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Flint glass derives its name from the fact that in England the silica, which is the main constituent of all glass, was procured from flints which were calcined and pulverised. Being highly refractive it is extensively employed in the manufacture of optical instruments-telescopes, microscopes, etc. Quartz and fine sand are now used in the place of flints. The glass is soft, and hence easily scratched and dulled. It is essential that only the purest materials be employed, and special furnaces and pots are needed. Flint glass was known in quite early times. It was probably discovered by accident that certain stones were fusible, for fossil glass is found in many places where great fires have been. Volcanic glass - obsidian - is a wellknown substance, while there exist in Scotland ancient forts, the stones of which have been fused together by the action of heat. The Venetians used quartz in preference to sand, since the latter was liable to contain impurities, and the Venetian craftsmen who settled in England were accustomed to ensure the purity of their silica by calcining flints. Crown is the finest sort of ordinary window glass. Plate glass is the superior kind of thick glass used for mirrors, shop windows, etc. It will be noted that it is the only kind of glass which contains soda.
The process of glass manufacture comprises three stages, mixing, melting, and blowing. The various ingredients are first finely ground and then thoroughly mixed by the aid of a mixer, forming what is known as the " batch." This is placed in melting pots. These are crucibles of fire - clay, i.e. clay capable of withstanding the action of heat. The clay must be of the finest quality, and be carefully freed from extraneous matters which might affect the quality of the glass. Hence the manufacture of the " pots " is itself an industry of some importance, and as each costs some £10, they form an important item in the expense of manufacture, especially as the pots are short-lived, some eight to ten weeks being the average life of one of them.
The ordinary pot is an inverted section of a cone, the apex being closed. For flint glass a covered pot is essential, the form ordinarily adopted being a bell-jar closed at the bottom and with an arched opening at the top. Each pot holds from ten to fifteen cwt. of the "batch." When full, the pots are placed in specially constructed furnaces, holding from five to fifteen pots, and capable of producing a temperature of from 10,000° to 12,000° F. The details of the firing are intricate and interesting but have no direct bearing on our purpose; their object is to produce complete fusion, to allow for the removal of all impurities, and to ensure the homogeneity of the product.
The final stage with which we are concerned is that of blowing, since all table glass, worthy of being called table glass, is blown. In other words, every decanter, vase, tumbler, and wine glass of the better sort begins its existence as a bubble of molten glass at the end of an iron tube-the glass-blower's tube -and owes its form to the delicate touches of simple tools held in a skilful hand and guided by a . trained eye. It is this fact which gives glass its individuality. There is no hard-and-fast rigour of line, no mechanical uniformity of shape, such as is associated with machine-made goods; even the simplest wine glass is an individual thing, which the taste of the craftsman has endowed with artistic distinction whilst retaining its simplicity of form.
It is a matter for regret that the glassblower's art is seriously threatened in these latter days of hurry and competition. The demand for cheap glass has led to the introduction of blowing machines, in which the bubble of molten glass is taken up by one of many blowing tubes, and placed inside a mould, air being driven by machinery through the other end of the tube and inflating the bubble until it touches the sides of its mould. The budding craftsman thus loses the practice of blowing these simpler forms, and as he is now forbidden to work at the furnaces until he is over fourteen, he often fails to acquire that lightness and dexterity of hand which are the mark of the first-rate craftsman, and which can be most readily gained in early life. There is, of course, no reason why common vessels should not be produced in this way, and tumblers, decanters, and lamp glasses are so manufactured in large numbers.
Needless to say, moulded or pressed glass has little value, either intrinsic or artistic, in the collector's eye, unless it has acquired distinction on account of its age; for moulded or pressed glass has been known from early times, and it is of the greater interest, since only English glass, i.e. flint glass, or glass of similar characteristics, can profitably be so dealt with. It will be readily understood that only glass of a low melting point, which does not quickly solidify, and which at the moment of solidification expands and fills out the interstices of the mould, can be successfully treated in this way. One bar to the extensive use of this form of glass was the cost of the essential lead and potash. These are often now replaced by baryta and lime, with the result that a very suitable glass is produced, which contains no appreciable quantity of either lead or potash.
The art of glass-cutting in Europe dates back to the middle of the sixteenth century, when it was extensively practised on the Continent, particularly in Bohemia. The earliest examples were probably imitated from the rock-crystal cups of ancient Greece and Rome. There is no doubt that in both these countries the mentation of some vessels art was practised for the ornamentation of the famous crystallinum, whilst undoubtedly cut out of were the solid block.
The discovery of flint revolutionised the art of glass ornamentation. The strong refractive powers of the new glass made it specially suitable for cutting, which brought out a wonderful fire and sparkle that even the finest art of Bohemia and Venice had not been able to attain. At first, of course, the English craftsmen were far inferior in artistic merit-both as regards design and execution -to those of Bohemia; but the superior brilliancy of the metal atoned to a great extent for the deficiencies of the workmen, and Early English cut wine glasses and punch glasses are by no means to be despised. " L'article Anglais solide et confortable, mais sans elegance," spread the fame and fashion of English glass throughout the Continent and, incidentally, over the world.
The earliest examples of English cut glass are perhaps the thistle-shaped glasses, originally fashioned in Bohemia but adopted by Scotland as representing the national emblem. Apart from these, the ogee-shape was most commonly selected as being more amenable to artistic treatment than the bell.
