Need of primer :-  Primer is an undercoat that you paint onto the wall before painting it with color. … If you’re changing the color of your wall from very dark to very light, priming it first will make it easier to cover with the lighter color and could save you from applying a second or even third coat of paint.

Paint and primer have two different, distinct functions and many times work best as two separate products. Paint provides color, hiding, sheen, scrub resistance and protection against the elements. … Regular paint and primer in one products would not adhere to slick surfaces without a specialty primer. If you don’t use primer before painting then  it has a glue-like base, drywall primer helps the paint adhere properly. If you skip priming, you risk peeling paint, especially in humid conditions. … You might blame this on the quality of paint you used, but the truth is that failure to use primer caused the problem.  primers dry to the touch within 30 minutes to 1 hour. But do not paint the wall until the primer dries thoroughly, which can take up to 3 hours. High humidity and cool temperatures prolongs drying times. Although paint might initially stick to an unprimed wall, you risk blotchy, cracking, peeling results if you pass on primer. … Generally, one to two coats of primer will suffice for painting interior walls, but how many you’ll need depends on the wall material, the paint color, and the type of primer used. It comes with a flat sheen to promote bonding between the substrate and top coat, which does not hold up as well to sun, rain, and dirt as satin or glossy paints.

Prepare Walls for Interior House Painting

1. Clean the walls: To clean the walls that need to be painted, you can use a vacuum cleaner or a towel. …
2. Remove old paint: To remove cracked or flaking paint, use a paint scraper and sandpaper to smooth the surface.

 Note:-  (a) While there is no best way to clean walls before painting, most walls can be washed using a sponge and warm water. For surfaces that have exposure to oil or grime, like kitchen walls, wash with a solution of water and grease-cutting detergent and follow up with clean water to remove any residual cleaning agent.

(b) 280 gm to 300 gm water add into the 1 litre.