I have recently had some walls & ceilings plasterboarded and skimmed, i left them for a month, when i came back i noticed some dark circles had appeared on the plaster about the size of a football, when i painted over them with 2 mist coats and a topcoat, they still came through the paint, does anybody know what these are and how they are caused?
P.S they are all on the walls but not on the ceilings.
Thanks
P.S they are all on the walls but not on the ceilings.
Thanks