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mist coat won’t stick to new plaster

Discussion in 'Decorating and Painting' started by John ruane, 15 Jun 2019.

  1. John ruane

    John ruane

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    This is my 2nd attempt at painting my recently skimmed bathroom and getting same results.

    First was a un-thinned primer which peeled right off, once dry, back to the plaster after i applied a bathroom paint.

    So scrapped the whole lot off.

    2nd attempt i did some research and bought dulux super matt which i thinned 50/50. First coat seemed solid once dry so applied a second coat but i can peel the whole lot off in strips.

    I should say i didnt let the paint fully cure cos wanted to test it - but should it do this? You can see from the picture that the plaster has got damp which i think is the reason it peels off.


    Spent hours painting and scrapping it all off, and looks like i’ll have to do again.
    The skim is months dry and was even sanded down before painting.
    Am i doing something wrong or will a mist coat peel when wet?
     

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  3. JohnD

    JohnD

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    Has anybody put glue on the plaster?
     
  4. John ruane

    John ruane

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    Is that a usual thing? The plasterer never said he did - can ask him. I know people who he’s don’t work for before and they’ve painted theirs without any mist coats, but not in a bathroom.
     
  5. Notadecor8ter

    Notadecor8ter

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    That looks very unusual like the paint is just not bonding.
     
  6. John ruane

    John ruane

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    How thin can a mist coat go? Should i try thinning it even more?
     
  7. JohnD

    JohnD

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    There are still a few people who put PVA on it.

    Not many.

    Most have been killed by angry decorators.

    Why is the wall wet?
     
  8. sparkwright

    sparkwright

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    The plaster somehow looks damp, and the loose paint looks very oblong, almost piece of tape shaped.
     
  9. John ruane

    John ruane

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    The wetness is from the second mist coat of paint soaking through i guess. I let it dry to the touch but not fully cure. Fully dry it wont peel as easily, but i know that when i apply a vinyl bathroom paint then that will give it the strength to peel off in chunks. Yes it comes off in long strips like wallpaper. Im using a scraper
     
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  11. Nige F

    Nige F

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    Try Zinsser Peel Stop .
     
  12. UncleB

    UncleB

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    you could try sanding the plaster to give the paint something to key into.
    I found one plasterer loved to give the walls a "like glass" finish which made it difficult to get paint to stick to until I did this - I used 240 grit paper to just break the surface a little all over.

    Whether this is an approved method I can't say, just the result of trial and error.
     
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  13. John ruane

    John ruane

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    I sanded the plaster, but it still felt smooth. After you apply a mist coat, if you wet it should you be able to scrap it off? It only comes off when either wet or after a second coat thats only just dried.
     
  14. JohnD

    JohnD

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    supermatt is a non-vinyl paint which is not durable. It is used on new plaster because it is porous and allows water vapour to pass through it to allow the new plaster to dry out. It is not suitable for wet conditions.
     
  15. John ruane

    John ruane

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    Yes im just using it as an undercoat. If i can peel it off when wet does that mean its not sunk into the plaster - or am i jumping the gun and when its dry then thats when it bonds? I dont wont to put a bathroom paint onto again if the base hasnt bonded correctly.
     
  16. SpecialK

    SpecialK

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    Did you wash the plastered wall to get rid of the sanding dust before painting? Maybe thin the paint down lots more and see if its stuck when dry...
     
  17. Yes, I have experienced the same, nice floating skills, thanks for making the decorating more difficult!
     
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