How To: Fix Dull Spots on Granite
I have had many recent phone calls from customers telling me that their granite countertops are getting dull, even after sealing. Any liquid can cause the dullness including water stains from a glass. Products like Windex and 409 are causing dullness, however cleaners meant for stone usage are not. I have granite tops all over my house that have been sealed, water, milk and other liquids gets on them everyday, and they are in perfect shape.
A couple of these people told me they bought these tops at big discount stores. Other people claim they bought from overseas suppliers that they picked up for a great price. Most of the calls I get are reported "absolute black" granite, but others have been on various light colored granites.
I am wondering if these tops were ever really polished or if they were just honed and then lacquered at the factory to make them shine. I remember 10 years ago we receive many phone calls about "absolute black" granite monuments. These monuments looked great when they were installed but after a rainstorm, they had streak marks that would not come out. I remember monument company owners telling me they had to pull the stones and polish them from 1000 grit diamond to final polish, using radial arm machines, to correct the problem.
Customers are asking me if they should fix it topical, (Waxes or lacquers), or if they should just polish the affected area. The problem with lacquers and waxes is that you are just covering up the fact that the stone is not really factory polished. As soon as some liquid settles on the stone again, the dullness will show, and you will have to wax it again. The problem with actually polishing the stone is that you will have to do the entire surface to make it look uniform and to prevent dull marks from occurring anywhere else on the surface. However, the cost, labor and complexity of polishing an entire countertop after it is installed, may make this the bad choice.
I decided to contact Chuck Muehlbauer, the Technical Director of the Marble Institute of America (MIA) to get his opinion. MIA members get to call Chuck free of charge, which I believe is worth the cost of membership alone, not to mention the other benefits of MIA. Chuck reiterated my story on the mystery of the black granite monuments of the past. He also said that he has had dull problems with a very limited number of overseas stones and stated, "I've had a few cases in condos where we did full scale investigations and petrographic work and discovered illite (a clay) lenses in the material. This made the stone not only sensitive to acids, but even standing water with enough dwell time would discolor the stone". Chuck's recommendation is "if you have one of these stones, I think your best bet is to candy-coat the stone with something topical and just live with it."
Hopefully, someone will figure out what is going on with some of these overseas granites. Until then, I recommend that you continue to buy your stone from a trusted distributor who knows his products. It just goes to show you that if something is cheap, there is usually a reason.
To obtain MIA membership, call them at: 440-250-9222.