Page:The American Cyclopædia (1879) Volume VIII.djvu/31

 attached a punty to the opposite end, the two men separate from each other as quickly as possible, thus elongating the glass into a tube. The globe immediately contracts across the centre, which, being drawn out to the size of the tube desired, cools, so that the hotter and softer portions next yield in their dimensions, and so on until a tube of 100 ft. or more hangs between the men. It is kept constantly ro- tating in the hands, and is straightened as it cools and sets by placing it on the ground. It is cut into suitable lengths while hot by taking hold of it with cold tongs. The diameter of the bore retains its proportion to the thickness of the glass ; hence thin tubes must be drawn from globes blown to large size, or from small ones containing very little metal. In producing canes the glass is drawn out without being blown. Tubes thus drawn out from colored glass are converted into beads by other curious processes. This branch of the manufacture is extensively practised at Murano. The tubes are drawn out 150 ft. in length, and to the diameter of a goose quill, those for the smallest beads by the workmen receding from each other at a pretty rapid trot. The tubes are cut into lengths of about 27 in. and assorted for size and color. Women or boys then take sev- eral together in the left hand, and run them on the face of an anvil up to a certain measure, and with a blunt steel edge break off the ends all of the same length, which is commonly about twice the diameter of the tubes ; the bits fall into a box. These are next worked about in a moistened mixture of wood ashes and sand, with which the cylindrical pieces become filled ; and they are then introduced with more sand into a hollow cylindrical vessel, which is placed in a furnace and made to revolve. The glass softens, but the paste within the bits prevents their sides from being compressed; they be- come spherical, and their edges are smoothed and polished by the friction. When taken from the fire and cleaned from the sand, they are ready to be put up for the market. The Vene- GLASS FIG. 16. Manufacture of Filigree Glass. tian filigree glass, which consists of spirally twisted white and colored enamel glasses cased in transparent glass, is much used for the stems of wine glasses, goblets, &c. ; and when ar- ranged side by side in alternate colors, it is manufactured into tazzas, vases, and other ornamental articles. In making this kind of glass, pieces of plain, colored, or opaque white cane, of uniform length, are arranged on end, the different colors alternating, around the in- terior of a cylindrical mould. The selection and the arrangement of colors depend upon the taste of the manufacturer. The mould and the pieces having been subjected to a moder- ate heat, a solid ball of transparent flint glass, attached to the end of a blowpipe or punty, is placed within the mould, the various canes forming an external coating to the glass, to which they become welded. The ball is now taken from the mould, reheated, and marvered till the adhering canes are rolled into one uni- form mass. This being covered with a gath- ering of clear glass, the lump thus formed, with the ornamental work in the interior, may be drawn into canes of any size and presenting either the natural or the spiral arrangement ; the latter being effected by the workmen rotating the glass in opposite directions while drawing it out into a cane. By variously arranging the colors in this process, and by skilful manip- ulations, many wonderful and ingenious effects are produced. Beautiful vases are also made by the above process, the glass when prepared being blown into that form instead of being drawn into canes. The mille-Jiori consists of a variety of ends of variously colored tubes, cut in the form of lozenges, which, having been arranged to represent flowers or other orna- mental design, are enveloped and massed to- gether with transparent glass. The lump is then worked into the required form, a very common one being hemispherical for use as paper weights. Portraits and even watches and barometers have been represented in the interior of glass ; but in this case these articles and the glass have not formed a homogeneous mass, the former being arranged in a cavity of the latter. Mosaic glass is produced by ar- ranging vertically side by side threads or small canes of variously colored opa"que or trans- parent glass, of uniform lengths, so that the ends shall form a ground representing flow- ers, arabesques, or any mosaic design. This mass is now submitted to a heat sufficient to fuse the whole, all the sides at the same time being pressed together so as to exclude the air from the interstices of the threads. The result is a homogeneous solid cane or cylinder, which, being cut at right angles or laterally, yields a number of layers or copies of the same uniform design. This process was practised with great skill by the ancients, who are sup- posed to have produced pictures in this way ; but in existing specimens, the pieces have been so accurately united by intense heat or other- wise, that the junctures cannot even be dis- covered by a powerful magnifying glass. Vitro di trino represents fine lace work with inter- secting lines of white enamel or transparent glass, forming a series of diamond-shaped sec- tions, each containing an air bubble of uniform size. In making this, a lump of glass is blown