Third coat of primer, or paint?

Question

I have been slowly repainting rooms in my house. The walls are sheetrock, last painted over 20 years ago with many layers of paint from multiple owners. Some of the rooms have dark wood trim (which I'm also painting).

I've noticed that it takes a minimum of two coats of primer and two coats of paint to cover the old paint color and spackle, which is fine. I use Kilz primer and Behr paint usually (latex). Often it takes a third and sometimes even a fourth coat of paint.

This is the primer:

Here's the question. Given that primer is cheaper than paint, would I be wise to always begin with three coats of primer? Would that reduce the number of needed paint coats? The color is white.

Answer 1

I've never painted a room white but the main purpose of primer is to seal porous surfaces like fresh sheetrock. KILZ 2 specifically has stain blocking properties as well. If you have adhesion issues, particularly on semi-gloss walls, then something like PPG Gripper is a much better choice. It sounds like you're using primer for the sake of using primer.

I think you would get better results by paying more for a better paint. I personally love Behr Ultra or higher; $40/gallon. I think this would let you get away with just two coats of fresh paint and skip the primer. Unless of course you value your time at $0.

Additionally, the more paint you can roll in one try, the better. If you're using a 3/8" nap then try a 1/2" nap instead.

Answer 2

You need to use enough coats of primer so that the surface is consistent.

Imagine you are painting a chess board. After 1 coat of primer, you can still see the chess board. That is called "printing through". The layers of primer are not opaque enough to really hide it.

Note that if you are finding solids at the bottom of your primer can, that's because you did not mix the primer enough, and that will get you poor performing primer, since the solids are what makes it opaque! You can always take the can back to the paint store and ask them to shake it on their paint shaker.

The job of the primer is to equalize the underlying surface (in a number of factors, color is one of them). If the underlying surface is not equal, the primer job is not done!

Now I'll tell you a secret: 1-coat paint is a lie. If you try it in 1 coat, the primer color will "print through" somewhat. In other words if you painted a wall half 1-coat and half 2-coat, the difference will be obvious - the 1-coat side will have the primer color printing through somewhat. They're just hoping your application will be even enough that you won't notice lol.

Needless to say if the primer is not layered enough to make the surface totally consistent, that will immediately print through the 1 coat!

So I plan for 2 topcoats and n primer coats, with the value being enough to stop all print-through of the underlying surface. The last primer coat doesn't need total coverage of all differences (e.g. the chess board), but it needs to be close enough that the 2 coats of topcoat will seal the deal. Since I don't like re-doing jobs that failed, to me that means "pretty darn close".