Paint to cover stains

shandy1

Hi. The wife and I recently moved into our first home.
I stripped the wallpaper in the bedroom and living room and hung 1400 grade lining paper. I left a 1mm gap between some and filled it with decorating caulk, then sanded it off. (Should've butt joined it all).
I then painted with dulux Matt emulsion, 2 coats.

Where I filled with caulk and sanded, there is a shimmer kind of stain that runs down the joint and it won't go away. I maybe should've put a primer coat on first but I was told 2 coats of emulsion would be sufficient.
I'm not sure why its stained as I thought it was meant to be paintable.
How can I fix this issue? Would a stain cover paint like zinsser cover it? Would I have to cover the whole wall so it's not uneven?
I really don't want to tear it down and start again, or cover it with another wallpaper as we have a feature wall already wallpapered.
Hope someone can help!

so_very_confused

In my experience Zinsser bin covers everything. Love the stuff!

shandy1

I'll maybe try that then. Any idea if I'd need to do the whole wall?

murphydog999

I asked the same question to a builder friend of mine the other day, he recommended a product called stain block. Haven't tried it yet, I think Screwfix are one stockist.

southcoastrgi

Not disbelieving you but are you sure it's a stain, my guess is that it's showing as a different surface, i.e. Your lining paper isn't smooth & the caulk is, you will get the same if you use filler & look at it in a certain light, as a side note you can't really sand caulk, that is used as a gap filler like on the top of a skirting board & smoothed with a wet finger or tool just like you would silicon, what you should have used was something like easyfill

Cornucopia

Stainblock is excellent - even the cheap one from Toolstation.