Assessing the tonal qualities of an acoustic musical instrument is a challenge that has long been pursued by researchers in musical acoustics. This is a topic of particular interest when it comes to discussing the case of violins. Historical violins are often believed to owe a great deal of their celebrated timbral qualities to the choice and the make of their finishings, particularly the ground coat and the varnish. The impact of such finishings on the instrument's tonal qualities, however, is not so well understood. In this paper we investigate the impact of the finishing process on the instrument's timbre through a joint analysis of the characteristics of the materials involved for this process (ground coat and varnish) and audio features extracted from the sound produced by such violins at various stages of their finishing. Some of the results are compared with those found in the literature for validation purposes. The characterization of the impact of ground coat and varnish has been conducted during the finishing process of a new violin.