Priming is mainly intended to ensure that the paint applied over it adheres well and becomes even. Priming also gives an even surface (at least with white, black or self-coloured gesso) and even absorption. When unprimed material with strong absorption is used, thin layers can look dull or blead though (e.g. canvas). With thick acrylic paint layers the gesso has less obvious influence, but as mentioned at the beginning the primer can also ensure that the paint binds better with its surface, especially on smoother grounds.