Зображення сторінки
PDF
ePub

even where the opening is but an inch and a half in diameter; it permits the removal of cores from a design that has under-cutting extending horizontally with the face of the work; these features alone which are possible in no other class of material available for concrete molds, make the wet sand mold process ideal for every class of ornamental concrete work.

The low cost of molds, using simply the cheapest and most common of materials; the ease and rapidity with which work may be produced; the increased density and strength of the concrete; perfect details to the lines of ornamental designs, together with the perfect curing of the work without the least attention, as it remains enclosed by the wet sand until the final set or hardening of the cement has taken place; these facts alone are convincing that this process is not only the one probably first employed in this work, to produce ornamental effects in concrete, but will be the first in efficiency at the present day to enable the concrete worker to mold any design he may desire, without restrictions as to releasing the mold from the finished work.

A. A. HOUGHTON. MAY, 1910.

CONCRETE FROM SAND

MOLDS

CHAPTER I

IGIN

F THE

THE ORIGIN OF THE SAND MOLD PROCESS OF MOLDING CONCRETE AND THE VALUE OF SAME

THERE is a wide difference of opinion among concrete men as to the exact origin of this method of producing “cast stone” or concrete. To all those who have made it a subject of study everything points to the apparent fact that it is but a modern adaptation of one of the arts of the first Roman architects; this is well within reason, for it is an established fact that the Romans employed wood forms in molding concrete work, and, as the many examples of intricate ornamentation appearing upon these works show positively that they could not have been produced with wood molds, and in many examples where there is deep under-cutting, the use of plaster molds would have been impracticable; looking at the matter from this view-point the fact is obvious that our ancient workers turned to the easiest solution of this problem, which would be that the pattern or model of the ornament was modeled in clay; a form of plaster or some easily worked material that was within the possibility of being worked by their crude tools, then an impression or mold of this model formed in sand, or some easily separable material, so that the completed work and mold could be separated without injury to the ornamentation, was made.

Looking at the subject from the point of practicability this is to the thinking student the only logical way in which many of the elaborate ornaments of the Roman architects could be formed, when we consider the tools with which they must work at that period.

This system or art, as it may be termed, has not been revived until within the last few years as a method of producing “cast stone” or concrete, while the knowledge is known to but few

« НазадПродовжити »