This question is difficult to answer without knowing exactly which painting we’re talking about. But several of Munch’s paintings have been varnished since they entered the collection, and the varnishing has probably been done by a conservator. Varnish is a transparent liquid made of natural or synthetic resin. Often it is applied to paintings both to bring out the colours and to protect the surface. Depending on the type of varnish that is used, paintings may look quite shiny (or more matte).

Kind regards from Vilde, paintings conservator