I just removed some added on stones from an old tile fireplace hearth. The
mortor which was on the tile just lifted off, and scrubbing removed most of the
remaining mortor. There is a remaining film of mortor which apears to have
gotten into pores of the tile, and I would like to figure out a good way to
remove it. This appears to be just mortor 'powder' which got into pores during
the cleaning process. Can anyone suggest anything that would help remove this
residue?

Bob F