We have tried EVERYTHING to bring it back to the nice marble white top. Tried everything on-line searching for an answer and there are plenty…and none of them worked. Called the manufacture and they said, you cannot bring it back to white again. Lowes had some ideas, but they didn’t work either. The only thing we did not try and you may want to try was high strength peroxide. Not the stuff you buy at the drug store, you need 40 to 60% peroxide instead of the 3% you can buy anywhere. Where do you get it? At a beauty shop supply store like Sally’s. You put it on a cloth and leave it on. Do a search on peroxide cleaner or something similar. Good luck. In case you are curious, how did we solve the discoloration problem? You can have a service that comes to your house and applies epoxy your sink. Not cheap, but cheaper than a new sink.