A process for forming a vitreous layer on a refractory surface, in which a vitrifying
agent is projected by means of an apparatus against the surface with an oxygen-containing
carrier gas and simultaneously with a combustible gas, the latter generating a
combustion flame, characterized in that the vitrifying agent comprises particles
of cullet and in that the flame generated provides, at least partially, the heat
needed to form the vitreous layer on the surface. The vitreous layer thus formed
makes it possible to prevent the build-up, on the refractory walls of high-temperature
ovens, of dust or by-products coming from the raw materials and/or their reaction products.
