Some ornamental processes during manufacture are:- (1) Upon the surface of a vessel in course of manufacture, small drops or seals of molten coloured glass may be fixed, and may be pressed by moulds into the form of stars, gems, etc. (2) A small quantity of molten glass is gathered upon the end of a working - rod, and allowed to lengthen by the force of gravity; the free end is attached to some point on the body of a vessel in course of manufacture, and the vessel is rapidly rotated; thus a thread is evenly coiled around the vessel. A machine is now being used for causing the - vessel attached to the blow - pipe to revolve more evenly and rapidly than can be effected by the unaided skill of the workman. (3) If, after the first gathering, the bulb of white glass be dipped into a crucible containing coloured glass, a vessel may be formed with a coloured casing. In preparing coloured glasses for casing, great care must be taken that they shall neither be harder nor softer than the white metal, or the vessel formed is sure to crack. (4) If a bulb of molten glass be rolled upon variously coloured powdered glasses, flakes of mica, or leaves of gold, silver, or platinum, it will adhere to them, and, by continuous rolling, will amalgamate with them.

Very beautiful effects of colour may be obtained in vessels made from glass prepared as described. (5) Iridescence, which is due to inequality of surface, may be produced by the action of an acid, or of the fumes of chloride of tin, upon the surface of glass. The glass, whilst hot, is subjected to the fumes of chloride of tin during manufacture. Any acid process must take place after the glass is annealed and cold. To effect iridescence, weak solutions of hydrofluoric or hydrochloric acids may be used. In the latter case, the process takes place in heated air - tight vessels. (6) Glass vessels may be frosted by plunging them, whilst still red - hot, into cold water, and afterwards reheating them. (7) Etchings in gold - leaf may be introduced into the substance of a vessel in the following manner:- The gold - leaf is floated on to a thin plate of glass, and etched. The plate of glass is heated, and a mass of molten glass is dropped upon the surface of the gold - leaf, and adheres to the thin plate of glass through the pores in the gold.

The molten mass may be fashioned in the glass - house, or by the cutter. (Powell.) If glass be left in a strong alkaline solution for some months, the surface becomes so eroded that it gives by reflected light the colours of the spectrum in the most brilliant manner. This effect can be produced by ruling very fine lines upon glass plates, but those who have the patience to wait for 3 or 4 months while the glass is in its bath will be highly pleased with the result, and there is no patent on the process, because it is the outcome of an attempt to explain the iridescence found on articles of glass which have been buried for many centuries in moist earth. As to the solution, strong hyposulphite of soda will do, but probably the effects might be more rapidly produced by means of caustic potash or soda; but inferentially any strongly alkaline solution will answer. The common kinds of glass are more readily attacked than the hard varieties; but for ornamenting the ordinary blown water bottles and cast tumblers, basins, and jugs, no process can equal the iridescent.

The only drawback is the time. (Mayer.)

Bay's Process for making the new kind of Glass which is smooth on one side and rough on the other (Craqueti Indien.) - The roughened surface of the glass looks as if it was covered with cracks, and this appearance is obtained by spreading over the surface of a plate of glass a thick layer of some flux or easily fusible glass that has been made fluid or pasty and mixed with coarser' pieces. The glass is then put in a muffle or an open furnace and strongly heated. As soon as this flux is melted, and the glass itself becomes red - hot, it is taken out of the furnace and rapidly cooled. This flux or fused glass then cracks off from the other glass which was attacked by it, leaving numerous depressions in the latter, resembling scales and irregular crystalline forms, crossing and intersecting each other, and producing very beautiful effects when the light falls upon it. This fusible layer is cooled as rapidly as possible, either by a current of cold air or by carefully sprinkling with cold water. If some portions of the glass are protected from the action of the flux, the surface remains smooth there, in striking contrast to the crackled portion. This can be utilized in making arabesque letters, and other designs on a white or coloured ground.

A similar crackled glass is made in another way, by strewing a coarsely - grained flux on a cylinder of glass while still red - hot, and then putting it back in the heating furnace until the flux melts. It is then rapidly cooled, either by sprinkling water on it or waving it back and forth. The layer of melted flux then cracks off and exposes the surface of the glass which has been borroded by it. The cylinder is then cut and spread out in the usual manner.

Penrath has examined a "muslin" glass from Pivout, Charleroi. The enamel was very regular and homogeneous, and the surface could be readily cleaned; weak acids had no action on the enamel; concentrated nitric acid produced no change in 3 days; sulphide of ammonium, however, gave a greyish tint, whilst liquid hydrofluoric acid showed that the enamel was only incorporated on the surface of the glass. The substance giving the "matt" was very fine and delicate, and of a white tint, with a brownish - yellow shade; dilute acids dissolved out lead oxide and boric acid; hot water had no action on it. Its composition was -

which represents a mixture of the following ingredients: -

(Ding. Pol. Jl.)

Three processes connected with the ornamentation of glass, porcelain, and earthenware, were lately brought before the Soctete d'Encouragement, Paris. Cacault, of Colombes, prints, on the fine and hard earthenware of Breil, photographic impressions, which are fixed at a single burning. Lacroix, Paris, has produced pencils like those of graphite, but consisting of various vitrifiable colours. A design executed with them on glass, having the surface slightly dulled, stands the fire, and becomes fixed, like a painting on glass. A similar process, tried on porcelain a few years ago, is said not to have been successful. Lutz - Knechtle, a Swiss, decorates glass, cold, by his composition, made of a solution of silicate of soda or potassium, with the addition of zinc - white or ultramarine. The colours are applied by means of a stamp or roller, dry quickly, and stand washing. The surface of the glass is first finely ground, and any design is then painted on it with a mixture of anhydrous boracic acid, gum, and water. When dry, it is exposed to a temperature at which the boracic acid fuses, and imparts to those portions of the glass the usual lustre, and thus fixes the drawing.