On Sun, 25 Aug 2013 10:24:09 -0400, micky
wrote:


http://www.contractortalk.com/f48/oi...gstone-101167/
no great answer today, but these guys are really contractors for the
most part, and their talk is interesting.

In the last comment on the page, the poster said "...tried brake
cleaner, carb cleaner, and wd40. Not much effect on the stains."

Sulfamic acid is mild and used for tile and grout cleaner, can't say
if it will work as I've not tried it flagstone.