Stain coming through after mist coat

[Max Power]

I have applied two mist coats and this stain is still coming through.

I have no idea what it is. Its not raised or anything.

Am I right in thinking that I need to use something like Zinsser Bin to block this stain before I apply the top coat?

 

[JohnD]

Might it be PVA glue spilled by the plasterer?

Scrub it with water. PVA glue is water soluble so the paint will peel off it.

 

[Chivas69]

Certainly looks like pva. If it hasn't indented the plaster it should cover fine with the top coats. Just give it a little sand and mist coat the area again.

 

[JohnD]

Clean it off and forget about it for ever.