If your porcelain sink has some scratches or blemishes on it due to age and wear, there are a couple of things that you can try to remove them. One is to use specific solutions to clean and smoothen your porcelain. There are various products like these, such as Dial Corp’s Soft Scrub. Another way is to use very fine sandpaper to remove the scratches rather than cover them; 600 grit will probably suffice. However, when going this route, be very careful and do one area at a time so as not to damage the surface of your sink. Do it slowly and check to see if there is an improvement on the surface of the porcelain sink.