difficulties with good emulsion finish on new plaster

[100mel]

I don't seem to be able to achieve a good emulsion finish on some walls recently plastered - coming out all patchy and uneven surface. I used thinned down emulsion on new plaster and then have given it 2 - 3 coats of thinned matt but still the finish is patchy

Any ideas as to what I need to do to achieve a decent finish?

I was pondering using Polycell basecoat first and then going over with another coat of matt

Hope someone can advise

 

[Richard C]

Could be the plaster has been over polished, the plaster has been sanded exposing the grain or the spread has somehow got PVA on the plaster surface. How recently was it plastered? Are you using roller or brush? The finish will only even be as good as the plaster finish, if that's rubbish the paint finish will also look rubbish!

Might pay to let it dry out thoroughly for a couple of days & test if the paint is sticking to the plaster, if it is try again.

 

[100mel]

It was plastered about 6 weeks ago - no problem with paint adhering but in areas it is as if the paint has just sunk in leaving rough surface - I would say reading your reply that it seems as if grain is exposed and surface therefore seems rough

Should I rub down with glass paper and repaint maybe with basecoat first before recoating with emulsion or maybe an oil based eggshell on first?

 

[Richard C]

It’s difficult to imagine how bad it is from your description or if you’re just expecting too much; no offense intended but some folks seem to expect a car showroom finish which is both unrealistic & impractical but you should not be able to both see & feel roughness but you will never eliminate light brush marks or the mottling effect of using rollers.

Base coat is a DIY product aimed at covering all sorts of imperfections, sins & outright bodges which will leave the walls looking awful IMO. Personally I wouldn’t touch the stuff & if the finish is sufficiently bad to warrant it's use, I would be calling back whoever did the plastering to sort out it if I could; who did plaster the walls? As I said previously, if the finish on the plaster is rubbish, virtually no amount of paint is going to cover it up; you could try lightly sanding back when the paint is thoroughly dry or even locally filling the rough bits, sanding back & re-misting but if we’re talking large areas, frankly, it’s quicker & more effective to re-skim the entire wall to the standard it should have been done in the first place.

 

[100mel]

Getting the plasterer back - not an option - bloke has disappeared/gone out of business - agree that it is probably a plastering problem

Accept what you say re basecoat - shall I use a fine grade of glass paper and then reemulsion - brush might actually be better

Brush marks/roller marks etc not the problem as long as it achieves a uniform finish!

 

[Richard C]

I use P120 grit, wet or dry; more expensive than sandpaper but much better IMO & it lasts a lot longer. P120 can be a little coarse at first so don’t go too mad with it until it dulls & clogs up a little; or go for P150 grade; sand in straight lines, not circular.

I always use a 5 inch brush on new plaster as (for me) I can get a much better finish with slightly thinned emulsion (10%) but, in your case, I would advise a mohair (synthetic) roller. Again, slightly thinned emulsion; the roller will give a very slightly mottled finish, something I don't normally like but it will help hide the texture differences you will get between the filled & sanded bits over the already painted bits.

 

[100mel]

Many thanks - I will do this - hadn't tried wet and dry at all to date

 

[Richard C]

Many thanks - I will do this - hadn't tried wet and dry at all to date

Use it dry though, not wet