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303,359 · Belcher · "Mosaic of Glass and Lead Glazing" · Page 2
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between the same, is pressed a sheet of asbestus or other flexible material, which, having been gummed or covered with an adhesive substance, adheres to said pieces, so that when said sheet is raised, as it subsequently is, and turned over, the glass portions are brought to the top of the sheet without bring changed in their relations to one another. A second sheet similarly gummed is then caused to adhere to the other sides of the glass portions and the parts laid aside to dry, a warm drying-chamber being employed. After this the sheets with the mineral parts between are placed in suitable frames or molds, and tilted up, as shown in Fig. 13, so that the metal can be poured between the edges of the sheets and into the passages between the sheets. Such being done and the passages filled, the metal hardens and forms a frame-work around the glass or mineral parts which holds said parts in fixed relation to one another. I prefer to heat the glass and asbestus sheets to quite a high degree of temperature, so that the metal will not harden or solidify before it has completely filled the passages. I prefer to use as a binding metal one-- such as an alloy of lead, antimony, and bismuth-- that will expand in cooling, and one having a low point of fusion. A preferred composition for this purpose will probably form the subject-matter of a subsequent application. The expansibility of the metal in cooling causes the same to hold the glass portions with great firmness and prevents the looseness and consequent rattle resulting from the use of contractile metal, such as pure lead.
    I do not wish to limit myself to the use of flexible sheets of material or to gummed sheets in the process of casting a frame-work around mineral pieces, as any device adapted to hold the said pieces in fixed position between two surfaces, so that they may be subsequently cast to form a mosaic, embodies the spirit of my invention and may be employed. But I prefer the employment of asbestus in the process, as it cannot be destroyed by contact with molten metal, is porous, and thus allows the exit of air to a certain extent as the passages fill with metal, is pliable and plastic when damp, and thus is easily made to conform to uneven surfaces, and is otherwise peculiarly adapted for the purpose.
    In preparing the sheets having the mineral parts therebetween to receive the metal, I prefer to employ a suitable press-- such, for example, as is illustrated in Fig. 14, Sheet 3. By means of this device the side plates or sheets are brought into perfect contact with the sides of the portions of glass, so that the metal will be more effectually prevented from covering the side surfaces of said glass portions.
    Under certain circumstances it is found desirable that a heavier frame than that lying flush with the side faces of the glass is desirable, and to produce such a frame I form in the side plates or sheets a groove or grooves,
e, Figs. 19, 22, Sheet 3, corresponding with the passages between the glass portions a or some of said passages. By thus doing, a transverse rib or ribs, f, Figs. 7, 12, 21, integral with the cast frame-work is formed, which adds greatly to the stiffness of the mosaic, as will be evident. The grooves may be formed in the sheet material before it is applied to the surface of mineral portions by making corresponding grooves in an appropriate bed, then laying the damp sheet into said grooves, after which the damp material is allowed to dry. After this the said material is gummed and placed in position on the surface of the mineral portions.
    Should I wish to give greater strength to the mosaic than the ribs f afford, I may enlarge the grooves e and arrange therein suitable bars or wires. Around these are cast the binding metal, the wires being inclosed with the softer metal forming cores g, Fig. 13, which add greatly to the tenacity of the frame-work. Under other circumstances it is desirable not only to give firmness or rigidity to the mosaic as a whole by forming the transverse strengthening-ribs, but it is also desirable to give greater security to the individual pieces of glass. To this end I may form the cast frame-work as illustrated by Figs. 25, 26, Sheet 3, in which case the cast frame-work has projecting and overlapping flanges, which overlie the edges of the mineral pieces, holding the same with such firmness as to prevent the same from being easily detached by the force of impact. This result I gain by first securing upon the surface or surfaces of the glass portions sheets of material of a size smaller than the glass or mineral portions, so that when the glass and sheet secured thereon are in position the former will project from the latter, as shown in Fig. 12, the passages thus formed being T or I shaped, and thus adapted to cause the metal to form the overlying flanges.
    It will thus be observed that the strengthening-ribs, broadly considered, may be formed either by grooving the plate d or by building the same up by applying sheets of material, said groove lying therebetween. This building process may be also applied in forming simple strengthening-ribs. The example, the sheets of material illustrated in Figs. 23, 24 may be arranged in the molds, as shown in Figs. 19, 22, to produce the ribs shown in Fig. 21.
    When the asbestus or flexible sheets or plates of material provided with adhesive substance are applied to the portions of glass and the casting process is completed, said sheets may be removed by simply wetting them and dissolving he adhesive substance, after which said sheets may be removed for subsequent use.
    I have found in desirable under some circumstances to form the mosaic hollow or concaved, as exemplified in Figs. 3 and 4, Sheet 1.