Dark Rings On Ubatuba Granite Countertops
How do I remove dark water-rings on Ubatuba?
Huh... don't know that I can answer that one without more info.
Most Ubatuba granite is dense and not very porous. Meaning it does not stain easy at all. Also, it does not etch.
"Water-rings" are an etching issue with marble. The only answer that makes sense
is that a sealer was applied when it probably didn't need to be. The sealer didn't absorb well as you'd expect with Ubatuba and dried on top or at least left a residue on the surface.
Now some sealers are sensitive to acids. Meaning the sealer itself (not the stone) will etch and show water-rings, etc.
It is also possible that your slab was resined at the factory before polishing to fill small pits or voids... perfectly normal, but sometimes you see etching with resined slabs.
The only problem with this answer is that etch marks are usually "lighter" in color. You say the rings are darker, which usually happens with staining. Here's what to do:
1.Buy methylene chloride (powerful solvent-use carefully)
2. Pour some MC on a small area with rings.
3. Let sit-scrub with soft brush-let sit and wipe clean
Did it remove the ring?
If yes, squeeze a puddle of lemon juice on the cleaned area... let it sit a few minutes and wipe.
Did it leave a mark? If no, then you have removed whatever was on the surface and getting etched.
If it does leave a mark, then try cleaning with the MC again, but if the lemon juice keeps leaving a mark, then I don't know what is happening.
If the methylene chloride does not remove the original water-ring then you have a stain. Rare with ubatuba, but still possible.
If you have a stain, then you'll need to follow the instructions in the Removing Stains guide.
Stains are removable, but the procedure depends on what stained the granite... it's all in the guide.