Painting over plaster

Discussion in 'Painters' Talk' started by Dodge, Jan 23, 2009.

  1. Dodge

    Dodge New Member

    I have stipped of the wallpaper in my front room down to bare plaster. I wish to paint the plaster with Farroww & Ball paint. However there are a lot of hairline cracks on a couple of walls that need to be addressed. Should I use a fine polyfilly over the cracks, or should I dig out all the cracks first and then fill, sand and then paint. Any advice would be welcome.
    Thanks and regards.
     
  2. potty painter

    potty painter New Member

    Yes, open the hairline cracks a little before you apply the filler. Thing to remember here is to first remove the old paste residue from the walls, I would suggest sugar soap for this, you can apply it with a large brush 4" or above and wipe clean with rags. Always work from the bottom up, allow to dry and carry on with your application.
     
  3. Goodwill

    Goodwill Member

    Dodge,

    I would recommend that you wash these walls using clean warm water with no additives. Wet-in the walls with a broad wall brush, when sufficiently soaked, scrub with an old wall brush and scrape off all residues with your stripping knife. Wash down immediately and sponge-off using warm water from a separate bucket. Make sure you have done a thorough job.

    When dry, rub down with a pole sander using an abrasive such as aluminium oxide with a grit of between say 120 to 180. If the cracks are truly hairline I would not recommend cutting-out to make them wider. Fill with your fine plaster filler and rub down when fully dry, 240 grit is likely to be fine, keep the pressure light.

    Dust-off and size the walls with diluted fungicidal wallpaper paste as directed on the packet. I would recommend that you line these walls with a good quality lining paper of around 1000 grade rather than painting straight onto walls that have been previously papered. Use the same fungicidal paste as used for the size.

    You do not say what type of paint you are intending to use (water borne or oil medium), so I shall assume that it is an emulsion paint. Apply a mist coat, thin as advised on the can, followed by two full coats, depending on the colour and saturation.
     
  4. jcts

    jcts Active Member

    follow goodwill's advice because he's spot on. however, if the walls are ok after the prep you may not need to line so leave that section out and go straight to the mist coat
     
  5. Astramax

    Astramax Super Member

    All the fine cracks will eventually open up and make your hard prep work a waste of time, line as suggested by Goodwill the walls but use Wall Rock fibreliner a bit expensive but absolutely brilliant product.

    Not a lover of Farrow & Ball myself, Dulux do comparable colours for half the money.
     
  6. jcts

    jcts Active Member

    also with dulux, you'll only need half as much. F+B paint has very poor opacity IMO
     
  7. Goodwill

    Goodwill Member

    I wouldn't disagree with Astramax's comments regarding using a non-woven wall lining. Quick and easy, you may paste the wall and hang dry with no soaking time.

    You would do well to take note of the comments made by jcts and Astramax regarding your choice of paint manufacturer.
     
  8. potty painter

    potty painter New Member

    Dodge, it's your choice. I still say sugar soap there is no need to line the walls, and whilst I don't agree with your choice of paint Dulux is both expensive and overated, better option would be Leyland or Johnstones.
     
  9. jcts

    jcts Active Member

    dulux is expensive but it's a classic example of "you get what you pay for". i like leylands and think it's good value for money. however, i only rate a handful of johnstones products
     
  10. Goodwill

    Goodwill Member

    Potty,

    Why would you want to charge the plaster with sugar soap? It will be drawn into the plaster with no guarantee that it will be rinsed out again. At the very least, it would probably hamper the adhesion of the filler. Soap, in or on the surface, can never be a friend of paint.
     
  11. potty painter

    potty painter New Member

    What would be the comments on other far better over rated paints such as permoglaze, & sigma, what about woolworths, before they fell victim to these hard times their paint was of the highest quality. Little wonder when you consider it was made by McPhersons who were the paint suppliers to the leading health Authorities.
     
  12. potty painter

    potty painter New Member

    Hi there Goodwill. Truth is Whatever you choose to remove the old paste with, a certain amount will be absorbed by the plaster, Useing warm water will quickly activate the old paste with a lot of it being drawn in as would sugar soap. Both these methods will work but sugar soap will kill the vehicle of the paste, and become far less detrimental to the end result.
     
  13. ponty01.

    ponty01. New Member

    Because a non brand paint is made by a reputable company does not mean it is the same quality. Some manufacturers do this, because otherwise the product is found to be inferior and rejected by quality control, and would otherwise be rejected. Rebranding can actually create an income for an inferior, scrap product.

    PONTY: Plenty Of Names To Yawn (at) :^O
     
  14. potty painter

    potty painter New Member

    Ponty,

    Point taken, that can somtimes be the case. But as far as Woolworths and the Donald McPherson range is concerned a lab test conducted in 1973 confirmed that both contained the same chemical qualities.
     
  15. ponty01.

    ponty01. New Member

    1973 - not being funny but that was 36 years ago!!

    Would the same results be returned in 2009, and who would produce the stats? Independent research gives more reliable and trustworthy results than in-house research, or research by a chemist employed by the company, as they can have a conflict of interest.

    PONTY: Plenty Of Names To Yawn (at) :^O
     
  16. apl

    apl Member

    Hi there Potty, My local Johnstones has got special offers on at the moment on paint. I normally only use Dulux but tried the Johnstones covaplus. It went on well and covered in one coat (still give it two though, old habits die hard!) I've tried their professional white gloss but it seemed to drag. I'd use the emulsion again though.
     
  17. potty painter

    potty painter New Member

    Ponty,

    I can't with all honesty answer that one, But the tests i'm on about all those 36 years ago were conducted at Bridgend Tech college, for the all the Welsh health authorities. Sad thing is mate. I was there!!
     
  18. potty painter

    potty painter New Member

    Apl.

    youre right, johnstones gloss can tend to do that, Truth is there really is'nt a paint application on the market that really does what it says it will. I'm an old fashioned tradesman with old fashioned views, and all these one coat wonder paints of this modern age of ours are no different to what they were almost 40 years ago. Some work and some don't.
     
  19. Goodwill

    Goodwill Member

    Potty,

    Because these walls were previously papered, as well as the paste there is also likely to be size present. Putting aside the surface condition of the plaster, because of the likelihood of it not being possible to totally remove all of these contaminates by washing and scraping I recommended lining. The threat from the old paste and size comes from being left between the plaster and the new paint and affecting adhesion.

    The main constituent of sugar soap is washing soda, if any of the soap is left behind, which it will be, especially in the crevices of the hairline cracks, it is liable to attack the new paint and could lead to saponification, at the least tardiness in the drying. Remember, in straight forward terms, sugar soap is an alkaline soap preparation.

    I do not understand what you mean by "..... sugar soap will kill the vehicle of the paste, ......".
     
  20. potty painter

    potty painter New Member

    Goodwill, good afternoon to you.

    What I meant by killing the vehicle was the soda wil render the paste harmless, of course the walls will require scrubbing at least twice after the application of the sugar soap. I have used this method many times with good result, on saying that I in no way disagree with the method you suggested either. It is only the fact that I have never in the past had a problem with it that I thought it worth a mention.

    Potty.
     

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