Skim coat plaster is a thin-layer levelling compound based on gypsum, lime or synthetic resin, applied with a steel spatula or smoothing trowel. It fills small cracks, pores and surface irregularities, creating a clean, homogeneous base for subsequent coatings. Once dry, the layer is usually lightly sanded to achieve maximum smoothness. In interior applications, skim coat plaster is commonly used on plasterboard, concrete walls and rendered surfaces. Layer thickness typically ranges from 0.5 to 3 mm; multiple coats are applied for larger imperfections. Thorough priming of the substrate before skimming is essential for adhesion and a crack-free result.