Abstract: A coating composition for building materials which comprises 100 parts by weight of a quaternary ammonium silicate having a silica content, calculated as SiO.sub.2, of 5 to 70% by weight, 2 to 200 parts by weight of a metal oxide and/or hydroxide capable of converting silica sol to silica gel and water in an amount sufficient to plasticize said composition.

Abstract: For coating the surfaces of various materials with a paint or like coating liquid, use is made of a spray roll typically having bristles in the form of steel wires or the like implanted in the cylindrical surface of a cylindrical core in dense, radial arrangement. A supply plate which may be of flat, elongated shape is disposed tangentially of the spray roll so as to be in substantial contact therewith at least along one of its longitudinal edges. Hence, by continuously delivering the coating liquid onto the supply plate in the form of a layer of uniform thickness while the spray roll is in rotation in a prescribed direction, the coating liquid can be sprayed onto the work which may be traveling at a constant speed in a direction at right angles to the axis of the spray roll. Several examples of the spray coating apparatus are disclosed on the basis of these fundamental concepts of the invention.