. One piece of rock isn’t like the other. This is one quality that actually makes this stuff so beautiful and in demand; it’s individuality.
  This also means that no two slabs have the same absorbent qualities. If all stone came from one quarry, it would be similar, but still unique. Black granite from Africa may not absorb anything, whereas similar black granite from Asia may be a sponge.
  What does that tell us? Not all stone will take a sealer. If a stone cannot absorb anything, an impregnating (one that absorbs into the stone) sealer won’t sink in, either. The good news here is that if a sealer won’t penetrate into the stone, neither will a stain.
  This may come as a surprise to many in the countertop industry. Go to any home show and ask countertop people that sell anything other than stone what makes their product better than stone, and you’ll get the same answer. They’ll all say that stone needs to be sealed every six months, and their (fill in the blank) surface doesn’t.
  Now I have stone in my house that has never been sealed. Have I done something wrong? No; I’m doing something right.
  The need for sealing every stone, and sealing it often, is a myth, an urban legend. These kind of tales are born of fears and insecurities, or specifically designed to prey on such concerns. Everyone loves stone, but there is a certain mystique attached to it that scares anyone who knows little about it. It’s almost as if they’re afraid to do anything with it because if it’s ruined, it’s too too expensive to replace.
  If this is the only perceived weakness of stone for many, it’s easy to spread the urban legend that “all stone needs to be sealed.”  It makes sense to them and is a compelling reason for you to buy their product instead.
  A sad consequence to this, though, is when people in the stone industry start to believe it and spread the misconception. Let’s just take a look at sealing and the ifs, whens and hows as it relates to stone.
  In my opinion – and remember, I do stone maintenance and restoration for a living – perhaps only 10 percent to 20 percent of the commercially available polished stone used for countertops needs a sealer. Therefore, if only 10 percent to 20 percent of polished commercial stone countertops need to be sealed, then (and I know I’m Canadian, but this is not metric math just simple math) that would mean that 80-90 percent don’t need to be sealed at all.
  Only 10 percent to 20 percent of stone sold for countertops needs to be sealed because granite is the main stone variety in use, and only a handful of granites are absorbent. You can see this on something as simple as a granite boulder in a park or field; after it rains, it doesn’t stay wet. It dries instantly.
  Homeowners and fabricators can make the same test. Leave water on a slab for 10-15 minutes and then remove it; if water doesn’t darken the stone when it’s removed, the stone won’t absorb water-based staining material. If you’re shaping an edge on a granite top by working wet, and the stone doesn’t stay dark when the water is removed, it won’t absorb a water-based sealer, either.
  You can use a solvent test to see if a solvent- or petroleum-based stain will enter the stone. Simply dab some mineral spirits on the slab and leave for 5-10 minutes. If, after you remove it, it doesn’t darken the stone, neither will a staining agent.
  If it does go dark, no worries about damaging the stone with the test; the mineral spirits will completely evaporate, leaving the stone its natural color. But, this will tell you that you can use a solvent-based sealer to protect against oil-based stains.
  In short, if the stone goes dark with either water or mineral spirits, then seal. If there is no color change after testing with these two liquids, you don’t – in my opinion, need a sealer.
  This test works for granite and almost all other stone, although there’s a caveat here for marble; an impregnating sealer will not protect marble against those nasty water rings and spots.
  They aren’t stains, no matter how bad a customer wants them to be stains; they’re etches or corrosion. It’s a chemical reaction between the calcium in the stone and the acid in the product that caused the etch.
  Think of your favourite shirt in the laundry. When you spill water or oil on it, it goes dark. If it stays dark, it’s a stain. If it loses its color, it is bleached out or white, as the dye or colour from the thread is gone.
  On marble, the surface of the stone is corroded, leaving the stone in its real natural state or, for lack of a better explanation, its unfinished look. No amount of sealer will bring the color back to an etch; it needs to be resurfaced.
  It’s also important to emphasize that I’m talking about commercially available polished stone. When stone is polished, the pores are tighter and restrict the ability of liquids to enter. With honed surfaces, liquids can enter some of the less-absorbent stone more freely and therefore require an impregnating sealer – but still not all.
  One of the usual questions to pop up is, once you determine if you’re going to seal stone,  how often to do it.
  This answer is the easiest:  When your countertop no longer repels water or oil. The field test is that, after washing the dishes, a customer starts to notice the stone is darker with moisture and then getting lighter a short time afterwards, it’s time to re-apply (not coat) with the brand of sealer used originally.
  This is going to vary time-wise from stone to stone because – remember – no two stones are alike. But, any sealer worth its weight in gold (and the good ones aren’t cheap) should last you from 5-15 years, even with the most-porous of stones.
  Let me qualify that last statement. Any solvent-based sealer should last that long or even longer. I know that nano water-based technology has come a long way, but I have yet to find a water-based sealer that holds up as good as a solvent one. Now, this is my opinion only (but shared by many people I’ve talked to about it).
  I’ve discussed this with many manufacturers; some agree that water-based sealers are a long way off from the protection offered by solvent-based ones, while others maintain that their water-based solutions are better. I can’t test them all, so I’ll stick with my thoughts on this one until I can be proven wrong (and not by some manufacturer-oriented spin-doctor-type stuff, but some real independent testing).
  Get ready though, for more water-based products, because certain areas are starting to ban the use of solvents. California is one place in particular, and it also happens to be the home of several impregnating-sealer manufacturers.
  Another reason is that when you make a really good product that isn’t needed very often; you tend not to get many immediate repeat customers. With the increase in competition as well, customers are confused and sales grow stagnant. If the government is in the mood to outlaw what works, why not create a product that does need repeat customers more often with a safe base?
  I understand the reasoning behind this, and I don’t think the companies are wrong for thinking environment-friendly. Many are trying to create newer, safer formulas that last as long as the solvent-based ones, but we could be years from that.
  So, as far as lifting the mystery of sealing stone: Seal when needed, and try to use products that don’t require frequent repeat applications. Don’t fall prey to the urban legends and most importantly…….keep your stick on the ice.
  Tom McNall is founder and owner of Great Northern Stone Care, a Huron Park, Ontario-based stone-cleaning and -restoration company servicing all of southern Ontario. Tom also offers corporate and private consultation, serves as a trainer for the MIA, and is also on the organization’s board of directors. He can be reached at tom@greatnorthernstone.com