Damp on side of chimney

[essex123456]

hi

I have a 1930 semi, I have opened up the chimney in the lounge this is against the party wall. It had been blocked up with a blocked vent, before we bought it. I have cleared the builders breakout the stack had dried out and we have had the room replastered, the room has dried out as it was about 5 weeks agar. but on the left hand side at the bottom, it still appears damp any idea what I can do? I think thi is damp rather than the plaster drying.

Ta

 

[^woody^]

Did you seal the wall to stop all the tar and flue gas salts leeching through, making the plaster hygroscopic and causing damp stains?

 

[essex123456]

No, but as it's on the side a the the very bottom I don't think that is the issue. And it's a small patch.