The arrangements so far apply equally to all kinds of glass. We now, however, return to the manufacture of glass bottles, in order the more fully to understand which, we give the following a-round-Dian of one of the houses iu which this is carried on (fig. 1): a is the main furnace, which in this case is square, and made to hold only four pots; at each corner is an opening, which allows the fire to enter four small reverberatory furnaces, b, b, b, b, called arches; two are called the coarse arches, and the others the fine arches. In the two former, the soapmakers' waste is calcined at a red heat for at least four hours, or whilst a set of pots is being worked out—that is to say, one journey. Then the calcined material is ground and sifted in the grinding and sifting house, h, after which it is mingled with the sand, etc., and transferred to the fine arches, where for the term of another journey it is again calcined. At the end of that time, the pots being empty, are refilled with this material.
When the furnaces are opened for a journey, the skimmer first removes the scum, and makes the way clear for the blower and molder, who takes Its blow pipe of iron, six feet in length, the part held in the hand being guarded by a covering of wood and other non-conducting materials. After heating the end of the blow-pipe in the furnace mouth, lie dips it into the pot, and turning it round, gathers as much metal on the end as is sufficient to form a bottle of the size required. Usually, in bottle making, one gathering suffices, but in larger operations, such as blowing window glass, more gatherings have to be made. The operator then blows gently down the pipe, and having thus slightly distended the bulb of red hot plastic glass (fig. 2, a), he takes it to a plate of polished iron, forming a low bench called the mazer, or marering table. On this he turns it round, molding the round lump of glass into a conical form, the change being represented in fig. 2, b. This operation, called marering, is performed in all cases where glass is blown; and as it is necessary that the glass should be pretty firm before mavering, it is often cooled by sprinkling with water, and even, as in the case of win dow-glass and other large blowiugs, turning it in a cavity containing water, which is made by hollowing out a block of wood, usually, if attainable, that of the pear-tree, which is said to be best for the purpose.
After mavered, the glass is held to the mouth of the furnace, and the operator blows down his blow-pipe, and further distends his glass. Formerly, he commenced molding it into the form of a bottle with his shears, one arm of which was of charred wood, and the concave bottom was made by pushing a little piece of glass, called a punty, at the end of an iron rod called the pointel; the blowpipe was then detached by a slight blow of the shears, and the partly formed bottle was.left at the end of the poin
tel attached by the punty in the hands of a boy who attends upon the man, and brought and applied the punty. The man then took the pointel in one hand, end after softening the bottle in the mouth of the furnace, molded the neck by means of his shears, regu lating the size of the opening by means of a small brass mold, the size and shape of a cork, attached to the middle of the shears; heating the neck again, he formed with a small portion of metal from the pot the ring round the mouth of the bottle. Now, how ever, after mavering, and the first slight blowing, the operator inserts the glass into an iron or brass mold, which is formed in two pieces, opening or closing by the pressure of the foot on a lever. When the mold is closed, he blows down the pipe, and the bot tle is completed all but the neck, the ring of which has to be formed by the addition of a fresh piece of metal, as before described. By this process, bottles are made with wonderful rapidity and exactness. At this stage of the manufacture, by either process, the bottles are taken from the workman by a little boy, who inserts the prongs of a fork into the necks, and carries them to one of the annealing arches, d, d, d, d, d, d, where they are carefully arranged in proper bins until the arch, which usually holds i 144 dozen, is full; it is then closed, and the heat is raised nearly to softening point, and then allowed gradually to subside until it becomes cold, when the bottles are removed to make room for a fresh charge. In the plan, fig. 1, e and f are the sand and alkali stores; g, g, are stores for the prepared frit; and i, j, are sifting-cribs in the sift ing-house.
Window-glass, whether crown or sheet, is made of much more carefully selected mate rials. They are slightly varied by different manufacturers, but the following are the ingredients used in one of the largest glass-houses in Great Britain: sand (well dried), from the neighborhood of Leighton Buzzard, in Bedfordshire; sulphate of soda, ground; subearbonate of soda, white oxide of arsenic, manganek, Welsh anthracite, chalk; lime stone from Hopton wood, Derbyshire; nitrate of soda; cullet, about as much as is equal to an eighth part of the other ingredients. The exact proportions are only known to the manufacturers. Each ingredient is carefully powdered before mixing, and they are afterwards calcined or fritted, except the anthracite, which is added in the pot for the purpose of decomposing the sulphate of soda, and dissipating its acid; and the mangan• ese and arsenic, which are only added in very small quantities, to improve the color; too much, however, of each is sure to injure the glass, and therefore these materials can only be safely used by experienced manipulators. The bulk of the glass, however, consists of the sand, and carbonate and sulphate of soda.