The base coat, often referred to as the "base coat", is the first layer that is applied to a clean and degreased nail before the colour polish is applied. Its primary function is to create a protective barrier between the natural nail and the pigments contained in the colour polish. This prevents yellowing or discolouration of the nail bed, which can be caused especially by deep and dark shades. At the same time, it smooths the nail surface, fills in small irregularities and grooves, creating a smooth base for even application of the colour layer. Another of its properties is to improve the adhesion of the colour polish to the nail, which prolongs the overall durability of the manicure and reduces flaking. In addition, some base coats can be enriched with nourishing substances such as vitamins or calcium, which help to strengthen and improve the condition of the nails.