Water Marks on Angola Gold Black

QUESTION:

We had Angola gold black granite put in our kitchen about 6 months ago. We noticed water marks which appear to come from the bottom of glasses in several places. We thought maybe we need to seal the granite, though we thought it was sealed before it was installed. I read about "doctored" black granite. Do you think this might be the case here? Also, I read that some black granites don't take kindly to sealing- leaving white residue. Would that happen with Angola Gold Black? Thanks for your help.

ANSWER:

In general there are many stones that are known to be either very dense and don't need sealing or very porous and shouldn't be installed in the kitchen.

But as a point of education, the only way to tell for sure is to Test the stone or a sample. Spill a puddle of water on the surface and let it stand for a few minutes. If the surface darkens under the water, then the stone is absorbent and should be sealed. If it goes 15-20 minutes or more with no color change, the no sealer is needed.

Based on what you've told me... yes, the Angola Gold Black has either been doctored or a sealer was applied when unnecessary. Most likely the rings are not caused by water, but by acidic drinks (soda, juice, alcohol, coffee) that are reacting with the sealer that is just sitting on the surface (when it should be below the surface in the pores) or the "paint" used to doctor the stone. It's a bit odd that it's taken 6 months to notice problems, unless you just finally decided to investigate.

Either way you'll need to strip away whatever is on the surface probably with methylene chloride, which is really toxic. I recommend hiring someone to do it.

Once stripped of any sealer or doctoring substance you can test your stone to see if it needs sealing.

It is possible that it needs sealing, but it was improperly applied the first time leaving the residue on the surface, which can happen with nearly any stone if you let the sealer dry before removing the excess from the surface.

Sorry to hear about the trouble. Hope this helps and good luck.

Ryan