I'm removing a failed mist coat back to bare plaster and I want to buy a primer to seal the plaster as I've read so many people are having problems with paint peeling/cracking for whatever reason so I thought about buying a plaster sealer but which one should I buy so I can use dulux retail matt.
ASK painter & decorator.
I've never painted skimmed walls before but since removing the mist coat I can see a few problems that might have caused the mist coat to crack and not adhere to the plaster.
1, When doing the mist coat you could see stains in the plaster in places (Maybe pva mixed in plaster).
2, Plaster is so thin so maybe pva is reacting when mist coat soaked in.
3, One wall looks shiny and after sanding with 120 grit the wall still feels very smooth and the pours of the plaster looks very closed.
Plastermatic.
I've read people that have used a 50/50 ratio or 70/30 and have had problems with paint peeling or flaked. What emulsion would you recommend as some say use a vinyl matt and some say a retail matt but most retail matt is wipeable.
Are you a tradesperson and able to answer this question?
Hi Matt.
This is advice is given on the basis that you have mamaged to get back to bare plaster.
I wouldn't bother with any commercial plaster sealer tbh. Just a simple mist coat followed by 2 coat neat coats of emulsion would do the job.
The reason paint usually peels away from plaster is for a couple of main reasons
1- The plasterer who plastered the ceiling over polished the plaster closing the surface off. Affectively only allowing the water innto the and stopping the paint from soaking in to the plaster.
2- The mist coat was too neat meaning what little water there was is absorbed leaving the vinyl element of the paint on the surface of the plaster instead of actually soaking into the plaster evenly.
So my advice would be to sand the surface only with a quick rub to open the surface back up, with a p180 grade sand paper. Dust down the surface with a brush to remove any excess dust.
Mix a 50/50 ratio of water and emulsion (white wash). Paint the whole ceiling making sure to coat everything and not to go too mad on this coat. You still have two more coats to go on there.
Just make sure everything gets a good mist coat.
If prepped right you shouldnt get peeling. Make sure to let each coat dry properly before attempting to apply a following coat.
I hope that advice helps you buddy.
Thanks
Paul (of plastermatic)
Following on from my advice and the replies youve had.
Ive never had a problem with a 50/50 water / emuksion for mist coat in the 18 years of plastering.. By the sounds of it the plaster has definitely been over worked/trowed/polished. Plaster primers I feel are just comercialised product. Waist of time in my opinion. So upto you if you want to use a plaster primer. A white wash/ mist coat is quite sufficient.
And tbh any vinyl matt emulsion really. Dont buy expensive emulsion for a white wash it will be a waist of money. Even a basic B&Q cheap home brand white emulsion will be fine. Even if you were going for a silk, or eggshell emulsion for your finish coat. You allways use vinyl matt for a white wash initially.
Thanks
Paul (of plastermatic)
Answered14 December 2019
4
Anonymous user
The best way to seal plaster is to paint it with watered down white emulation
I'm just wondering why the mist coat has failed without seeing photos, normally if it's failed on bare plaster its just small patches? Could be the plasterer has over trowelled and got a polish on the plaster in which case just touch up them areas with primer or even some thinned down oil based undercoat. If its a really good primer/sealer you want Johnstone's paints do one called ultra primer sealer if you want to make sure 100%.
If you mist coat use paint for new plaster. Mcphersons eclipse is best.
Dont dilute 50/50 dilute to manafacturers reccomendation. Eclipse is up to 30% water.
Tikkurilla sell a primer for new plaster.
The mist coat would in all certainty have failed because the plaster was dusty after drying out and that dust should be wiped off before painting
Answered13 December 2019
0
Anonymous user
You could pva for a consistent bond with the paint
Answered13 December 2019
0
Anonymous user
Sounds like a nightmare that I've come across many times a zinsser product for sealing new plaster is fail proof
Hope this helps
