Ken ..Now that I have been cut down to size for my political commentary and
chastised for my lack of "East Coast education" May I recomend one easy cure
for your side walk problem...actually two if you have to match the historic
orginal patena..If the patina is critical ..and it should not be as it is "a
sidewalk" i.e its patina changes daily ,monthly, and yearly...but if it is
critical may I suggest water glass treatments ( potassium silicate ) very
durable and the colors can be matched exactly with sample provided. and will
hold up with freeze thaw; and even high pressure water hose ... The correct
way; as any walking surface is intended ...is to resurface with a grit
suitable to the existing  patina.( perhaps 24 -80. then a diluted wash with
water glass....happy grinding you can call me for sources...but not
today..everything is closed  for our beloved George
Wallace....Oh..dear...there I go again...being touchy feely.....regards
Michael