Q. I have a spot on my granite countertop that looks like the finish has been removed. I had overripe tangerines sitting there, and I think the juice ate away the smooth finish. You can see the outline of the mesh bag they were in, and the small area is rough to the touch. I have tried cleaning off the surface and using polish. Once the area dries, the rough patch comes back. Is there anything I can do to restore the surface? Thanks for your help.
TIM HALL, Plymouth
A. I reached out to my friend Ted McFadden, author of the book “Stone Care Guide,’’ for advice. Ted said there was an acid reaction between the citrus and calcium carbonate that makes up the surface of the counter — one that is probably not true granite, but a composite. Granite is made up of quartz and feldspar and many other minerals. Granite is an ideal countertop material for kitchens, because it is not reactive to acids. This is more common to calcite-based stone such as marble, travertine, and limestone.
It must be understood, though, that some slabs sold as granite are actually composites, with calcite and other reactive minerals. It is important when selecting granite for a counter that you test it to ensure it will not etch. Use a little bit of lemon juice in the corner and see whether it reacts and removes the shine after a few minutes. Better to have the etch happen in the slab yard than in your kitchen.
The solution to your problem is to have the counter professionally refinished and polished. A professional evaluation will also tell you exactly what kind of stone you are dealing with and provide you with the information you need to keep your counters looking good for the longest period of time.
Q. The granite counter in my kitchen is changing color around the sink and on the lip above the dishwasher. I assume it is from water around the sink and steam from the dishwasher. How can I prevent further discoloration? Is there any way to return the discoloration to the original color?
LINDA CIGNETTI
A. I bet you’re right; the counter is probably absorbing water. I reached out to Ted again for advice. You must regularly maintain granite surfaces that are exposed to constant moisture by removing residues and sealing with a high quality product.
If the surface is not darkening everywhere, then sealing the affected areas exposed to water and steam should help reduce or prevent continued absorption and discoloration. The surface is dark because it has absorbed water. If the areas are sealed properly, the surface should dry over time. If your sink is an under mount, you must check the caulking around it regularly to make sure moisture is not getting under the counter.
Rob Robillard is a general contractor, carpenter, editor of AConcordCarpenter.com, and principal of a carpentry and renovation business. Send your questions to homerepair@globe.com or tweet them to @globeaddress or @robertrobillard.
