Primers

Why do I need a primer?

Paint cans have Paint & Primer in One written on them.

If paint is self priming then why do companies sell primers?

The simple answer is Paint and Primer in One is a misnomer.

Paint and Primer in One only works on similar surfaces ie. Water based over water based. Colour tone change is not drastic. The sheen level is also similar ie. a combination of flat or eggshell over, under each other. If you are painting over semi-gloss or gloss you should use an adhesion primer and this also applies for painting over oil paint.

The exception is an oil based primer. You can paint latex or oil over an oil based primer.

Drywall:

When you have sanded brushed down or vacuumed the surface it should be primed with a dry wall primer. This particular primer is thinner than other paint to promote soaking into the surface and forming a “key” for your finish paint to build upon. It is recommended to apply two coats.

After the first coat you can see areas that require further filling or sanding. A good practice is to have a light source and rake it across the areas that will have pot lights, wall sconces or table lamps shining on the areas. Better to deal with these areas now before you are finished and put furniture in. Sandpaper the patches and prime the drywall again. This will give your finish coat the best surface to look its best. Finish paint is just that Finish Coats.

Trim:

New trim can come raw or with a primer on it. I would always recommend rubbing it down with a cleaning agent before proceeding with any painting. Just being handled leaves oils from skin that paint will not adhere to.

Bare softwood trim can be primed with a water based primer. When you apply the first coat it will raise the grain. Sandpapering before you prime will not get you a fine finish. Prime, fill any holes or imperfections. Sandpaper with a medium grit 100 to 150. Dust off the surface and apply a second coat of primer. This will ensure a good finish.

Bare hardwood should be treated the same way only use an OIL primer. It will smell more and take longer to dry but it is the way to go. Hardwood tannin will seep through water based primer and paint and takes on a smoke or water stain appearance. You may have seen this on finger joint trim where a piece of hardwood got mixed in and the water primer failed to hold in the tannin.