Which primer to use?

I'm re-painting my bathroom, I had to repair an area on the wall with dura bond and then plaster. The wall I'm painting has a satin enamel on it and I'm re-painting it with satin enamel. I need to primer over the area I repaired and have 2 primers, PVA Drywall Primer and Kilz Premium water-base primer, does it matter which one I use? Also, do I just prime the area I fixed or the whole wall to make it blend in? Thank you.......

 

I've never used the KILZ water based products, so I don't know how good they are.

If it were me, I would just use the PVA primer over the BARE plaster repair. You prime over bare materials like bare plaster, bare drywall, bare wood and bare metal.

You paint over paint.

 

Either primer should work although I've heard of bonding issues with the latex kilz. I never use the latex kilz because it's a poor stain sealer and there are better primers available. As noted above, only the repairs need to be primed.

How many coats of enamel do you intend to apply? If only one, it would be a good idea to spot paint over the primer [after it's dry] with the latex enamel. That way the enamel should hold an even sheen over the repairs. Is there any texture on the walls? even roller stipple might need a light texture to make the repairs invisible.

 

When I called the BEHR paint company they told me to primer the plaster spot first, let it dry good, then prime over the whole wall and plaster spot again to make it uniform. I'm painting this wall a dark green with satin enamel, he said because of the dark color the wall should be completely primed so the paint dries at the same sheen. I'm going to give this wall two coats of paints seeing thats what the other 3 walls took to cover evenly, that was a lighter green. There is no texture on the wall, just 15 yr old latex paint when I put the bathroom in. Its only a little 8x8 wall, you think I should play it safe and primer the whole wall or just the plaster spot. The plaster spot is about 3' long and 2' high. Thanks

 

I don't use Behr coatings so I can't attest to how their coatings work [cover,dry,etc] When a wall has areas of even porosity the paint can dry/cover different in those areas. Using SWP's mid grade or better paint - I wouldn't bother with priming the whole wall. Since it's a short wall, you could make an argument for either method - won't take long to prime or it's a short wall if you need an extra coat of finish.

 

Grantiman:

I suspect that whomever you talked to at Behr probably got hired to answer phones just a few days ago and was given a two day training course on paint. He's giving you good advice that you may want to prime the whole wall, but he's got the reasoning all screwed up.

Certainly, you should prime over the bare plaster. However, the reason why priming the whole wall may be to your advantage has nothing to do with sheen, and everything to do with hide. That's because high hiding primers have lots of white titanium dioxide pigment in them, and titanium dioxide is a high hiding pigment (second only to black). Since titanium dioxide hides better than Phthalocyanine Green (the universally used green pigment in house paints), then you can hide the existing colour of the wall better with one coat of high hiding white primer than you can with a coat of green paint. That is, you can save labour by putting on one coat of high hiding primer and two coats of green paint instead of four coats of green paint.

And, to help matters along, you might want to have that white primer tinted with green colourant to make a greenISH primer. That will give you a head start in turning the wall the desired green colour. That will actually improve the hide because you still have the same amount of titanium dioxide in the can to reflect and refract light, but now you're adding dark green to absorb much of that reflected and refracted light.

Bear in mind that when people repaint the walls and ceilngs in their houses, they repair nail holes and other areas of damaged plaster (just like you did). But, they don't prime the entire inside of their house before painting. They only prime the bare plaster repairs, and then paint over everything. If getting the sheen uniform was the issue, then everyone would have to prime over paint all the time. You really only need to consider priming over paint if: A) you're wanting to paint over an oil based paint with a latex paint, in which case you'd prime with an oil based primer first, and B) you're wanting to repaint the wall a different colour, and the colour you've chosen doesn't have very good hide, in which case you'd always be best off to use a tinted high hiding primer. The latter instance applies to you.

Cut in around the perimeter of your wall with a sash brush, and then fill in with a roller. If you're using a latex paint, you can simply store your brush, roller and tray in plastic bags and/or in the fridge (not the freezer) between coats. Once the paint warms up, it will spread properly.

Once you've brushed around the perimeter and rolled the middle, give the wall 24 hours to dry and look for any "picture framing" effect around the perimeter of the wall. If you see that, it means that you're not getting complete hide with one coat. That's because the brush coat and roller coat will overlap at the perimeter of the wall, resulting in a band of increased colour density there. Keep applying coats of paint until you no longer see any such picture framing. If you can't see any difference between n coats of paint and n+1 coats of paint, then both are hiding the underlying colour completely, and adding more coats of paint won't make any visible change in the colour density.

If you do prime the whole wall, then you may need to check to see which primer hides better first. Simply use a Q-tip to paint a bit of each primer on a paper swatch of the paint colour you intend to use, and see if one is clearly better than the other. Not all primers have plenty of titanium dioxide in them to give them high hide. The job of a primer really isn't to hide the substrate, it's merely to stick well to the substrate and improve the adhesion of the top coat. Primers do that by having huge rocks in them almost large enough to see with the naked eye. That makes the primer dry to a rough surface so that the top coat sticks better. But, since those same rocks also plug up the surface porosity of bare plaster and bare drywall, almost all interior latex primers will call themselves a "primer/sealer". Still, those rocks don't improve hide as much as titanium dioxide pigments do, so to get the primer you want, you need a HIGH HIDING primer/sealer. So, you may have to buy yet another primer. Or, tint what you have, but give it another coat of tinted primer.