Abstract: Apparatus for evenly and uniformly depositing particulate suspended in a gas on at least one surface, and in at least one direction, of a substrate. The apparatus has an exit slit (13) and a passage for communication of product including a main conduit (1), a plurality of secondary conduits (2) which are of equal length and internal diameter and a primary slit (6) communicating with a chamber (7). The slits are coextensive in length and the secondary conduits, of equal length, connect along the primary slit at regular spacing so that product is delivered uniformly to said exit slit.

Abstract: The surface of a transparent refractory material such as glass or a vitreous ceramic is coated with a semi-reflective film of tin oxide by projecting finely divided particles of a pyrolytically decomposable organotin compound against the surface of the substrate material that has been heated to a temperature of between about 400.degree. and 650.degree. C. The finely divided organotin compound has a particle size of not greater than about 20 microns and is suspended in an anhydrous carrier gas to which carrier gas has been added a gaseous fluoride compound. In an advantageous embodiment of the process the pyrolytically decomposable organotin compound is dibutyl tin oxide, the carrier gas is dry air and the added fluoride compound is dry hydrogen fluoride.