paste on bare plaster

[jessie m]

hi all
ive stripped some paper off a ceiling which is now showing bare plaster. my question is,does the ceiling need washing to remove old paste or will a primer do the job.......thanx......

 

[misterhelpful]

If you are just going to paint the ceiling you should ideally wash the surface with sugar soap solution and rinse. When dry, apply a mist coat of emulsion watered down with 15-20% water to re- seal the plaster and allow to dry thoroughly before applying the finish coat/s.

The alternative is something like Zinsser Gardz http://zinsseruk.com/shop/Product.aspx?cId=130&pgId=359 which seals the paste residue prior to painting, but the first method is used most - and the cheaper!

 

[TheDec]

It is not a good idea to charge bare plaster skim with sugar soap, doing so can be very problematic.

Remove the paste useing warm water and a broad edged scraper you will find that it will take more than one attempt, then you should be fine to apply your mist coat.

Dec

 

[misterhelpful]

It is not a good idea to charge bare plaster skim with sugar soap, doing so can be very problematic.

You're right - my mind was thinking soapy water but my fingers were typing something else.


However, I wouldn't say it can be very problematic , provided it is rinsed well.

 

[TheDec]

If it was applied over a painted surface a quick rinse would suffice, yet plaster skim will absorb most if not all of the formulation. Hence this will leave a very unstable surface for any future paint sytem.

Dec

 

[Robbie uk]

There is a possibility that even after washing the paint may react with any paste residue that has not been taken off. A thin coat of oil based undercoat to seal the ceiling may be better before any emulsion is applied.