What is primer in decoration painting and how do you use it?

In new construction, primer seals the walls and allows the finish paint to adhere. When repainting, primer is used for several reasons. If a wall hasn't been painted in a long time, you will find that fresh paint will soak into the wall unevenly, making the paint look splotchy. Primer serves the same purpose as it does with new construction. If you are changing colors drastically, or painting over a hard to cover color, primer will mute the color and allow the finish paint to cover. If your finish color is light, use the primer as is. If you are going from a light color to a dark color, you can have the primer tinted to help coverage with the finish paint. If you have done any patching on the wall, you have to prime or the repairs will "flash". One big reason to use primer, in addition to its coverage and adhesion properties, is that primer is often cheaper than finish paint. There are different types of primer depending on what you are trying to accomplish. Hope this helps.  more