Primer blistering

[rhysjc]

Hi all,

Yesterday evening I applied a coat of primer in our spare room. All went on fine but wasn’t totally happy with the coverage, the walls have had a fair bit of work done to them and so decided to do a second coat this afternoon. However in some spots the primer has blistered as you can see in the picture. The worst affected area is at the junction of two external walls so I suspect it may be an issue of the wall being too cold or perhaps some condensation there?

All ears for any theories and more importantly any remedies! Currently thinking sand back those areas and apply some zinsser peel stop? For what it’s worth I did prep before the first coat by sanding down, dusting and cleaning with some sugar soap. I didn’t do so for the second coat

 

[Wayners]

Whats under the paint? Was it old emulsion?

 

[rhysjc]

Whats under the paint? Was it old emulsion?

Yeah old emulsion in the area that’s blistered. The previous owners had the walls everywhere reskimmed. I am fairly certain they didn’t mist coat as there’s plenty of flaking paint in other rooms. Potentially that’s what’s causing the issue but the paint wasn’t flaking in that area previously…

 

[Wayners]

Emulsion degrades over time for a few reasons. Maybe it's lost adhesion and you applying a fresh coat caused this trouble.
I've had it many times painting over a perfectly good surface.

 

[rhysjc]

Emulsion degrades over time for a few reasons. Maybe it's lost adhesion and you applying a fresh coat caused this trouble.
I've had it many times painting over a perfectly good surface.

I think I’d be scratching my head forever trying to figure out the cause, to be honest. It is odd it was fine on the first coat though…Do you have any suggestions as to how I can sort it?

 

[Wayners]

Scrape off
Use a wallpaper scraper. The one's with razor sharp blade.
Then sand.
Fill, prime again.

 

[opps]

I would be looking at mist coats that were not initially thinned sufficiently last time around. You might be able to coat the walls with Zinsser Guardz. I haven't ever used it but I believe that @Wayners has, so I will leave you let a fellow (competent) decorator advise you further.

Personally, I would sand all of the paint away, but if you don't have access to the correct sanders, Guardz will be the path of less resistance.

 

[rhysjc]

I certainly don’t have the correct sanders for that, nor the will power! Interesting - I would have thought peelstop here rather than Guardz? Not clear to me what the difference is in fairness

 

[opps]

I certainly don’t have the correct sanders for that, nor the will power! Interesting - I would have thought peelstop here rather than Guardz? Not clear to me what the difference is in fairness

Fair play. Both @Wayners and I are professional decorators. I haven't used either product. I will leave you to defer to his superior knowledge of each of the two products.

Best of luck- oh and please let us know how you eventually get on it will help others... and perhaps me too.

 

[rhysjc]

Absolutely will do! I try to make a habit of coming back to my threads and updating. Sometimes good news sometimes bad

 

[Wayners]

I've never used peelstop tbh. Never needed to although it's a brilliant product when used to solve a problem.
If you use peelstop it binds the edges and stops the fresh wet paint getting under and lifting original paint.
You can't paint it over bubbles to remove them.

Re bubbles.
Putting a durable emulsion over a dry contract emulsion will causes bubbles like that.
I put valspar premium over crown breathless emulsion and got a few bubbles. Durable emulsions have resins that don't like dry surfaces and the stress tension in the paint causes bubbles.
By sealing the surface durable emulsions settle and naturally dry with no problems.
If you follow the application advise you can use some ( not all) durable emulsions as a mist coat but you can't mess with it. Any back rolling will effect the adhesion so I tend not to use it for that purpose.
With so many formulas and resins you can't just lash on and expect no problems it seems these days.
Many pros stick to a system and manufacture they know as much as possible to avoid unexpected problems.

 

[rhysjc]

No absolutely wasn’t expecting to paint the peelstop over and have the bubbles disappear! I was suggesting I could put some on after scraping the bubbles off and sanding.

To your other point, this was my second coat of the same primer which bubbled. First one yesterday evening was fine, second one today has bubbled. I can only assume there was some dust or the surface wasn’t quite dry and that’s what’s happened here, as you wouldn’t expect a second coat of the same product to have any issues! I think as a first try I’ll just sand back these areas, fill and spot prime. Will report back!

 

[Wayners]

I'd be interested to see what's under.
So many bubbles

 

[rhysjc]

I’m hoping underneath will be my original coat of primer! Would be odd if that had bubbled up too as it was totally dry

 

[rhysjc]

Just a little update for anyone following. The blistering definitely got better once the primer has fully dried. I’ve scraped off what I can and sanded the areas, and have applied some Peelstop which seemed to be the consensus on YouTube. Once it’s dry I’ll fill and sand. I’m using toupret ready mixed fine surface filler which supposedly doesn’t need spot priming. So hoping I’m ready for a topcoat after all that!