Page:Popular Science Monthly Volume 29.djvu/363

Rh glasses, etc. Another brilliant effect is produced when a still hot bulb of glass is rolled in finely pulverized aventurine glass, and after this is melted, and previous to the shaping of the vessel, is overlaid with a coating of either colored or colorless glass. A still finer effect is obtained with mica-brocade. The mineral mica, which has deceived so many persons by its golden or silvery glitter, besides being applied as a substitute for metallic bronze dusts, can be colored by the aniline dyes in all manner of colors and shapes. The coarse powder called brocade is used in glass-work, and the color-effect is produced by overlaying it with colored glass. A bulb is blown, for example, out of clear blue glass, is rolled in the brocade, which readily adheres to it, and is then overlaid with yellow glass. The brocade will appear, when looked at from within, of a steel color; from without, of the color of gold. Every flake will reflect the light, colored according as it is looked at.

A recent kind of decoration is shown in those glasses which appear to be held together by a network of gold-thread. This is made by preparing a skeleton of brass wire, and then introducing the glass and blowing it till its mass, having penetrated the interstices of the network, spreads over it and tightly incloses it. The full effect is then brought out by a subsequent etching away of the metal, and galvanic gilding or silvering. Other metal ornaments, insertions, buttons, drops, or figurini are often combined with this. They are cast in steel-engraved forms of type-metal, which reproduce the finest details, and are then galvanically coppered, silvered, or gilded. Another pretty effect is obtained from the clouding which glasses mixed with bone-ashes exhibit on being heated. If a bulb of this kind of glass is blown into a metallic form which is dotted with projecting points, a quick cooling ensues at these places, which leaves its mark after the reheating and finishing in the shape of a regularly distributed clouding.

Only a little need be said, and that of the most modern operations, of finishing, of the grinding, tarnishing, and polishing, ornamentation with gold-leaf and platinum-foil, luster, and enamel coloring, etc. One of the most noteworthy of these operations is that of tarnishing by the centrifugal sand-blast. The objects to be treated by this process are fastened upon revolving wooden pegs in the walls of a wooden box; the sand is introduced into the middle of the box, and is thrown by rapidly rotating fans against its sides and against the glass figures. After it has done its work upon the figures it falls upon the funnel-shaped floor, to flow away and be lifted up again.

A charming effect is produced at the Neuwelt houses by means of a guillocheeing machine in which an engraver's tool is drawn in regularly massed lines over the slowly revolving vase. The vessel has been