CHAPTER II THE PRINCIPLE OF THE PROCESS. MIXING AND PREPARING THE SAND FOR PLAIN SAND MOLDS. VARIOUS WAYS OF MIXING WHEN making a mold from sand, that requires moving, as is the case with those for small work, the sand must be enclosed or retained in a box form; which is best made in the shape employed by the metal molder in constructing his "flask" or form for holding the sand of mold, with the exception of several points in which the two lines of work differ. The "flask" is a box-like form in two sections without top or bottom; these are provided by building flat board forms just a trifle larger than the box-like form or flask, and which are placed upon the top of same to act as a cover, when it is desired to turn over or move the flask. These cover boards should be built strongly so they will not warp, by placing cleats across same to brace rigidly. The two sections of flask are provided with a "lock" or dowels, the same as those for metal molding, as it is necessary that the two sections may be taken apart and then be placed together in the identical manner as they were before being separated; to do this some guide must be arranged and this is the most simple and positive that can be used. The lower section of the flask is termed in the metal molders' parlance a "drag," and the upper section a "cope," which may be a convenience to the student in classing the different parts of the flask for a sand mold. A departure from the metal workers' flask is the iron rods arranged upon two cleats on opposite sides of the flask; in both upper and lower sections of the flask or form. These rods should fit tightly so that they will aid in supporting the sand when the cope or upper section of flask is lifted; the cleats are arranged in the manner shown at (c) in Fig. 1, so they will not interfere with the model and yet place the supporting strength for sand where the most needed. In Fig. 1 the drag or lower section is shown at (a); the cope or upper section at (b); the strips that lock the two sections together, at the proper point, are shown at (d) and (e), while the cover boards or bottom and tops to the flask are not shown; these are always separate and never fastened to the flask in any manner. At (f) is shown a beveled strip that is placed around the inside of both sections of flask, this must be at the point the two sections are to be divided when the mold is complete, and is for the purpose of supporting the sand as well as making the division or "parting" of the mold much easier and exact; this strip may be used at both top and bottom of each section if any trouble is experienced in lifting the mold and having the sand hold securely. This style of flask is employed where the pattern permits the mold to be in two sections; where it requires four sections a different style is used and in event of simple bas-relief or raised ornamentation, one section of flask is all that is demanded; as will be explained in a later chapter. As the reader will understand the pattern is placed upon one of the cover boards, if in halves or for bas-relief work, and the sand tamped down upon same; the sand is rammed as tightly as possible with the hand tool used, and then a cover board placed over same when this section is filled to top; it is then a simple matter to turn the mold or flask over and the pattern is then upon the top ready to be removed; this is all that is required in molding work where only a portion of the ornament projects from the block as with a bas-relief design, for a box form may be erected around this design, as a mold for the body of the block, and the concrete poured into same, employing the sand mold simply as a face plate. Where the work must be ornamented upon all sides, as a baluster or pedestal, etc., the cope or upper section of the flask is used and a second section of mold made, which will be explained in detail in a later chapter. These general explanations will show that |