It had been observed that, in this glass-melting process, the metal as it "fines"sinks below the surface• and that, consequently. in order to work out the metal to the best advantage, the depth of the tank had to be very considerably increased, so that below the fluid-molten metal there should be a layer of metal in a semi-fluid or partially solid conditim lining the tank. one of the later glass-making patents to Frederick Siemens covered this important point. Ile uses a deep tank. in which there are boats or floating fining-vessels made of refract ory materbd, and provided IciHi projecting horns which serve as fenders to keep them from close-contact with the sides of lank.
Another imjax We MC nt Upon the regenerative to for continuously melting glass consisted in placing the regenerators at the sides of the tank and forming an open cave below the tank, communicating with air-spaces on each side, for the purpose of cooling the bottom and sides and receiving such metal as may leak through in any open accessible space.
A patent was also granted in 1885 for• an improvement in the art of subjecting a charge in a glass-melting tank to the gradual application of heat. consisting of treating such charge in a tank so arranged and adapted that the surface of the molten metal contained therein shall be preserved constantly level, and having a bottom wholly or partially inclined Trona the charging end toward the gathering end, whereby said charge. When ineltol, becomes of vary ing depth iihove said bottom and below the hot gases forming the source of heat. It is claiined for this invention that the heat can he applied more uniformly to the charge o• batch, and the latter becomes more thoroughly fluxed, preventing also the formation of de posits in the tank, or what are technically known as or •'stones." Tank-furnaces are used principally in bottle-works and in the manufactnre of rolled plate, but window-glass of a low grade has also been shown as made in one of these tank-furnaces. In some instances they are fired by common coal from one end. the working-holes being on the other three sides. A new practice, which was introduced in France some few years ago by 31. (len:al:dot, a celebrated glass manufacturer, has found mach favor among glass-makers. It is the coating with nickel of molds. blowpipes• and tools used in glass-blowing. This coat ing prevents the oxide of iron from being introduced into the glass from impure cutlets.
Codling Olass.—Several attempts have been made to cut glass by machinery, but up to within a few years no oinsiilemble amount of success has been met with. There was a ma chine in operation at the Exposition which had just been brought out, and was supposed to be for cutting several tumblers at a time, although only single glasses wrc?e cut in public.
The tumbler was mounted upon a holder !pressing upon the face of a horizontally revolving wheel, the holder being weighted sv1fic•iently to give the proper pressure to grind out the flutes. The apparatus was automatic, raising and revolving the tumbler a sufficient distance to cut the next flute, and again lowering it against the grinding-wheel, repeating the opera that until all the flutes around the tumbler are cut. There does not appear to have been any means for regulating the penetration of the grinding-wheel, pressure being simply depended upon for action.
An A meriean machine, invented by 3lessrs. Charles & d. P. Colm% has been used for some years in the successful emitting of decanters, goblets, sug,ar-bowls. mustard-pots. tumblers. etc. It is not entirely automatic. but is adapted to cut all geometrical shapes and patterns, as well as a great variety of styles of cutting. The rapidity, the regularity. and the perfection of the work dome with this maehine insure considerable saving in the original cost price of cut art ieles.
Preaxing or ,1/0/ding ckm.s,___whpu pressing glass continuously for a long time the molds often get healed too high, and in this state glass is very apt to stick to them. This incon venience is now done away with by a system of blowing air into the molds, lty means of a revolving ran or other device, and tin pipes arranged around the furnace. a vont him ins stream of air is furnished. India-rubber pipes are attached to the tin pipes at suitable places. Ity means a Ihese pipes. after each pressina, (a. as often as 1,,,,sary. a steam of air is scup on side of the mold. thereby cooling it. The air circulating in the pipes may also be used for Yon flat ion and for cooling the glass-house. Of late, attempts have been made to use presses for pressing glass by steam or conuiressed air. One of these presses has a set of molds carried upon a revolving bed. and is operated by a presser like a hand-press. The power. however, is aPplied to I he presser by Inv:111S of an auxiliary sty:on-engine, which is continually at work. Whruraer an article is 1,, be pressed, by suitable leverage the presser is forced down, I hen re lra,ed t he bed-plate revolves fa• enough to bring another mold under 1 he pi•esser, and the operation is repeated as often as desired. Nlechnnisin is attached and operated also by sterna se is to push the r.ieves of the mold after they are pressed. These are the principal foninres of the invent ion.