Difficult to tell, but it looks like those tiles are severely etched.  In which case I would say they are currently or did at some point use an acidic cleaner.

Lorne Greenberg
 
Fabra-Cleen
"Getting all the dirt since 1949"
lorne@fabracleen.com
www.fabracleen.com
212-777-4040, 718-776-3564
516-377-0993

On Feb 23, 2014 10:02 PM, "Roger Konarski" <qm144@yahoo.com> wrote:
Please see the attached picture. Is this a bad case of efflorescence ?

Thanks
Roger

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