PREFACE The writer has endeavored to treat the subject of molding concrete bath tubs in a complete manner, employing only such molds as are certain of success, as well as having the advantage of being easily and simply constructed. The close imitation of the usual type of marble, metal or composition tub is not essential, even if it is desirable, as concrete is an entirely different material, demanding more massive lines to be durable; hence, other than upon the point of use, the concrete bath tub should be molded and sold as concrete, and upon its merits as concrete, and not as an imitation of any other material. This, of course, should not be construed to mean that the molding of smooth, glossy concrete that will reflect light, like polished stone, in any manner detracts from the beauty of the material, nor can this be judged to be an imitation of stone, as this is but an artificial finish to any product, and is as permissible for concrete as for any other material. The simple construction of the molds for this work, as are fully illustrated in this volume, will convince the reader that the molding of concrete bath tubs is extremely practical, and that there should be a most excellent sale for the finished product in competition with the marble and metal tubs for this purpose, as a concrete bath tub may be molded and sold at a price far less than of other material, and yet yield the worker a good profit for his work. Concrete may also be made an ideal material for aquariums, as it is for natatoriums. The simple and easy method of molding the work with glass inserted into the sides, will be of interest to those who have contemplated any work of this kind. Concrete laundry trays or tubs are extremely practical, and at the low cost of same, with the simplicity and ease of molding, should make them a profitable side line for every concrete plant. The subject of water-proofing concrete is one of great interest, while the writer does not believe that the most positive and successful method for all classes of work has yet been discovered, yet a description of the best known methods and materials in use to-day may be of use and value to the reader who wants to make the best choice for the type of work under construction. April, 1911. A. A. HOUGHTON. Molding Concrete Bath Tubs, Aquariums and Natatoriums The concrete bath tub, as well as any article molded in concrete and intended to retain water, should be of such a mixture as to secure the maximum density of the concrete. This is an aid in making the work water-proof, as the closing of the pores is accomplished, thus demanding less treatment to make a thoroughly water-proof product. To secure the maximum density, without pressure, the concrete must be of a wet mix, so that it can be poured and thus flow to every part of the mold. This permits the molds to have a smaller opening for placing the concrete than if the mixture was to be tamped into the molds. The addition of from one-tenth and one-fourth to equal parts of hydrated lime, in proportion to the cement used, is also of value, as the extreme fineness of the lime causes it to fill the voids or pores in the concrete, thus increasing the density of the work. With a rich mixture of concrete and the addition of lime, usually about 25% of the weight of the cement, work may be molded by the wet process that is practically water-proof; at the worst demanding but the minimum of spe |