Primer grips to any surface and makes a more uniform bond for the paint. In practical terms, of you want to paint your kitchen, for example, you might not realize it, but close to the stove the wall is coated in years of grease and sauce splatter. This grease will eventually show through your paint, the paint might bubble or flake off as well, so if you Prime the walls to a uniform coating, the paint will sit on top of the primer and result in a longer lasting result. Speaking from experience, I’m just a dad who learns the hard way.
Say you making a sandwich but you want ingredients to stick, you’ll use say margarine/butter on bread right? Won’t be perfect but it will stay.
Now make sandwich without margarine/butter ingredients will likely fall off as you try and eat.
Same applies to primer and paint, say you paint a car bumper raw just paint eventually it will flake, but if you put on primer it will stick to bumper that will allow paint to stick to primer.
Primer is really good at sticking to things. It’s better than sticking to things than paint is. The best part about that, is that primer itself is pretty sticky too, like double sided tape. So when you put the paint on the primer, it’s pretty well stuck.
Also, sometimes you want to paint something, but it might already be one color. When you pick out a paint color at the store, it’s only really that color when you paint over the same kind of background color, and the closer you can keep that background color, the better. That’a where primer comes in: it’s all one color, you can easily see the areas that you might need a little more of it to make them all the same, and if you let it all dry, it makes your paint look the way it’s supposed to.
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