Q. I neglected to clean the black grout from white tiles quickly enough during installation. My new floor is stained, and the only remedy so far is to sit and hand scrub every single tile with Barkeep’s Friend and a plastic scrubber pad. After hours of this I was ready for the chiropractor and stopped. What can I do to remove the rest of it? Have I damaged the glaze on the tile beyond redemption?
— Cynthia Scott, by e-mail