"Prepared mineral paints of good grade may be obtained at a moderate price at any modern paint shop. They are, therefore, within the reach of anyone who desires to use them for protecting shingled structures. If made by a reputable manufacturer, the purchaser may be sure that they are prepared from properly selected mineral pigments, carefully mixed with oil, and finely ground, through rapidly revolving stone and steel mills, to a smooth condition. For coating shingles by dipping, such paints could be furnished in a thinner condition than for brushing. It is the writer's belief, however, that better results will be obtained if a heavy coat of paint is brushed upon the shingles, as in this case a greater amount of paint will become embedded within the surface of the wood, and the dried coating will contain a greater percentage of fire-resisting mineral.
Value of Impregnation Process "It is obvious that the application of brush coats of any of the above named salts to wooden shingles would not result in the formation of weather-resisting surfaces.
It is the writer's belief, however, that a shingle manufacturer can at moderate cost impregnate shingles with certain mineral salts which will make them more resistant to fire. Wooden beams and railroad ties are often rendered more durable by treatment with preservatives possessed of fungicidal properties, such, for instance, as creosote or zinc chloride. These chemical substances are forced deeply into the wood by special processes. It would, in the writer's opinion, be practicable for the shingle manufacturer to adopt a similar process for mineralizing shingles. Mineral salts having a high resistance to fire could be used for the impregnation base. Shingles thus mineralized could be rendered still more resistant to fire by subsequently applying a coat of mineral paint. The writer has experimented with various salts for this purpose, and has treated shingles with'their solutions, both by brushing and by dipping.
"Shingles thus treated have shown much greater resistance to fire. The best results were obtained by mineralizing the shingles and subsequently coating them with mineral paint. The mineralizing process of making the wooden shingle thoroughly safe as a roofing material should be carried out in two steps. The shingle manufacturer should undertake the first process of treating the shingle with fire-resisting salts. If shingles thus impregnated are furnished the builder, it is quite certain that he will carry out the second and most important part of the process, which consists in applying a decorative and waterproof coating of fire-resistant mineral paint. It will, of course, be possible to use the old-style creosote shingle stain over the mineralized shingle, in place of a mineral paint. However, the mineral paint will give much more satisfaction, as it forms a durable, waterproof film which is more resistant to fire than an ordinary stain." Mr. Gardner outlines in detail methods for making and testing fire-retardant paints, and concludes the discussion with these statements: "The shingled roof is highly desirable on account of its durability, light weight, low cost, and non-conducting properties.
"Shingled roofs are subject to conflagration when they become dry. Hot cinders from chimneys or glowing sparks carried by the wind from nearby fires, are common causes of roof fires.
"The use of high-grade mineral paints upon shingled roofs eliminates such fire danger. Shingled structures of all types, when properly painted, are not only fireresistant, but they are moisture-proof and highly ornamental.
"The painted shingle dwelling constitutes one of the most desirable types of modern suburban homes."