Have a bit of a problem and wonder if anyone has come across the same thing on a small slab repointing job.
On a natural stone slab we have cleaned of dried cement mortar left from earlier pointing with Wicks brick acid. We have then repointed with portland cement and building sand applied as a semi-dry mix.
Left the job thinking all was well.....5 days later customers let me know that brown stains had appeared on 5 or 6 of the slabs.
Have tried to remove stain with brick acid (which I appreciate might have been the original culprit). Although a slight improvement the stains are still there.
Any ideas anyone??
On a natural stone slab we have cleaned of dried cement mortar left from earlier pointing with Wicks brick acid. We have then repointed with portland cement and building sand applied as a semi-dry mix.
Left the job thinking all was well.....5 days later customers let me know that brown stains had appeared on 5 or 6 of the slabs.
Have tried to remove stain with brick acid (which I appreciate might have been the original culprit). Although a slight improvement the stains are still there.
Any ideas anyone??