A: Yes. Hope's Perfect Sink is great for removing water stains from black sinks, whether cast iron (porcelain enameled), or granite/quartz composite.
A: Thank you for your recent inquiry with The Home Depot regarding Hope's 8.5 oz. Perfect Sink Fresh and Clean Cleaner and Polish. Kohler only recommends to use the Kohler Neoroc Cleaner with this particular sind. We appreciate your business and look forward to serving you in the future.
A: Hi Moe, Container says: Uses: Great for almost every type of sink including brushed stainless steel, cast iron (porcelain), CORIAN (solid surface), composite, acrylic, and vitreous china. Do not use on mirror finishes and other finishes that specify a non-abrasive polish. Test before using.
A: Hope's Perfect Sink works great on black porcelain and may dramatically improve the appearance of your 25 year old sink, depending on the cause of the dullness. In any case, it is perfectly safe to try.
A: Depending on why your sink is dull - scratched, etc. Otherwise I'm sure it would do a nice job. Back of container says safe for porcelain. Maybe try a little corner first.