painting new plaster

joeturbo · 30 Aug 2010

I have recently had 2 rooms plastered, and would now like to decorate. (I am not sure on the final colours but thought a base white would be ok for now)

I have purchased "Dulux Pure Brilliant white matt"

After reading a few posts I understand that I should apply a "mis-coat" (10%-50%). Reading on the side of the tub it says I should only dilute by 10% clean water or should use "Dulux plaster sealer"

Can anyone give me advice on how to get the best finish.

The finish of the plaster is pretty smooth but will probably still need to sand down imperfections?

TheDec · 30 Aug 2010

Joe.

You first need to allow your newly plastered walls to dry out before painting, this is very important.

Going to your choice of paints you have choosen a retail product as opposed to a Trade, but worry not it will serve you well. Perhaps within the trade one of the finest paints for misting is Dulux Trade Supermatt, and should only be thinned with approx 30% water.

A retail product does'nt have the consistency nor opacity of a trade quality coating, yet again! Worry not'

Your freshly plastered walls first need to be lightly abraded with around 80 grit paper, then you will need to apply your mist coat 10 to 15% water would be fine but no more should be added.

Your walls then will be ready to recieve the emulsion of your choice. One thing to bear in mind here is after prep your walls will require dusting off and a damp cloth would'nt go amiss on the skirts to remove any settled dust.

Good luck

Dec.

cocoots100 · 31 Aug 2010

New plaster should not be abraded, as this will scratch the surface and will be visible through the layers of paint. Apply a mist coat of thinned supermatt followed by two coats of whatever colour you are having on top in whatever finish.
After the misting, then the walls can be lightly abraded and any imperfections in the plaster dealt with (i.e. filling any holes, or scraping away any splashes of plaster).
Normally plaster is left to fully dry out for 6 weeks before any paint touches it, but recent technology has allowed products like supermatt to be used on plaster that is drying out (which is how you see these makeover programmes on the telly plaster and paint a wall in days!)

Reidjules · 1 Sep 2010

Hi all

I have a room where there's been some new plastering done, on one and bit walls, and the whole ceiling. The other walls have had the paper stripped, only to find a thin layer of polystyrene, which has also been scraped off.

I have been advised to use easy fill to make sure that all of the walls are nice and smooth. But should I apply the easy fill to the newly plastered walls as well as the scraped walls?
If yes, should I apply a mis-coat to the newly plastered walls before the easy fill or after?

And how long should I leave the laster to dry? It was done at least 3 weeks ago, and achieved an even very pale colour within a few days of being applied. To me it looks like it's dry, but I have read some advice that says it has to be left for 6 months!

Please help.

Richard C · 1 Sep 2010

New plaster should not be sanded unless the plasterer has made a pigs ear of it or it’s been over polished. Leave to dry out thoroughly for 10 days. For mist coats, I use cheap own brand matt white, thinned 25-30%, 3 coats in quick succession, dry overnight then your chosen finish. If you don’t thin the mist coats enough the paint wont stick. Don’t be tempted to use PVA.

Richard C · 1 Sep 2010

Reidjules said:
Hi all

I have a room where there's been some new plastering done, on one and bit walls, and the whole ceiling. The other walls have had the paper stripped, only to find a thin layer of polystyrene, which has also been scraped off.

I have been advised to use easy fill to make sure that all of the walls are nice and smooth. But should I apply the easy fill to the newly plastered walls as well as the scraped walls?
If yes, should I apply a mis-coat to the newly plastered walls before the easy fill or after?

And how long should I leave the laster to dry? It was done at least 3 weeks ago, and achieved an even very pale colour within a few days of being applied. To me it looks like it's dry, but I have read some advice that says it has to be left for 6 months!

Please help.

DIYnot Forum Rules
6) Do not hi-jack posts. Hi-jacking is adding your query to somebody else's thread.

joeturbo · 1 Sep 2010

cheers guys for all the replies.

Had just started sanding one small section then come online to check if i had any other replies to find now i shouldnt sand?? now im confussed lol.

