Abstract: The varnish comprises a plasticizing resin, a diluent, a matting compound and an epoxy silane compound, this latter having excellent antireflection characteristics and enabling the varnish also to adhere to smooth glass. At the moment of use, a catalyst is added to the varish, the catalyst being an amino silane compound which causes the epoxy compound to polymerize, so that the varnish layer becomes resistant to abrasion and to chemical agents. The varnish can also be colored with aniline dyes such as aniline green and aniline yellow. On varnishing, the tube is first degreased, then varnished with several layers, and finally baked at a temperature of between 80.degree. and 150.degree. C. for a time sufficient to cause polymerization of the compound.