Fig. 160
162. Figured Rolled Glass.—Glass known generally as figured rolled glass is manufactured for use in offices, public buildings, and private residences where a glass is required to intercept the vision and still diffuse the light. This glass has practically supplanted the varicolored cathedral glass previously used, because of its obscurity without reducing the quantity of light. Figured rolled glass is made in various artistic designs, several of which are illustrated in [Fig. 160], and is ⅛ and ³/₁₆ inch in thickness. This glass is inexpensive; the prices range from 15 to 25 cents per square foot.
163. Plate Glass.—The process of manufacturing plate glass is radically different from that of common sheet glass. The latter is blown, while the former is cast in large sheets and placed in annealing ovens to cool. When taken from the ovens the glass is rough and opaque, but it is afterwards ground and polished to make it transparent, the polishing being the most delicate process in its manufacture. Plate glass glistens like a mirror and reflects like one; objects seen through it are sharp and clean-cut; it has no imperfections or wavy effects, and does not distort and deform objects as does sheet glass.
164. Beveled Plate Glass.—The term beveled plate is applied to plate glass the edges of which are ground and polished to form a bevel, or border, around the glass. Plate glass finished in this manner is much used for glazing entrance doors and for ornamental work. The additional cost for beveling is slight compared with the effect resulting therefrom.
165. Floor and Skylight Glass.—Floor glass is made only from rough rolled or hammered glass in ½-, ¾-, and 1-inch thicknesses. The prices range from 30 cents to $1 per foot, according to the thickness.
Skylight glass is similar to floor glass, but can be procured in ⅛-, ³/₁₆-, ¼-, and ⅜-inch thicknesses, and in either ribbed or roughened surfaces. This glass is inexpensive, the prices ranging from 8 to 15 cents per square foot. Large quantities of skylight glass are used for mills, skylights, and various other purposes, but it is not used as a fire-retardant, as wire glass has entirely superseded it for this purpose.
166. Wire Glass.—Glass with wire embedded therein, as illustrated in [Fig. 161], is made either ribbed, rough-rolled, “maze” design, or clear, polished plate. The wire netting is embedded in its center during the process of manufacture, thus producing a very strong glass that is a good fire-retardant. The temperature at which the wire is embedded in the molten glass insures cohesion between the metallic netting and the glass, and the two materials become as one; thus, if the glass is broken by shock, by intense heat, or from some other cause, it remains practically intact. Wire glass combines the strength of the wire netting and the glass plate, and the wire is so thoroughly covered as to obviate the possibility of rust or corrosion. This glass possesses extraordinary strength; a piece ¼ inch thick is as strong as ordinary glass of twice that thickness. When wire glass is broken, it will not scatter like plate or skylight glass; consequently, it finds extensive use for overhead work, where falling glass due to accidental breakage would be a source of danger.
Fig. 161
Wire glass is made ¼, ⅜, and ½ inch thick, and up to 40 inches wide and 100 inches long. This glass is sold at from 30 to 40 cents per square foot for rough, ribbed, or maze pattern, according to the thickness, while polished wire glass costs either 60 cents, 95 cents, or $1.25 per square foot, according to the dimension of the light. Wire glass is practically burglar-proof and missile-proof, and when set in approved metallic frames forms a most efficient fire-retardant window. In its use as a fire-stop, it possesses advantage in that it does not hide the incipient blaze like steel-plate or tin-lined shutters. Windows glazed with wire glass require no shutters for protection, but an opening may be made in it by a blow from a fire-ax. Wire glass as a fire-retardant is approved by the various boards of fire underwriters, and it may be used for windows, skylights, and other exterior openings exposed to fire hazard.