That is efflorescence that is coming up from within the stone and the calcereous salt deposits are being trapped by the topcoat as the moisture evaporates. Need to remove topcoat and seal with something that impregnates the stone.  Aldon makes products that work well. Dry treat Intensifia is really great and doesn't stink as much but much more expensive.

________________________________________
From the desk of
Baird Standish
Managing Partner
Facility Specialists, LLC
15 West Highland Ave. Suite E
Philadelphia, PA 19118
Phone: 215-732-7505
Fax: 215-546-9160
www.facspecs.com

> On Mar 24, 2017, at 8:31 AM, Mike Alston <realmikealston@gmail.com> wrote:
>
> Good morning, customer has a Slate porch that they sealed themselves and everything has turned white. They had someone come out with an unknown cleaner clean it. They themselves tried cleaning with vinegar and salt, now salt stains have covered most of the porch. Any ideas on how this can be repaired.
>
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