Emulsion bubbles?

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Just in process of trying to tidy up a spare bedroom. It was painted with a hideous purple silk emulsion, and was a good smooth finish. We have painted over it with good old matt magnolia, and in some places there are little bubbles starting to appear. All walls have now had 2 coats of matt, and whilst one wall bubbled after 1st coat, another has only done it after the 2nd coat! It seems to be the purple paint that's bubbling rather than the magnolia, but no idea why this is happening and why it's only in certain places in the room. Any suggestions would be welcome, both on why it's happened and how to get rid of them (I assume just sanding them off and repainting again?). Thanks!
 
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Do you know for a fact that the purple paint is silk emulsion ? Also, what does that mean "Good old matt magnolia" ! What type of make & type of emulsion is it ? Anyhow, blistering in the way explain can be caused by many reasons and heres the two main common ones, 1/ Silk emulsion been applied directly over new/bare surfaces without thinning, can cause blistering when overcoated at a later date. 2/ Dreaded One Coat Emulsion can also do this (blister) BUT IT ONLY HAPPENS WHEN ITS OVERCOATED AT A LATER DATE, the stuff should be banned !
 
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The water in the paint your using has soaked through into the stuff below and probalby caused it to buble (bit like it does when you wet a wallpaper)

The cause can be a lot of thing

The bubbles, should dry back when the paint dries and the surface tightens up.
 
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Re 3rd Eye's questions:
I know that the purple paint was silk because I painted it about 5 years ago (I know I said it was hideous, but the wife liked it at the time!!). It was B&Q - the stuff that comes in a transparent tub).
The magnolia I'm using is B&Q value matt emulsion (cheap but not too nasty - I've had fairly good results with it before).
 
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In my opinion using B&Q value matt emulsion over silk is a no go. I would personally never do this. The reason is cos its like putting Dulux Supermatt over Dulux Vinyl Silk, this cannot be done as it causes many probs. I know you say the prob may be with the silk bubbling, therefore if so then what did you paint over when you used the silk 5 years ago ?
 
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Don't know what it was except it was very dark green and was definitely not a matt finish. As I said, the purple went on really smooth over the green and has looked ok for the last few years. It's only now I've come across the problem. What seems wierd is that of the whole room we've painted, the bubbles only appear in small areas on different walls, not all over.
 
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Ar they about 1 cm across? and have they gone down now the rooms dry?
 
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Zampa, no they are really small maybe 1mm bubbles (some maybe slightly bigger but not much) and no, they haven't gone now the room's dry (unfortunately!!). On the bright side, apart from the bubbles, the rest of the room looks pretty good!
 
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Gcol, fair point!
They may be slightly bigger than 1mm but not much - problem is that they are in patches and there's a lot of them in a patch.
If there was only one tiny bubble on a wall, I wouldn't be wasting my time asking what it was, would I ?
 
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Vinyl Soft Sheen can do this what you explain (i.e. small bubbles appear). But this happens when trying to overcoat to quickly (even when following tins instructions). To be honest it seems to me that your previous silk emulsion that was done 5 years ago has been coated over a shiny surface OR over an One Coat Emulsion and is resulting in blistering, as the surface (if shiny) should have been rubbed down prior to overcoating with silk 5 years ago to create a key. Also excess paste that has been emulsioned over can also cause blistering 5 years later.
 
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In that case its airation..little bubbles like pinheads...caused by a combination of the roller and the paint...oh and the fact you were going over silk..i bet you didnt have any in the the brush work

It has 'foamed' up the paint being home brand can do this..and being a smooth almost sealed surface the paint will just bounce about on the surface as opposed to absorbing in if it was matt.

And was the room really warm?..that doesnt give the bubbles a chance to pop...so they dry like that...give the wall a good rub over to get rid of hem before you do another coat.

The same effect can happen on an outsdie on a hot day if you rolling paint thats thin or has been ****ed out to much
 
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sparklymarkly said:
Gcol, fair point!
They may be slightly bigger than 1mm but not much - problem is that they are in patches and there's a lot of them in a patch.
If there was only one tiny bubble on a wall, I wouldn't be wasting my time asking what it was, would I ?
My apologies, I thought we were talking about bubbles under wall paper, not in the paint surface. Do what Zampa says.
 
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Zampa, should have mentioned that I didn't use a roller - all done with a very wide brush (I'm not v.good with rollers - I always press too hard and make a t*ts of it by scraping the wall with the roller frame, so prefer brushing).
Interesting what 3rd eye said about the problem being with the original green paint; I remember when we painted over it, it was bl***y hard work as the brush "dragged" really badly. However, when done, it did look good (except the colour!!).
Main question now is if I sand out the bubbles and do another coat, will they come back?
 
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Back t the drawing board! :(

Main question now is if I sand out the bubbles and do another coat, will they come back?

I dont think you have much choice now..are you any good with a digital camera?
 

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