Priming is the first treatment applied to an untreated or highly absorbent surface before the actual paint layer. A new or freshly plastered wall absorbs paint quickly and unevenly, which leads to streaking and an uneven colour result. The primer reduces this absorption and ensures that the finishing coat adheres and covers evenly. On walls with damp patches or stains, an isolating primer is applied to prevent these from bleeding through the new paint layer.