The stem is usually knopped and cut into facets, and is invariably hexagonal in shape. The cutting is continued beyond the top of the stem on to the lower part of the bowl, so as to give a kind of finish. Sometimes, indeed, the cutting is made to include the bowl in a scheme of decoration, and the rim is engraved with conventional designs, wreaths of flowers, etc. Towards the end of the eighteenth century the facets became long flutes.
The process technically known as glass-cutting is essentially one of grinding and polishing. The grinding is done by a wheel, made of castiron, and made to rotate rapidly by a continuous band passing over a revolving shaft. Above the wheel is a receptacle containing sand and water, which can be fed on to the wheel as desired. Smoothing is done by a sandstone wheel, similarly mounted, and polishing by a wooden one fed with putty powder. The craftsman holds his piece in the hand, pressing it against the rotating wheel.Engraving is really very fine grinding, done usually with a copper wheel or, rather, disk, whilst etching is done by coating the glass with wax, or some similar protective substance, scratching the pattern through the wax and then subjecting the piece to the action of hydrofluoric acid.
It need hardly be said that only the best kinds of glass are cut by a method which makes such demands on the time and skill of the workman; the cheaper kinds of glass are all moulded or "pressed." Pressed glass is also essentially English, no other kind, save flint glass, being suitable for treatment in this way. 1 t is, in the first place, essential to obtain a metal which has a low melting point, and one which does not shrink in solidifying, as that would draw it away from the sides of the mould, and so effectively spoil the design. The low melting point of the metal enables the product to be "fire polished." In this process it is reheated to a point sufficient to melt a thin surface layer, and so remove any roughness due to the process of moulding, and leave a smooth bright surface. The art of pressing glass has been brought to a high degree of perfection, elaborate decorations being produced with ease. The cost of the process, too, has in recent years been lessened by the use of baryta and lime, in the place of lead and potash, and in this way the output has been greatly cheapened, while baryta glass, if inferior in sparkle to lead glass, is yet far more brilliant than ordinary glass.
The problem how to distinguish real old glass from modern imitations is one that besets the collector at every stage of his progress. A few specimens supply their own testimony in the shape of a date, but it is by no means impossible to engrave a date on a piece of specious-looking real antiquity, and so give it a fictitious value, by making it appear "the thing which it is not."
As to the character of the glasses themselves, shape alone is no criterion of age. Apart from the possibility of deliberate imitation, it does not follow that because a piece is ponderous, clumsy in appearance and, to a modern eye, unduly capacious, that it is necessarily an early piece. Right from the beginning of glass manufacture in England, two qualities, at least, were undoubtedly manufactured; the better to ornament the tables of the great, and the poorer for service in kitchen and tavern. Whereas articles of the former were as dainty and artistic as the skill of the craftsman would allow, the latter were roughly made and deliberately ponderous to bear the rougher usage to which they were subjected. As the same practice continues up to the present day, it follows that there is in existence a considerable quantity of common glass with all the attributes, as far as shape and clumsiness of form are concerned, of that of an earlier period.
Possibly the appearance of the metal and the style of workmanship are as reliable guides as tiny others. The metal of the earliest glasses wits by no means perfect. Instead of the beautiful clarity and perfect transparency we are accustomed to associate with glass, there is often a streakiness or cloudiness visible in the material, together with numerous bubbles and flaws. If the striations are horizontal, the glass is of an earlier type than if they are perpendicular. The sides of the bowl are often irregular, and the stems are often clumsy, uneven, badly balanced, and altogether disproportionate in point of size to an eye accustomed to the slenderer style of modern glassware. An im portant point is the junction between the bowl and the stem. For some extraordinary reason, the welding of the two seems to have given the ancient glass-blowers considerable trouble, and the join is often too clearly perceptible. Hence the collector who comes across an apparently ancient piece bearing evident signs of clumsy joining should give it more than casual attention. Sometimes, to obviate the difficulty, the base of the bowl was made into a kind of knop, and at other times the junction was hidden by an irregular band-the prototype of the collar which so often appeared in glasses of a somewhat later period.
The bubble which appears in many stems was probably the outcome of accident and possibly of an attempt to imitate the hollow stems of Venetian glass. It is worthy of note that whilst the bubble is almost invariably present in the baser forms of early eighteenth-century glass, it is frequently absent from the finer varieties. Another point of difference is that the better specimens rarely have the folded foot, which is invariably present in the coarser makes, the turning under of the rim, whilst plastic, to make a kind of welt, being an obvious precaution against the rougher usage to which they were inevitably subjected. Sometimes the feet were domed, but these were difficult to make and the numbers were restricted. In some specimens ridges or ribs are formed on the upper and lower sides of the foot.
The earliest glasses were devoid of any attempt at decorative engraving, and these plain glasses may also be roughly classified by noting whether the glass rests on the flat of the foot or on the rim only. The former are of the earlier type.
Among the tests which the collector might apply are the following:
Note whether the glass rings clear and sweet in tone. In twisted stems, note whether the stem twists to the left or the right. The genuine glasses have almost invariably stems twisted to the left. In opaque-twisted stems, note particularly the colour of the spiral. In the forgeries the opacity is less definite, the twist often having a kind of translucent look.
Genuine old glass often has a cloudy tinge with frequently a tone of steely blue. Forgeries may show a greenish tint.
In old glass the centre of the base, where the piece was, after being finished, knocked off the pontil, is generally left rough; in the imitations it is generally ground smooth.
The foot of a genuine old glass quite flat, there is always a slope-sometimes a very pronounced one-from the centre to the edge. The modern imitation, usually made abroad, often has a perfectly flat foot.
The edge of the bowl in a genuine old glass is always rounded, never left hard and sharp.
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