[Fig. 509.] is an elevation of the flashing furnace. The outside is built of common brick, the inside of fire-brick, and the mouth or nose of Stourbridge fire-clay.
[Fig. 510.] is the annealing kiln. It is built of common brick, except round the grate room, where fire-brick is used.
Few tools are needed for blowing and flashing crown-glass. The requisite ball of plastic glass is gathered, in successive layers as for bottles, on the end of an iron tube, and rolled into a pear-shape, on a cast-iron plate; the workman taking care that the air blown into its cavity is surrounded with an equal body of glass, and if he perceives any side to be thicker than another, he corrects the inequality by rolling it on the sloping iron table called marver, (marbre). He now heats the bulb in the fire, and rolls it so as to form the glass upon the end of the tube, and by a dexterous swing or two he lengthens it, as shewn in I, [fig. 511.] To extend the neck of that pear, he next rolls it over a smooth iron rod, turned round in a horizontal direction, into the shape K, [fig. 511.] By further expansion at the blowing-furnace, he now brings it to the shape L, represented in [fig. 511.]
This spheroid having become cool and somewhat stiff, is next carried to the bottoming hole (like [fig. 509.]), to be exposed to the action of flame. A slight wall erected before one half of this hole, screens the workman from the heat, but leaves room for the globe to pass between it and the posterior wall. The blowing-pipe is made to rest a little way from the neck of the globe, on a hook fixed in the front wall; and thus may be made easily to revolve on its axis, and by giving centrifugal force to the globe, while the bottom of it, or part opposite to the pipe, is softened by the heat, it soon assumes the form exhibited in M, [fig. 511.]
In this state the flattened globe is removed from the fire, and its rod being rested on the casher box covered with coal cinders, another workman now applies the end of a solid iron rod tipped with melted glass, called a punto, to the nipple or prominence in the middle; and thus attaches it to the centre of the globe, while the first workman cracks off the globe by touching its tubular neck with an iron chisel dipped in cold water. The workman having thereby taken possession of the globe by its bottom or knobbed pole attached to his punty rod, he now carries it to another circular opening, where he exposes it to the action of moderate flame with regular rotation, and thus slowly heats the thick projecting remains of the former neck, and opens it slightly out, as shewn at N, in [fig. 511.] He next hands it to the flasher, who resting the iron rod in a hook placed near the side of the orifice A, [fig. 509.], wheels it rapidly round opposite to a powerful flame, till it assumes first the figure O, and finally that of a flat circular table.