Prior to the 17th century, Bhutanese mural paintings were generally executed directly on plaster using ground mineral pigments and binders. Like thangka paintings, murals are created by first sketching out the proper iconometric proportions and the associated color notations. Artists then apply successive layers of pigment until the desired composition takes form. Later, murals were no longer painted directly on the surface but rather on cotton ground which was then affixed to the wall surface.