what is primer used for

Primer is a base coat used to treat a surface before applying a topcoat, such as paint or makeup. It is formulated to ensure maximum adhesion, which means better paint or makeup adhesion and a longer-lasting finish. Primer can cover imperfections such as areas of a wall that may have been patched or repaired, block and conceal stains, and provide a uniform surface for paint or makeup to stick to. It can also neutralize the color of a surface so that the truest, most brilliant color shines through when new paint or makeup is applied. Primer is necessary for surfaces that are porous and would otherwise absorb the first few coats of paint or makeup. It can also be used as a stain-blocker for walls. However, primer is not always necessary for previously painted surfaces that are in good condition, both interior and exterior, that are not peeling or chipping. In some cases, modern quality exterior and interior paints are self-priming, meaning they are formulated to adhere to most previously painted surfaces without the need for a prime coat.