Marks showing through plaster/paint from plasterboard joints

JustAnotherSaver

I'm wanting to know
1) what these stubborn marks are
2) how to get rid

In the photo you can't see it so well. For some reason the photo didn't pick it up but in person it's noticeable.

It's some weird mark/stain that is on the plasterboard joints. It didn't run the length of the joint, just a smallish section. They'd taped up the joints so i don't know what this is all about



I mist coated with a 1:1 ratio
I've since gone 2 coats with a 1:5 ratio. Laid it on fairly thick and it's still showing through.

Why is it being so stubborn?

DRP

JustAnotherSaver wrote: »

I'm wanting to know
1) what these stubborn marks are
2) how to get rid

In the photo you can't see it so well. For some reason the photo didn't pick it up but in person it's noticeable.

It's some weird mark/stain that is on the plasterboard joints. It didn't run the length of the joint, just a smallish section. They'd taped up the joints so i don't know what this is all about



I mist coated with a 1:1 ratio
I've since gone 2 coats with a 1:5 ratio. Laid it on fairly thick and it's still showing through.

Why is it being so stubborn?

I can't really see much in the photo.

But, Why are you still diluting the paint?

One mist coat (1:1 seems a bit too dilute to me, I usually add about 20% v/v) to seal it, followed by painting as normal, is how i've always done it.

I'm not saying this is causing your issue, but diluting your paint may be a factor.

JustAnotherSaver

Yeah it's a really bad photo. Quite annoying.

In person it's very noticeable.
On my phone it's fairly noticeable
On the PC it's kind of tricky to see
Then i don't know if it's after resizing or uploading but i can barely see it myself in that picture now.

I'll try again........



As for the diluting, i did much reading online which seemed to come back with a 1:1 on the mist coat. Various sources.
It was fairly wishy-washy though, such as when people say sand down over polished plaster, but never actually elaborate on to what grit to use.

But as for why i then went with 1:5 ratio on the coats - that's what the Dulux SuperMatt tub states to use for subsequent coats (yes 1:1 is more watery than they suggest)

Kiran

I can't really see anything in the photo but does it feel any different to the rest of the wall? If not, just stain block it and decorate.

Grenage

After one mist coat, I'd just crack on with the top coats.

My last place needed an awful lot of filler; after filling and sanding flush, I'd use one mist coat 70/30, then locally brush a couple of neat coats over the filler and surrounding area. I'll then roll the wall a few times as normal.

No flashing or marks ever came through that.

JustAnotherSaver

On a different wall i had to fill a section.

I made sure it was smooth & flush

It wouldn't take the paint the same, so i brushed over the filled area as per advice. Tried my best to brush it out and 'feather the edges'.

If you look close you can still tell that it was brushed with the rest rollered

DRP

JustAnotherSaver wrote: »

On a different wall i had to fill a section.

I made sure it was smooth & flush

It wouldn't take the paint the same, so i brushed over the filled area as per advice. Tried my best to brush it out and 'feather the edges'.

If you look close you can still tell that it was brushed with the rest rollered

But did you then roller over the whole lot? IF so, do another coat.

cyclonebri1

Are you sure you can't see a shadow from a dip at the joint?
Fill and sand and paint

brandydog

if its brown touch up with oil paint ie undercoat then emulsion should be ok

victor2

I've used a solvent based primer/undercoat over water stains coming through plaster, then painted over it with regular emulsion without the stain reappearing. Stain block does the same I believe, but I had some primer I could use so it was the cheapest way for me.

Without that, it doesn't matter how many times you paint over it with emulsion, the stains come straight back.

JustAnotherSaver

Why would there be water stains (IF it's water staining)?

I had a look today & it actually runs along the joint. Not the full length, but it is along where one plasterboard joins another.

Also if i hit it with either stain block or oil based undercoat then isn't this going to flash through subsequent full coats?