Dark marks after painting

danrv

UncleZen said:

WIAWSNB said:

What type of paint, Zen? It looks to have a sheen - is it 'silk'?
If so, why?
Silk is usually chosen for extra durability - washable and scrubbable - or to cope with moist areas like shower rooms, but is otherwise generally avoided 'cos it just doesn't look good. It also highlights any imperfections in the wall surface, and - lawdie - you shoor have some
And, as btw says, you don't PVA walls. This is very likely to 'reactivate' with the water in the paint and become soft again, and will often become tacky when rolled over, adding an unwanted texture.
However, if you applied Zinsser 123 over it all, then I'd have expected this to have sealed the PVA and made it even. Or did you just 123 the filled bits?
Anyhoo, the surface looks to be in poor condition to begin with - sorry.
I'd get a comfy sanding block, and some good quality aluminium oxide paper, say 120 grit. Work at it gently using large circular sweeps, without pressing too hard - give the surface a chance to powder away, without hopefully blocking the grit. You really need to get that wall looking smoother, and the filled parts as flat as the rest - and vice versa. I hope the PVA won't cause a sticky mess...
Once you actually get that wall flat and level, you may need to go finer - say 180 grit - for a bit, but hopefully not.
Wipe down thoroughly, and see what the finish is like. If acceptable, then roll on the Zin 123. Allow to dry fully, and then apply your paint - MATT.
Nice colour - what is it?

The paint is just for a colour test (valspar chain link), its mid sheen. Im using it as a reference to see if I want to buy darker or lighter, the end result will be matt.
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I do plan to sand this more to make it smoother as its not smooth enough for me yet. 

Thanks for your feedback, but they don't address my question about the dark area.

It hasn't helped by painting a large area with mid sheen for a test but hopefully the wall can be resurfaced. 
Maybe try a scraper and heatgun to remove the paint.
As it is, it'll take a fair bit of sanding to get that good enough for painting. 
Zinsser Gardz is used on plaster as a moisture barrier. I applied that in my bathroom once I mist coated the walls and ceiling. Probably isn't needed on that wall unless it's in a wet area.
No need for any priming until a skim coat is done.

The dark area is likely the paint absorbed into the filler as mentioned. Best to try and scrape the paint off and then key the wall with a bonding agent. 
Then look into a plaster skim. The roller idea shown looks good.

Lorian

Gardz would have been better and easier than bin.

That dark patch looks low to my eyes and may need a skim of filler.

The colour is pretty dark and the brush strokes do it no favours it's needs rolling for an even finish. If there are any imperfections Matt is more forgiving.

UncleZen

I did a 2nd coat onto the dark area just to see if it would look better, and it does.
The orange peely area is the existing emulsion finish that you typically get with a roller.
The area below is the old bare walls that once had tiles, and the horizontal lines are from the paintbrush applying the primer, and feel smoother in general because I've been at it with the 120 sandpaper (i.e. no orange peel) 

bjorn_toby_wilde

Gardz would be a good product to use as it should seal everything in, wallpaper paste, pva, etc and it will stop the filler flashing through. It’s a bit of a decorator’s problem solver. I’ve just used it to seal a mix of very old plaster, flaky paint and more recent filler before wallpapering.

One of the earlier replies mentions toupret fillers. Can’t recommend these highly enough. They’re a real game changer because they don’t flash and they’re really easy to sand. I like their boxed powder fillers as you can easily mix as much as you need and to the consistency you want.

Hope it all works well.

Lorian

Toupret ready mix code 812PP at Screwfix is my go to filler for this when saving time. Dries very quick even this time of year.

Once dry it's easy to sand then a thin roll of guardz and ready to emulsion an hour later.

 You can push the whole process in autumn/winter by running a good dehumidifier in the room. And painting with a good roller on a pole.