478

MANUFACTURES.

Mode ofmakingglass drink*

Manufac- in comparison with the other kinds, it is most commonlytureB - employed for all the ornarnenal utensils which adornthe tables of the wealthy, for which purposes it pos-sesses an additional advantageous property, i. e, of pos-sessing when at the working heat a degree of tenacityand ductility not to be found in any substance in nature.

Although the shapes given to glass vessels are so veryvaried and numerous, they are produced by a fewsimple instruments ; and almost every article, of what-ever figure it may be, is shaped out of a hollow globeformed by blowing.

Glass-blow- (694.) The most useful implement in this process isin S- an iron tube, about four or five feet long. To form a

globe this tube is dipped into the pot containing theglass at the working heat, and turned about until asufficient quantity adheres to it for the purpose intended.It is then held near the ground, by which the glasslengthens by its own weight, and assumes the shape of apear. The workman then blows strongly through thetube, and his breath penetrating the centre of the redhot mass extends it into a hollow globe of uniform thick-ness. It must be blown out as large as intended, andthe force of the breath kept upon it for a few seconds,till it stiffens by cooling, otherwise it would sink againby the pressure of the external air. This operationproduces a hollow globe, adhering to the neck of theiron rod, out of which an immense variety of forms maybe produced.

We cannot here pretend to give an adequate idea ofthe ease and dexterity with which this beautiful substancefrig utensils, is formed from a globe into the numerous shapes givento decanters, wine-glasses, &c. The following descrip-tion of the mode of making the common tumbler, whichis perhaps the most simple table utensil, will howeverillustrate in some measure the manner in which themanufacture is conducted.

A hollow globe with a short neck being first blownon the iron rod, as above mentioned, it is transferredto a short solid iron rod by an assistant, who dips theend of the rod into a glass pot, and brings it out with alittle melted glass adhering to it, which he immediatelyplaces at the bottom of the globe at the part directlyopposite the neck: to this it firmly unites, so that theglobe becomes cemented on this second rod, by meansof the melted glass. The workman then wets a smallpiece of iron with his mouth, and lays it on the neck ofthe globe, which is still extremely hot, and thus causesit to crack all round in a second or two, so that with aslight pull it comes off, leaving the globe open at theneck, and attached to the second rod on the oppositeside. The globe is now again softened by holding it fora few seconds over the mouth of the glass pot, and aportion of it is cut from the open end by a pair of shears,leaving the remainder in the form of a cup. The work-man when at work usually sits upon a kind of arm-chair, the arms of which slope forwards, and are coveredwith a flat, smooth, iron plate; so that by resting therod on both arms of his seat, and twisting it backwardsand forwards, the hot glass at the end is made to revolvelike clay in a potter’s lathe. The workman takes in hisright hand an iron instrument, in some measure resem-bling a pair of sugar-tongs, being connected at top bya flat elastic spring, but having the prong nearly of around figure. By this simple instrument he may-give the glass while in motion an infinite numberof shapes with a degree of facility that can scarcely beconceived by a person who has not witnessed the opera-

tion. If the glass have cooled below the working heat, Mech»n' calprevious to the final shape and smoothing being com- f* roce SSi;> )pleted, it must be again heated by holding it at themouth of the crucible, and continuing the operation;if not completed by the second heating, it must bere-heated, and so on alternately until the vessel is ofthe required shape, when it is separated from the ironrod by wetting it at the point of attachment. This lastoperation leaves that burr or roughness which is seen atthe bottom of all glass unless taken off by grinding.

Decanters are rather a more complicated piece ofworkmanship, the shape being given from the globewhile it still remains on the iron tube. The flat orupper part of the instrument is used for this purpose,which, by alternately pressing against the glass in theparts required to be flat, and blowing through the tube,the body of the decanter is soon brought to the proposedshape. A workman now brings the iron rod with apiece of melted glass, which he attaches concentricallywith the bottom of the decanter; the other workmanat the same time applies the cold iron rod moistenedwith water to the other end, and the glass vessel is bythis means almost instantaneously transferred to the ironrod. The decanter has now to be again heated, in orderto form the mouth part, which is done bv first smooth-ing the end very truly, by introducing the prong end ofthe tool, and bringing it into a position nearly at rightangles with the axis of the decanter. The rings whichare formed on all decanters are still to be added, whichis done by the addition of fresh glass. An assistantworkman brings an iron rod, provided with the requiredquantity of melted glass, which he applies at the partwhere the ring is intended to be made, and the work-man at the same time turning the decanter, a ring ofmelted glass is caused to encircle it, which is madeof the required shape by a gauge contained in theinner part of one of the prongs of the above-mentioned

tool. In the same way the remaining rings are put on,which being done, the decanter is again introducedinto the mouth of a glass pot, and brought up to aconsiderable heat, in order that the rings may be wellfused with the body of the metal. The decanter is nowcomplete, with respect to shape, but is again submittedto the turning operation as it cools, to be rendered smoothand perfectly true in every part.

The manner in which all other round glass vesselsare formed is similar to that described above, so thatit is unnecessary to enter into any further descriptionof them. Vessels which are not of a round figure can-not, however, be accomplished by these means : it is thennecessary to have a mould, in which the glass is placewhile it is blown, which causes it to take any impression

with the most complete precision. . ^ m) eai

(695.) Annealing .—Another important process isrequired before the glass vessel is fit for use, viz. that oannealing, without which it will always be liable to yby the least change of heat and cold, by the sma esscratch, or even without any apparent external cause.

This process consists in allowing the glass to cool vegradually in a low chamber built lor the purpose, > ,eathe furnace, which is sufficiently hot at one end to cepthe glass in a state approaching to softness, but graally diminishing in heat towards the further en , ■that being introduced at one end, and pusheward as new articles are brought up, it arrives by e o 'at a cooler part of the oven, and finally at the 0 , .extremity, where the temperature does not exceed

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