My bathroom sink consists of the same material as my tub. I assume it's some type of ceramic? I really don't know. However, my sink has dimmed somehow. Not sure. I don't use harsh chemicals on it. My bathtub is still shining, but my sink has turned lackluster. What can fix this?
Spray a Tub/Bath/Tile Spray on it and rub good. Should work.
I use the S.C. Johnson product called Scrubbing Bubbles, which removes dulling material and gives the sink a nice shine. Click on the below link for information.
I agree with Jolly, Scrubbing Bubbles works wonders on my bathroom sink and has brought it back to a shine that I never thought I'd see on it again! They have a maximum strength formula now that is great. Just spray it on, let it sit for 1-2 minutes, and wipe off. You won't believe how wonderful it works ... and smells.