Paint bubbles immediately after painting

[terribleateverything]

I was putting the second coat of white paint on my walls today and immediately after painting a small patch of the wall went all bubbly:

I prepped the walls properly by washing and sanding (admittedly I didn't do that between coats) and bizarrely the rest of the same wall looks absolutely fine. Could it have been the heat (south facing room), or maybe it was because I'd just opened a new tin of paint and perhaps stirred it a bit too vigorously and therefore introduced air bubbles? Any ideas welcomed as I'd like to avoid it happening again.

Anyway, fast forward half an hour or so and they've mostly disappeared:

Is there anything special I should do before putting the next coat (colour rather than white) on? I'm guessing bubbling isn't ideal for adhesion, so don't want to slap on the much more expensive finishing coats just to have to redo it all again. If the bubbles had remained I would have likely scraped/sanded/filled and painted again.

 

[terribleateverything]

Oh I should probably add very unlikely to be moisture in the wall, there's no plumbing anywhere near it and it's not rained in weeks

 

[Chivas69]

I usually find this is grease spots or someone's opened a can of coke up the wall. It is more than likely underneath the original wall colour though and when your put your new wet paint on top the water brings the spots back out. They then go back down once dry.
You can sand beforehand but it will only react to the wet so won't stop it. The fact it goes back down means you shouldn't really need to worry about it. I think the only way of getting rid of it would be to sand off right back to bare plaster and there's no point if it's drying flat.

 

[terribleateverything]

I usually find this is grease spots or someone's opened a can of coke up the wall. It is more than likely underneath the original wall colour though and when your put your new wet paint on top the water brings the spots back out. They then go back down once dry.
You can sand beforehand but it will only react to the wet so won't stop it. The fact it goes back down means you shouldn't really need to worry about it. I think the only way of getting rid of it would be to sand off right back to bare plaster and there's no point if it's drying flat.

Thanks! Although the first coat went on fine, which is the most confusing thing...

 

[Chivas69]

It's just the combination of the two coats. The first coat could still have a slight bit of moisture in it.

 

[terribleateverything]

Now it's doing it on another wall! It's gotta be the heat, surely

 

[Chivas69]

Burst one of them and see what colour is behind it or uf it's bare plaster.
Or just keave it if it goes back down, lol

 

[terribleateverything]

It's the same colour as the first coat when I pop the bubble. Gonna try painting at like 6am tomorrow when it's much cooler, hopefully that'll work...

 

[lostinthelight]

Under where the bubble were will never be bonded to the previous coat so the next coat will raise the bubbles again.

 

[terribleateverything]

Under where the bubble were will never be bonded to the previous coat so the next coat will raise the bubbles again.

So what do I need to do? Sand it all back?

 

[lostinthelight]

Sorry I'm not a pro so just leaving them to shrink back, which they usually do, has been good enough for us . There are some pro decorators on here that can guide you on the correct method when they turn up.

 

[Chivas69]

You can prime the wall before painting if you want. You could use a different roller. You could scrape off every bubble when they show up, then fill and prime and re paint. You could get a sanding machine and go to town.
Or you could let them all disappear once again and grab a beer out of the fridge.

 

[terribleateverything]

You can prime the wall before painting if you want. You could use a different roller. You could scrape off every bubble when they show up, then fill and prime and re paint. You could get a sanding machine and go to town.
Or you could let them all disappear once again and grab a beer out of the fridge.

Unfortunately the ones from last night didn't disappear, and it's happening on every single wall. Popped latest ones and can see original colour, on the back of the skin??

Might be time for a primer

 

[Chivas69]

As in, the original colour before your new colour. This does seem like the original colour was painted on top of moisture or droplets of grease or fizzy drink etc. Now each time you re wet the surface the bubbles are showing. This is where the original paint didn't adhere properly.
It's a shame they are not going down now.
One thing to try is to pop the bubbles or scrape them away, then let it dry and give a good sand down and maybe a little bit of filler if the pott marks are showing.

 

[terribleateverything]

As in, the original colour before your new colour. This does seem like the original colour was painted on top of moisture or droplets of grease or fizzy drink etc. Now each time you re wet the surface the bubbles are showing. This is where the original paint didn't adhere properly.
It's a shame they are not going down now.
One thing to try is to pop the bubbles or scrape them away, then let it dry and give a good sand down and maybe a little bit of filler if the pott marks are showing.

It was a kids room before we moved in, so that is very very likely.

Is it worth also spot priming and, if so, with what? Zinsser 123? BIN? I think I've got some old peel stop in the garage.