greasy looking patches appearing through emulsioned paint

[Kath123]

I am desperate for some advice. I have been decorating a bedroom. I took off old wallpaper filled patches etc and filled in cracks - in fact followed all advice on here. Three walls are great but the wall which needed the most filling in has turned into a nightmare. I am getting patches appearing all over the wall some areas worse than others. The emulsion is grey. the patches are appearing much darker and almost greasy like. I have rollered this wall with emulsion at least 4 times but when the paint dries the patches reappear. When i filled the cracks i put 2 mist coats and I also used Zinsser stain block on them. What the heck have i done wrong??? it looks awful. I have read somewhere that i might have over sanded the wall - please help. I cannot afford to have the wall replastered. By the way it is an outside walls but it is not damp. The walls were thoroughly washed down so def not wall paper paste. Please please advise.

 

[footprints]

A couple of possibilities come to mind, if the patches are more or less evenly spaced the wall may be plasterboard dot and dab fixing, where the dabs are you can get moisture coming through or condensation if they are colder than the rest of the inner wall.
What paint are you using some like Farrow and Ball have a reputation of being troublesome.
Have you tried Zinsser on the marks, you mentioned treating the cracks with it but not the stains, can you post a photo?
Last possibility unlikely but I have seen it, are you sure they are not shadows cast on the wall, shine a light directly on the wall and see if they disappear.

 

[Kath123]

thanks footprints. The wall is an outside stone wall so unfortunately no plasterboard. The patches are random. Its Dulux paint but i havenet had any trouble with the other walls. no they are not shadows more like a greasy mark which are right opposite the door as you walk in !!!!
I am almost sure i used Zinsser on the patches too because they are places where we took an old train board off the walls and we had to fill in some rather large holes. I will post a pic but it is not very good tbh it looks nothing but believe me they look awful. I have read somewhere that it could be that i have oversanded this area - could this be right??? Nothing would surprise me - this room is turning into a nightmare - especially as i cleverly kicked a brand new tin off gloss on the floor this pm which leaves me with only a half a tin left grrr. Here is the pic.

As i say the pic isnt giving a true image - the marks are much darker than the rest of the wall. Hopw you can help me. Thanks

 

[footprints]

That's a a pain! I doubt it is oversanding because you have mist coated and used Zinsser stain block on them so they should not be sucking up extra paint.
It is possible that the areas you have treated have a better base coat than the untreated and so show differently. Which Zinsser product did you use?
If it is grease I don't think cover stain will do it either Bullseye 123 or BIN are for grease I believe, perhaps BIN would be the one to opt for.
Very fast drying so get it on quick to avoid too many brush/roller marks, wash out tools with methylated spirit or just dump them after.
I know it's a real pain but without seeing the wall before and now the best advice I can give is treat the whole wall with Zinsser, two coats if possible, so your top coat has an even undercoat to go over, many primers (and BIN is one, are known to "flash" through the top coat if only used in patches) otherwise lining the wall might be a solution . Trouble is we really don't know what is leaching out of an old stone wall and can only hope to seal it behind a primer.

Hopefully someone else might have some suggestions on here too.

 

[Kath123]

Thanks again footprint. I used the Zinsser 123 but unfortunately i only did the areas that i had patched up. So its 2 coats of Bin then. Do i need to sand wall down first ???? Thanks for advice again.

 

[footprints]

Might be worth giving it a light sand but only a couple of passes over with a bit of sandpaper don't go too hard at it just a light rub to remove any glaze or odd bits stuck to it. Wipe down to remove dust and do the zinsser.
Please me know how you get on

 

[lostinthelight]

Had there prevously been a fireplace/ chimney in the wall?
litl

 

[Kath123]

Yes this is an old chimney wall litl!

 

[Kath123]

Footprints i have done what you suggested and given it a light rub down and given it its first coat of Zinsser - will keep you informed . This wall has taken me longer to do than all of the rest of the room together. Typical its the wall that catches the light - much more than the others!! Never mind as long as it turns out ok. Thanks

 

[Kath123]

Footprints - just to let you know that after 2 coats of emulsion i do not have any greasy marks on the wall. Thank you so much for your advice you are a life saver. Thank you

 

[footprints]

Very glad to hear it! Nice to see your problem sorted, thanks for the update