A mixture of loose polymers for dissolving in water; primer obtained after thorough mixing strengthens old and new, porous and absorbent substrates, such as concrete walls, cement-lime and gypsum plasters, plasterboards, cement-wood chip boards. It limits surface water absorption and increases adhesion, thereby reducing paint consumption. This product significantly reduces transport costs, allows storage and transport at negative temperatures and is significantly cheaper than ready-to-use primers.