Bathroom Ceiling about to fall down

WIAWSNB

Check out your Facebook Marketplace. Very good chance you'll pick up a new or part-used tub of white emulsion for little, especially if you are not in a hurry. 
Post a pick of the 'Base' you have. Where did it come from? And what did you ask for?
In any event, give the ceiling a good wipe over with a damp cloth and a household cleaner to first try and remove as much of the stain as you can. Let it dry fully.

bjorn_toby_wilde

Pingu1 said:

Well it says Base A, I don't fully understand what it is.

I suspect it’s plain white Matt emulsion, which they use as a base. In other words, they add tints (dyes) to it when they’re paint mixing to produce the coloured emulsions.

It’s not more primer.

bjorn_toby_wilde

WIAWSNB said:

Check out your Facebook Marketplace. Very good chance you'll pick up a new or part-used tub of white emulsion for little, especially if you are not in a hurry. 
Post a pick of the 'Base' you have. Where did it come from? And what did you ask for?
In any event, give the ceiling a good wipe over with a damp cloth and a household cleaner to first try and remove as much of the stain as you can. Let it dry fully.

OP has already overpainted with a stain blocking primer so it should be ready for the emulsion.