Do you have to apply primer before painting a wall?

I have a room that I'd like to paint. The original paints is pink semi gloss. I'd like to paint the walls using lavender semi gloss. Do I need to apply primer over the original paint first? Do I need to do any sanding?Do you have to apply primer before painting a wall?
You do not need to prime. You just need to ensure the walls are clean and if there are any holes that need to be filled then do it before you paint...(fix anything and lightly sand repairs smooth).Do you have to apply primer before painting a wall?
You don't necessarily need to prime if the existing pain is a very light shade of pink but you do need to do a light sanding and then wipe or vac the sanding dust off the walls., but priming will give a better finish.


If the pink is dark, definitely prime first.


Priming first always gives a better finish coat.


Don't forget to prep the walls first, patch and sand all holes/dents. Then prime the spots or the entire walls.


Then apply finish coat.
Just clean the walls using TSP. No sanding involved. Let walls dry 30 minutes and start painting. You'll be fine. You can get a gallon of water-based kilz-it primer tinted to your paint color to maybe avoid having to do 2 coats of lavender but I doubt it.


I use a paint pad and small sponge roller for painting. Takes less paint, pressure and doesn't splatter like the big rollers do. If I can't finish then I place the rollers and pad in plastic zip-lock bags in the fridge and continue painting the next day.
Gloss and semigloss paints don't want to hold onto the paint when you're applying it so it's best to use a primer. If you don't you'll more than likely need to use two coats of your lavender paint - so you decide which is the easiest and cheapest for you, that will give you the best results. Keep in mind if you're very careful in applying the paint you might get away with only one coat of lavender...
yes you always need to prime over and gloss paint, semi or full gloss. aalso make sure you use a stain block primer like kilz but i prefer zinsser Bulls Eye 1-2s.


the reason is


A paint will not stick well to and gloss surface.


B when you change colors the first color can bleed through- the exception is that a dark color will cover a lighter but a lighter will not cover a darker