A primer is a primary coat or undercoat that is put on a surface before painting. It sticks to just about anything and helps paint stick to it. Primer creates a smooth, consistent base layer and can solve a multitude of potential painting problems such as stains, moisture damage, bare wood or painting over dark colors.
You don’t need a primer if you are repainting a surface that is in good shape. As long as there is no peeling or chipping, you can just paint right over a previous color.
Unfinished surfaces such as bare wood, drywall, metal and concrete must always be primed before painting. Choosing the right one will make your paint job look better and last longer.
If you are painting over bad stains on the wall like rust, crayon, grease, mildew or water damage, a primer such as Kilz2 is the solution. Kilz2 Latex is a fast drying water-based sealer that not only blocks stains but can also suppress odors such as cigarette smoke. It also comes in an oil based version, but I don’t like the smell or the clean up. I always choose water based as long as it does the job just as well.
Kilz2 provides a mildew resistant coating and is a good choice for high moisture areas such as kitchens, bathrooms and laundry rooms.
As long as the surface is clean and dry, Kilz2 can be applied to brick, drywall, stucco, masonry plaster and wood. As with any painting job, you have to wash the surface to be painted first.
DRAMATIC PAINT CHANGE
Making a drastic change to the color of your wall will require multiple coats of paint and a primer is essential to achieve the depth of color you envisage. It is common practice to use white primer for lighter colors and a grey tint with darker colors.
The paint company Sherwin-Williams has found that many of its deep, bold and vivid colors are enhanced when applied over a grey-tinted basecoat. To improve color depth, they have introduced a Color Prime System that starts at a light grey and gradually deepens to a dark grey. The technology is based on how color pigment absorbs light and aims to achieve true color that accurately matches a paint chip.
The mud on the seams of drywall absorbs paint differently from the rest of the drywall. The seams will stand out and be obvious unless you use a primer first. In this situation you need to seal the drywall to even out the porosity and create a solid foundation for the paint. Gardz by Zinsser does an excellent job of bonding to the drywall and smoothing out imperfections. It is water based, which I always prefer, goes on fast and dries quickly. The consistency of the primer is very watery, so make sure the product is well absorbed by your roller before applying to the wall or it will drip. I would also suggest wearing gloves during application, as Gardz is very sticky and difficult to get off your hands.
Spot priming means you apply a primer only to the spots that need it, such as a stain or repair. If you have sanded down to a bare surface, you will also need to apply primer to those areas or the paint won’t stick. Feather sand around the edges with a fine paper to make sure the surface is smooth and even.
If the paint is in good condition there is no need to prime. If paint is chipping or flaking, sand down to the wood and spot prime where needed. Check to see whether your trim is painted with an oil or water based paint. To do this, dampen a piece of cotton wool with an acetone based solution such as nail polish remover. Wipe the surface and if any paint comes off, it is water-based.
Since oil-based paints are gradually being phased out for environmental reasons, you may want to change your oil based trim to water-based. To do this it is essential to prepare the surface properly. Clean, sand thoroughly, clean again, then apply a water-based primer such as Kilz 2 or Zinsser’s Bulls Eye 123. When dry, apply 2 coats of good quality acrylic water-based paint.
If you put latex on top of oil without using a primer, you will be able to scrape the paint off with your fingernail.