Almost every commercially available "Black Granite" sink is not granite. They are synthesized from stone sand and plastic resin technologies. Contrary to widespread belief they will stain, they do fade, they do scratch, and are susceptible to heat damage. Fiberglass, plastics, and marine industry suppliers carry more specialized cleaning products for surfaces containing resins. You may use any of the following for difficult stains: Acetate, Lacquer Thinner, Rubbing Alcohol, Ammonia, Mineral Spirits, Vinegar, Formula 409, Paint Thinner. Try to first identify the stain type and then match with the appropriate chemical product for efficient removal. examples: water base, oil base, protein base, coffee and tea, juice and dye, organic, inorganic hard mineral deposits.
Safety First: As with any chemical product exercise caution and read instructions thoroughly before use, properly handle and store the chemicals safely after use and be sure to neutralize then clean-up chemical residue afterward with milder detergents intended for food-safe zones. ie: dish detergent.
Caution: When using pads, scrubs, or brushes, be careful and use light-fine abrasiveness since medium-coarse will dull the finish of engineered, man-made stone. Some cleaning products may contain abrasives which in combination with your scrubbing action may dull the surface. Wipe or squeegee the surface periodically during this process and monitor your progress to avoid further damage.
The Preferred Method: Usually a hot water pre-wash, a mild de-greasing detergent or cleaning vinegar and some scrubbing action, followed with a hot-water rinse will remove most stains.
Real Stone: Granites are not considered sensitive stones and are unlike marbles, limestones, travertines which require special consideration. Granite cleans up easily with strong de-greasers. Acids will not damage granite and will remove what de-greasers won't as well as restore lustre. Cleaning Vinegar +10%, citric acid, oxalic, sulfamic, phosphoric, muriats, etc. A medium to coarse scrub brush will help facilitate the cleaning process. Always rinse well after any cleaning process. Seal your newly cleaned and completely dry granite with a top quality sealer so that water will bead on surface. This will help to prohibit staining formation. Liquid spray waxes buffed onto surface add an extra skin of protection and should be part of a regular cleaning program; Zep, Gel-gloss etc. These products can be added to without stripping off previous coatings. Silicone penetrating sealers and acrylic wax topcoats work better than older methods like mineral oils for example. Enjoy your stone! firstname.lastname@example.org