So should i be ok to just use the paint I have "Dulux Pure Brilliant white matt" watered down by 10% for mist coat (1 coat), then sand any imperfections, then do 2/3 coats not watered down? I can then paint over that at a later date when i know what colours i want?

Cheers

Joe

TheDec · 1 Sep 2010

joe.

The sanding of skim does not scratch the surface, light abrasion flats back the areas and ensures good adhesion of your emulsion.

The paint you choose was a retail product and overthinning is not recomended, thats why the guidance they give you is 10% water and thats why I said no more than 15%.

Plaster skim can often be shiny in appearance "polished" it is just this type of surface that can reject your mistcoat and prevent the emulsion from adhering to the plaster. So in my opinion light sanding before application is a safeguard to avoid this occuring.

Dec.

TheDec · 1 Sep 2010

joe.

Sanding the skim does not scratch the surface, light abrasion flats back the plaster and gives a good key to ensure your mistcoat has good adhesion.

Plaster skim can often appear shiny in appearance "polished" it is just this type of surface that can prove problematic with regard to the adhesion of paint.

Your choosen product is a retail paint not a trade, and overthinning is not recommended, the advice stated on your product was 10% thats why I advised you not to thin any more than 15%.

Dec.

TheDec · 1 Sep 2010

Soory joe.

That was caused by losing internet connection.

Dec.

joeturbo · 1 Sep 2010

no probs, so just a quick light sand all over by hand using 80grit paper?

On new build properties would builders do the same thing?

Richard C · 1 Sep 2010

TheDec said:
The paint you choose was a retail product and overthinning is not recomended, thats why the guidance they give you is 10% water and thats why I said no more than 15%.

Raw plaster is extremely absorbent & you need the extra water to allow the paint to be sucked into the microscopic pores rather than just sit on the surface, you’re not looking to colour up the surface, merely provide a well keyed thin layer of paint. Thinning by just 10% is not enough & I always use cheapo own brand emulsion; applying 2/3 coats in quick succession will also ensure the plaster stays moist & does not suck the water from the paint before it has a chance to key. But don’t take my word for it, I’m just a plasterer

; check out what some other spreads think.

TheDec said:
Plaster skim can often be shiny in appearance "polished" it is just this type of surface that can reject your mistcoat and prevent the emulsion from adhering to the plaster. So in my opinion light sanding before application is a safeguard to avoid this occurring.

If the plaster has been over polished than I’d agree but if so, it’s either been done by a spread who really should be doing something else or because someone seriously ****ed him off & he wants to make the decorators life difficult. A normal, decent plaster job will not require sanding & mist coats in the way I suggested will ensure your paint sticks to the wall.

TheDec · 1 Sep 2010

joe.

Some will reckon that 80 grit is to fierce for this type of work, but I would tend to differ in my opinion. Useing 80 to 120 grit there is no need to apply any hand pressure simply allow the paper to only flirt over the surface.

The application of a mistcoat is the most important step regarding this aspect of decorating, and providing a key is of the utmost importance.

Yet my advice would differ if you were to use any other method other than Gods tools "your hands" In this trade they are often your best friend.

Dec.

TheDec · 1 Sep 2010

Richard C.

I take and understand your point, yet as said the mist coat is the most important first step to provide the adhesion of further coats, skim should be keyed if only as a guiding factor.

There is indeed far more important reasons why some paints should not be over thinned, take here for example a retail or trade product. Take also into account trade quality vinyl coatings that are dismissed by some as not ideal for misting.

Simple truth is they do have that capability, you are of course correct in what you say regarding skim being porus in the extreme, but as p&ds giving advice on a substrate of which we can't see an air of caution should be taken.

In this situation we talk of a retail paint as opposed to trade, these paints should not be over thnned, they dont have the opacity of their trade counter parts and more care should be taken with regard to their application.

Dec.

joeturbo · 2 Sep 2010

right, I am thinking of using the "Dulux plaster sealer" to be on the safe side. Im still not sure about when i should sand any imperfections? before or after the primer coat?

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painting new plaster

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