We have been having considerable trouble with efflorescence; straight scrubbing down with water does not seem to be of any great help. Can you suggest some form of acid wash?
A dilute solution of hydrochloric acid will be most effective; strength is best decided by trial on an inconspicuous section of the structure. It is essential that all surfaces be rinsed down thoroughly with clean water after the treatment. All traces of acid must be removed and if in doubt a test should be made with litmus paper.