We take it for granted that our readers know generally how glass is made. That a mixture of sand and an alkali is fused into a kind of pasty mass. The fusion is effected in pots of refractory clay, of which the general form is something like that shown in the sketch. The mouth of the pot is shown at A. The pots at Val St. Lambert are of various sizes; the largest hold about 16 cwt. of glass. The duration of the pots is very variable; they last sometimes only a few days, at others several weeks or even months, much depending on the quality of the pot. The temperature to which they are exposed is not excessively high. The great thing to be effected in a glass melting furnace is the perfectly equal distribution of the heat. At Val St. Lambert gas is used, generated in Siemens or Boetius producers. There are in all twenty furnaces. They are grouped in threes or fours, in the large buildings, with high roofs. Formerly the furnaces were square, and held each eight melting pots, which did not hold more than 250 kilos. of glass. The modern furnaces each receive from twelve to fourteen melting pots. The modern melting pots as made by the Battersea Plumbago Crucible Company do not seem to be known here.
The peculiarities of the construction of the glass melting furnaces at Val St. Lambert will be gathered from the annexed sketch. The furnace is circular, 14 ft. or 15 ft. in diameter, and from the roof, E, to the floor is about 5 ft. 6 in. high. In the center of the floor is a cylindrical opening, A, through which rises the mixture of gas and air, the latter being introduced through four openings, three of which are shown. Two of the pots are indicated by dotted lines at D D. The equitable diffusion of the heat is effected in the following way: Inside the furnace are constructed as many vertical flues as there are pots. Two of these are shown at G G. They have small openings about 5 in. by 8 in. at the bottom. The course pursued by flame is indicated by the bent arrows. The flame rising strikes the crown, E, and is deflected downward and drawn off by the side flues, which deliver into the second vaulted space, F. In this, in some cases, are annealed the finished articles of glass. In others is fixed a boiler, steam being generated by the waste heat. In others there is no opening at the top of F at H, but there is one at the side instead, through which the flame is led to raise steam in Belleville tubulous boilers. The steam is used to drive the engines in the grinderies. Not much power is required, and it is very easily obtained from the waste heat.
SECTION OF CLASS FURNACE.
The operations of the glass blower have been too often described to need redescription here. One or two points, however, deserve notice. One is the large use made of wooden moulds. In these are formed all kinds of circular articles, such as tumblers and lamp glasses. The moulds are in halves, and are kept soaked with water to prevent them from burning. Inside they become lined with charcoal. The glass blower, getting a knob of glass on the end of his blowing rod, blows a very thick, small bulb; this he then places on the mould, which is closed by a very small boy; in but too many cases mere children, seven or eight years old, are employed. The child holds the two sides of the mould together while the blower rotates the bulb within, blowing all the time. The work is turned out very true. Up to a comparatively recent period the tumbler was cut to the proper depth while hot with a pair of scissors, but this has been abandoned, and an extremely ingenious little machine is now used for cutting lamp glasses, tumblers, etc. The article to be cut is placed vertically on a stand. At the proper height above the stand is fixed a sharp steel point, and by touching the glass against this a very small scratch is made. At the same level is fixed a little mouthpiece through which issues, under pressure, a tiny gas flame, not thicker than a sheet of note paper. This falls on the glass, which is turned round by the woman attendant. The glass is heated in an extremely narrow band all round. The touch of a moistened finger suffices for the complete separation of the two parts of the glass round the heated girdle. In fact, this is a very elegant application to manufacturing purposes of the well known hot wire method of cutting glass so often tried with indifferent success by the enterprising amateur.
Glass grinding is carried out on a very large scale at Val St. Lambert in huge well lighted shops. There are four grinderies at Val St. Lambert, and one at Herbatte, the total number of which is 800, and the floor space occupied is no less than 24,000 square feet. The first steam engine was put down to grind glass in 1836. A great deal of engraving is done with fluoric acid, the vessel to be engraved being protected with wax in which the design is etched. Tilghman's sand blast is also employed, as well as the old copper disk system; flats are ground on tumblers by automatic machinery.
It would be impossible to do more than give a general idea of the operations carried on in this vast establishment, every portion of which was thrown open to the members of the Institution, while numbers of heads of departments went round and answered every question, and explained every detail with a frankness and a courtesy beyond praise. It is impossible to inspect such an establishment as that at Val St. Lambert without feeling how hard is the battle which manufacturers in this country have to fight. There, as we have said, are to be found every advantage of position, and to this is added a body of workmen, active, sober, industrious, among whom is heard no talk of strikes, and who are content to work every day and all day long; such men, directed by heads possessed of no small scientific ability, and re-enforced by the command of ample capital, cannot fail to make a mark in any market, and we only speak the truth when we regret that we have not such works and such men on English soil as there are to be found at Val St. Lambert.