On 24 Oct, 09:49, Stephen wrote:
Hello,

As you may have read in my other post, I have been rollering a
ceiling. The ceiling was plastered and allowed to dry and then I
painted it with Blue Hawk plaster sealer from B&Q and allowed that to
dry. When I rollered the ceiling 99% went on fine but in one or two
patches I got some tiny blisters.

I made the mistake of scraping the blisters but this made them worse
because they kept blistering at the edges so I scarped back more and
got bigger and bigger bald patches!

I left some blisters alone and to my surprise, when the paint dried,
they disappeared completely.

What caused the blisters and how can I avoid them in the future? Was
the plaster not sealed adequately; I've never seen them on any other
ceiling I have painted.

I have over painted the craters that I scraped out and they are
staring to look more hidden but they can still be seen when the light
hits them from a certain direction. What's the best way to remove
these: some filler?

Thanks.

This can occur if the plaster is dusty in places, and the emulsion
does not "stick".
But you say you sealed it ? Did you miss a few bits ?
You can check with a light at a low angle where the sheen of the
plaster sealer can be seen.
Also, the thick emulsions can be worse for this.
Simon.