I decided to skim one wall of my bedroom which had some new wall lights and sockets moved around. I PVA'd and bonded the chased walls first then applied PVA to the entire wall and skim coated it with Thistle Multi finish once the PVA was tacky. I have attached before and after pictures (don't mind the skirting board). I have kept the window open for the full 2 weeks and it seems like half my wall is still of a darker colour. Is this normal? Is there any other way to test if the plaster is dry other than looking at the colour? Any help would be really appreciated.