Flagstone Efflorescence

by Jerry
(Narbeth, PA)

in progress 6-10-2016

in progress 6-10-2016

in progress 6-10-2016

I had a new flagstone (Pennsylvania Cleft Bluestone) patio installed and within one week the flagstone developed stains and discoloration. I think it is efflorescence. What perplexes me is that the stains and discoloration (circles and framing?)seem to change almost daily. Furthermore,the patio I replaced (cement and mortar) was also flagstone, and I never had any kind of problem with it for the 30 years it was there. The new patio was laid on the cement foundation and a sand base. (See one of the progress photos below.) My contractor tried several washes, but no acid. Immediately after washing the stones look good, but then the next day all the stains are back.

Is there any remedy? Even if the patio is redone, how can I be sure it won't happen again?

Also, will those white "scratch" or "chisel" marks ever go away?

Thank you for your valued expertise.


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