9

I'm painting a room that had previously been wallpapered. The walls are veneer plaster coated, so the paper was easy to remove and clean the plaster. However there are patches for wiring, dings and other artifacts of sloppy plastering that I've covered with regular joint compound.

As I start painting (latex) I find that unless I'm really quick and wet across the compound, it starts to come up and ruin the finish.

Should I be spray priming? What do others do about this issue?

  • Good question. I always cover those spots with a brush first, as the rolling is when it comes up for me. The downside is that it can alter the texture of the finished wall. – Evil Elf Apr 8 at 12:37
  • @kris, answers go down there. – isherwood Apr 8 at 13:21
12

A primer is recommended for joint compound. Using a primer seals the mud and actually uses less paint with a even finish in the long run.

  • 4
    The most significant benefit is more even sheen in the finished product. – isherwood Apr 8 at 13:19
4

If you find you're doing a lot of patches, buy some "new drywall" primer. It's cheaper and helps you get the new compound ready for paint just as well (it's also latex). It generally is only available in gallons, though (with the assumption you've done a whole room in drywall)

If you're not doing a LOT of patches, consider using a better patch. Joint compound is different from vinyl spackle, and some types of spackle come pre-primed now.

  • 1
    Commonly called PVA Primer, and it can be tinted (like any other primer) to match the paint color if you're using a color other than white. – JPhi1618 Apr 8 at 15:20
  • So you are saying use spackle instead of mud? – DaveM Apr 8 at 15:26
  • 1
    @DaveM For smaller patches, yes. Spackle doesn't shrink and tends to be a bit stiffer, so it fills larger holes better. And 3M, for instance, makes a pre-primed spackle – Machavity Apr 8 at 15:33
4

Huh? Of course you will. Always.

Anytime you put topcoat paint on a surface that is inconsistent, it will show inconsistent results. The topcoat will react differently to different surfaces, leaving a different texture that will be noticeable.

That is the entire point of primer. You paint primer over the mixed surface, the primer seals it, and after 1-2 coats (possibly with some help from sanding or filler in between primer coats) you have a surface that is uniform (consistent/the same) - it's all dried primer. The topcoat applies evenly.

Primer also causes the color to be uniform, because otherwise, underlying different colors will print through (most architectural coatings are near-white, and white paint isn't that opaque).

Primer is optimized to do this. It's also cheaper. Paint can do this too, but it'll take ridiculous numbers of coats of it.

  • Sanding a primer is not a concept I'm familiar with – DaveM Apr 8 at 23:02
  • @DaveM, primer can sometimes make issues worse, or it can react a little with the surface. To get a really even coverage, sanding rough or "odd" spots and reapplying primer can help the end coat. – computercarguy Apr 8 at 23:58
  • Thanks, understood, it also gums up my sandpaper. – DaveM Apr 9 at 0:12
  • @DaveM because you're sanding too soon. Wait for it to dry. Yes, applying primer can make a few surfaces bumpy, but, most likely paint would do the same thing. Primer "springs the trap" as it were, then freezes it so it won't do it anymore. At least that's the idea. Also, you often sand just because the surface was already rough and that becomes more visible once primer gives it a uniform appearance. – Harper - Reinstate Monica Apr 9 at 0:43
1

It sounds like the joint compound was applied over a paste residue that is reactivating from the moisture in the paint. It can be very near impossible to get all adhesive washed off of the surface. That is why I always use a sealer before patching. Best one I have used is Gardz by Zinnser. It creates a thin barrier coat that locks down containment’s on the surface. After it drys do your patching and sanding followed by spot priming of repairs with same product. –

  • I've seen that, but I'm pretty good about getting it clean. If I find a patch I missed, I immediately scrape off the wet paint and glue from the spot, and repaint. – DaveM Apr 8 at 15:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.