On Thu, 10 Jan 2013 14:37:51 -0500, "Percival P. Cassidy"
wrote:

Our porcelain-enamel kitchen sink has developed stains, especially where
the plastic "feet" of a "sink protector" have rested. I think that stuff
that has been dropped into the sink and not rinsed away immediately has
caught on those "feet" and remained there long enough to stain the
surface. I have cleaned the sink from time to time with Soft-Scrub, but
hat no longer seems effective, and now I find that the stained areas
actually feel rougher than the unstained areas.

Any suggestions how to fix this problem? Any way to seal the surface?

Perce

Not sure the best way to clean stains, but the sink can be refinished
easily by a pro. No need to remove the sink. It takes maybe an hour
and not usable for a number of hours until cured.

I've had sinks done a few times - at home and at rental properties I
had. If the enamel is really worn a resurface would better, Imo.

You might check a sink resurfacing web site for cleaning methods.