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Glass & Glass-Making
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Gravure 5 Back

 
AN important change in the making of glass was introduced in England late in the seventeenth century. This consisted of using large quantities of lead with a proportion of potash as a base. The glass thus made is known in England as Flint Glass and in France as Cristal. But it must be remembered that eighteenth-century
"crystal" had nothing to do with the cristallo of Venice, which was a soda glass.
    The use of lead in glass-making was not precisely a discovery; for clear glass of the Roman period has occasionally been met with, and ancient opaque red glass contains lead. The glass of the Middle Ages called "Jewish Glass" also had lead in its composition; but these do not seem to have contained potash.
    Monsieur Peligot, a noted authority, came to the conclusion that "to the English should be attributed the honor of having created in their flint glass a new product, which, by the progress made in the quality and selection of the materials used in its fabrication, has become, without dispute, the most beautiful glassy substance that we know."
    The famous English flint glass was made by mixing three parts of pure sand, well washed and burned, with two parts of red lead and one part of carbonate of potash (usually pearl ash imported from Canada or Russia).
    A small portion of saltpeter and a little oxide of manganese were subsequently added to cleanse the "metal." In fusing this glass, great importance was attached to the quick melting of the materials and to the subsequent rapid working of the pot.
    This glass became very important in the days of William and Mary. The great merit of lead glass lies in its absolute transparency and brilliancy, combined with a certain darkness in the shadows. It has one quality that distinguishes it from all other kinds of glass-- the power of dispersing the rays of white light.
    The elements of which their light is composed are bent aside in different degrees, as they pass through lead glass, so that the issuing ray is broken up into its component colors. This is what gives the fire that is fully brought out when the surface is cut up into facets and angles. Lead glass, or flint glass, in its dispersive power thus stands apart from other glass and rivals the flashing diamond in scattering component parts of light.
    Though English flint glass began to be popular in 1670, it was not until a hundred years later that there was a rage for faceted glass. Everything then bristled with sharp points, pyramids and tiny peaks that exhibited the fire and sparkle of the glass.
    English "cut" reached perfection in 1780. It went all over Europe, and was imported in immense quantities to America. It completely superceded the Bohemian Glass, as the Bohemian had superceded the Murano.
    Glass decorated in the Bohemian and Dutch styles with engraving now held a subordinate position to the famous "cut glass," and so did the beautiful opaque glass decorated with enamel colors, that was made in Bristol about this time.
    Drinking glasses are, perhaps, the most typical forms. Their bowls are straight-sided, waisted or bell-shaped. The design often has a rose on one side and a butterfly on the other. Bunches of grapes and leaves (and a humming-bird sometimes added) were used for wine-glasses; ears of barley were used for beer glasses.
    Towards the middle of the century glass, like pottery, was decorated with political and popular mottoes, designs, portraits and emblems. Stems were "drawn," i.e., formed of the same piece of "metal" as the bowl; or they were made separately and applied to the shank. The drawn stem is often marked by spiral lines in relief, "rib-twisted," cut into flat facets, or with spiral lines within the cylinder. These lines are formed of strings of opaque white, or more rarely, colored glass; or, again, they are made by empty threads formed by drawing out a bubble of air. These are called "opaque twisted stems." The air-drawn stem was brought to perfection in England.
    "We must seek the origin of this device," writes an authority, "in the large 'blows,' often of very irregular shape, that fill the knob, or bulb, in the stems of earlier glasses. This 'blow' is sometimes prolonged into a sort of tail, which passes down nearly to the foot. In other cases we find several small 'tears' in the same bulb formed, it appears, by puncturing, while it is still soft, the little mass of glass destined to form the bulb, and then covering it with a second gathering. It may be mentioned, in a general way, that a loose, widely-spaced spiral is characteristic of the earlier glasses, while the tightly twisted stems are only found in late examples.
    "This applies also to the spirals on the rib-twisted stems of plain glass. There is another point that should not be overlooked. This is that the twist on the eighteenth-century glass always descends from right to left, while on modern imitations the reverse direction is generally taken."