In November, we had a contractor build an outdoor fireplace that was finished smooth stucco. The structure walls were Hardie cement board. I'm not sure what other layers/coats of materials were used under the stucco.
When it was first completed, the stucco looked great; but after the recent rains we had here in Southern California, the entire finish is now covered with a while splotchy film (photos below.)
The contractor told me that this is efflorescence. I've seen photos and real-life examples of efflorescence, and while problem looks similar this seems to be much worse than any example I've seen. The white film covers the entire structure.
We have another structure, built by another mason, finished with the same stucco, that is not exhibiting any of these problems.
I suspect the the contractor did something incorrect in the finish. I understand that efflorescence is normal, but whatever this is, it looks really bad.
I've read up on suggestions for cleaning, but haven't tried anything yet except vinegar, which did nothing. I'm not looking forward to scrubbing the whole thing with a stronger acid, but it seems to be the only alternative.