Ken Collier: Primers are one of the secret weapons of pro-painters and they can help you get great results when you're painting the walls of your house. My name is Ken Collier and I'm the Editor-in-Chief of The Family Handyman Magazine, the leading brand for do-it-yourself homeowners.

In this video, we're going to talk about how you can use primer to cover stains on your walls. Primers can cover just about any stain your walls could have; food stains, smoke, mold and mildew, crayon if the kids are kind of gotten loose on the walls, marker, anything. We're in our studios today and we have a demonstration wall behind me, and we'll make some stains on it to show you just how effective a primer is at covering stains. Let's start off with some marker stains. There! That's pretty dramatic, huh, and we'll put some lipstick on. And now how about some food stains? What would be the worst food stain? Mustard, right. Just to pretend that we've kind of tried to clean that off a little bit, I'll give it a wipe. And finally, I'll do something to mimic the kind of water stains that you frequently have if you've ever had a leak like a plumbing leak or a roof leak, and I'll use some coffee for this. We'll let these stains dry for a couple of hours and then we'll come back and put some primer on.

So it feels like our stain is dry. What I'd like to do is give you a little demonstration by painting over these stains with a plain, white wall paint and also some primer, so you can see the difference that the primer makes. Now for light stains, you can often use a premium latex primer. This you can apply with a nylon or polyester brush, the same kind you'd use for latex paint or a roller and you should clean up with water and soap just the way you would with latex paint. But for heavier stains, especially water stains or smoke damage, you want to use an oil or solvent-based primer. In this case, we're using an odorless primer which is my favorite, but even though, it's odorless, you still want to use cross-ventilation, typically a fan and an open window, so you can get air to move in and out of the room you're painting.

So let's roll on some wall paint first, and here's some oil-based primer. So we've got one coat of paint, one coat of primer, we'll follow that up with a second coat of paint and we'll see how it looks. So our paint is dry. Here we have just flat white paint, here we have primer plus paint. You can see the dramatic difference. With just the paint, the lipstick is showing through, we can see a little bit of mustard stain and that would gradually work itself through the paint as well. And the coffee stain in particular, you can see the streaks here. Water-based stain is also working itself through the paint.

Here the primer has locked in those stains, and one coat of white paint on top of it gives you a perfect painted wall. So I hope this has convinced you that using a primer on your walls is a great tool if you have any kind of stains at all.