Hot Topics: Dark Spots on Walls After Painting

dark spots on blue wall paint

A quarter-million contributors discuss 120+ topics on our DIY forums, so we highlight active threads to help with popular projects. Hope it helps!

Original Thread: dark spots on walls after application of paint - help

Victor43 - Member

I had to apply some spackle to small areas on the bedroom walls and after applying the paint over the spackle areas dark spots appeared. I tried the same paint (small test area no spackle) on a different room and no dark spot appeared after the paint dried.

I then tried a small test area in the same room where areas of spackle was applied but this time no spackle was applied to a test area and again dark spots appeared. I have included pictures of the dark spots. It appears that the dark spots do not have anything to do with the small application of spackle.

It seems to have something to do with the paint which was already applied before I moved in.

What should I do? The paint which I used does not appear to have primer its an acrylic latex paint.

Thanks!

brown wall with uneven paint

splotchy wall painting

marksr - Forum Topic Moderator

I couldn't tell definitively from the pic.

If it's a stain that is bleeding thru the wall you'll need to apply a solvent based primer [oil base or pigmented shellac] and then paint it. Latex primers do a poor job of sealing stains.

Victor43 - Thread Starter

I'll try out the suggestion of solvent based primer and then paint. thanks.

marksr - Forum Topic Moderator

That last pic helped. It is probably a contaminant that got on the wall and is bleeding thru the paint. If so, a solvent based primer will seal it. It doesn't appear to be a water stain.

Norm201 - Member

As Marksr said. You can use Kilz as an example.

stickshift - Group Moderator

Yep, oil based primer (or shellac-based but I don't think you need that level of sealing) and then another coat of paint.

Good that you did your testing as my first thought was flashing of the paint over the spackle, in which case I would have said a latex primer or even just another coat of paint would probably suffice.

marksr - Forum Topic Moderator

"You can use Kilz as an example..."

..... but only if it's the original oil base Kilz

Victor43 - Thread Starter

Hello. Just an update I've yet to buy the oil based solvent primer as suggested below. What I did find out from an expert that the paint I was using had no primer which may have caused the dark patches or blotches.

So my question is again would it be better to buy a paint with primer such as latex or go with the oil based solvent primer and then buy paint? If the answer again is go with the oil based solvent primer first then does the latex paint need a primer or not?

Thanks

marksr - Forum Topic Moderator

Who was the expert? IMO primer in the paint is just a marketing ploy. Repaints don't normally require primer. Primers are only needed on bare substrates or when there are expected adhesion or stain hiding issues although sometimes a primer can facilitate coverage with certain color changes.

A solvent based primer [oil base or pigmented shellac] does a superior job of hiding stains and is what I would use to guarantee the stain doesn't bleed thru the latex.

papernpaste - Member

Probably the normal look...

after one coat of latex paint. That's my guess. I'm always obsessing over divots and nail pops so, these "discolorations," IMO, are nothing more than the normal after one coat of finish paint. The small areas that you have spackled absorb the finish paint at a higher rate than the other wall surface.

My experience tells me that it is NOT stain bleeding out from the wall. I believe that all that is necessary at this point is a second coat of finish paint. If you have purchased one of the better finish paints, simply apply another coat. The flashing will go away. Before you paint the whole wall again (and it WILL need to be done), take your roller and cover just the spots that you are complaining about.

Wait for a half-hour for them to dry. Then paint the whole wall again. Those spots will then have three coats of paint on them and you'll have a nice, even finish coat. Sometimes, I have to paint the surface three or even four times before the spackled areas don't show like they are now on your wall. It's not a stain. It's just a more porous surface where you have spackled.

marksr - Forum Topic Moderator

"I then tried a small test area in the same room where areas of spackle was applied but this time no spackle was applied to a test area and again dark spots appeared."

That statement points to it being something other than flashing or not enough paint being applied .... or am I misreading that statement?

wildbill7145 - Member

The second pick shows me three spots of flashing a uniform distance away from each other in a straight line. Those would likely be drywall screw patches flashing through. If you're getting dark spots flashing through where there weren't any patches previous, that's just weird. There has to be something on the surface that's flashing through, or there's a contaminant in the paint. But I've never seen a contaminated paint just make individual dark spots.

What paint are you using? Sheen? Like Marksr said, paint and primer in one is a marketing thing and really means virtually nothing.

stickshift - Group Moderator

Latex paint without primer and a separate oil based primer if you need to seal anything currently on the wall.

Victor43 - Thread Starter

Hello and thank you for the responses. I do have another question. When I use the oil-based primer do I have to prime the entire wall or just over the dark spotted areas and then just paint over where the primer has been applied?

Also are these three primers OK to buy? Thanks

https://www.homedepot.ca/en/home/p.p...000402629.html

https://www.homedepot.ca/en/home/p.p...000402628.html

marksr - Forum Topic Moderator

I've used and have trust in Zinnser's primers, I know very little about Behr's coating lineup other than they don't have the greatest reputation.

Spot priming is fine. When you apply the top coat it will dry slower over the primer than the areas without the oil primer but as long as the paint covered it won't be noticeable once dry. I'd spot prime the spots in question, then [once the primer is dry] touch up those spots and then repaint the wall if the touch-ups show.

Victor43 - Thread Starter

Hello everyone. I finally bought the Zinsser Primer Sealer Stain Killer Cover Stain and tried it out. I applied two coats and followed the directions on the can ie second coat in two hours.

But now I tried a small test spot for the flat latex paint and the paint when dried seems to be darker than what I think it should be. I've taken a picture of a piece of drywall with the Zinsser then a spot of latex paint and a piece of paper with no Zinsser with a spot of paint and you can tell that the paint spot on the paper is lighter in color. Any suggestions?

splotchy paint

marksr - Forum Topic Moderator

Latex paint doesn't always cover oil primer in one coat, it will also take longer to dry as the drywall can't absorb the paint. I'd give it another coat and see how it looks after it's had plenty of time to dry.

Victor43 - Thread Starter

Great, thanks Marksr. I'll try another coat and see what happens.