To Seal or Not to Seal?
If water does not bead on the surface and instead slowly absorbs and produces dark areas which a hair dryer will remove then your stone is not adequately sealed.
All untreated granites will absorb water and oils at different rates and are vulnerable to staining no matter how dense, this includes Black Galaxy, Ubatuba, Absolute Black and similar dark colored stones. The good news is that granite staining is not permanent and can be reversed. Even better still, granite sealing technologies are readily available which penetrate your stone to protect and prevent these problems from occurring in the first place. Your granite may have been factory epoxy-coated from the slab producer which will prevent sealers from penetrating. The finished edges and underside will still be susceptible to absorption and should be sealed. Sealers differ from manufacturer to manufacturer, as do their quality and molecular ability to sync with your granite's unique porosity. For best results a knowledgeable professional in your area should recommend the appropriate sealer for your particular stone and perform the initial sealing as well as successive sealing or instruct the homeowner in how-to applications.
Not all granites are granites. All hard igneous type stones are generally grouped with granites which should rightly contain adequately high percentages of quartz and certain minerals to be considered a true granite by definition. Special considerations are to be applied for stones outside of the granite family in terms of cleaning and preservation methods.
Vinegar, lemon juice; acids, as well as corrosive alkaline agents will not harm your non-coated granite. Granites are generally chemical resistant and even in extreme exposure can be easily restored to their original state. This is why granite is the first choice for monuments and commercial building exteriors.
Please note that some granite processors now coat their granite slabs with epoxy/urethane sealing technologies which may require special cleaning and maintenance considerations.
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