Bottle-Brush Plants

BOTTLE-BRUSH PLANTS, a genus of Australian plants, known botani cally as Callistemon, and belonging to the myrtle family (Myrtaceae) . They take their name from the resemblance of the head of flowers to a bottle-brush. They are well known in cultivation as green house shrubs ; the flower owes its beauty to the numerous long thread-like stamens which are much larger than the small petals. There are 12 species.

B O T T L E MANUFACTURE. Many glass articles are covered by the term "bottle" as used in the industry, wide-mouth bottles, jars and cheap glass tumblers used as containers for jam or other foodstuffs being included, whilst the . _ capacities run from a fraction of a fluid ounce for bottles to 15 gallons for carboys. The industry is widespread and constitutes a relatively important part of glass manufacture. Evidence of this is seen in the following table : The Soviet Union Year Book for 1927 states that for the year 1925-26, 89,478 tons' of bottles were manufactured, the total weight of all glass articles being tons.

In England, bottle-making has for long constituted a very im portant branch of glassmaking. It is computed that 240,000 dozen bottles were produced in England in 1695 and Houghton, in his Letters on Trade (1696), gives a list of 88 glass factories, of which 39 made bottles. Statistics derived from the excise period when glass was taxed show that in 177o the weight of common bottles was 283,54ocwt. out of a total glass production of 411,o5ocwt. ; in 1800, 314,15ocwt. out of 487,85ocwt.; and in 1840 (a year of more than average production), 462,o7ocwt. out of 728,000cwt.

Statistics of production in recent times are available only for Great Britain, the United States and Canada, obtained by a census of production. The latest available data for the U.S. and Great Britain are : An idea of the very great increase in productive efficiency ob tained by the wholesale introduction of machinery is gained from the fact that in 1899 the number of wage earners in the U.S. bottle industry was 28,37o and the production 7,780,000 gross, whereas in 1925 the wage earners numbered only but the bottles made numbered 26,044,000 gross. In Great Britain the productive effi ciency has also been greatly raised. Several factories now make three-quarters of a million bottles and more per week. On the con tinent of Europe, efforts are being made to follow the lead set by the U.S. and by Great Britain to stimulate output by the greater use of automatic machinery.

In the United States, the value of the glass bottle (or glass con tainer) production ($100,3o1,407) is greater than of either plate glass or ordinary window glass, and only a little less than the total ($1o7,961,501) for all forms of sheet glass. The same is true of Great Britain, the aggregate for all forms of sheet glass being f6,o58,000. The United States is the greatest producer in the world of glass bottles or containers as she is of sheet glass in its various forms.

Constituents of Glass for Bottles.

Glass for bottle-making is composed chiefly of three oxides, namely, silica (the chemical compound which constitutes quartz or silver sand), soda (sodium oxide) and lime (or calcium oxide). Other oxides may be present and their amount, as well as that of the chief constitu ents, is controlled by various factors including (a) the colour re quired, (b) the size of the bottle, (c) the method of manipulating the glass, whether by hand or by machine, (d) the conditions to which the bottle is to be subjected in use.

For making colourless glass, sand containing not more than o•o5 o•o6% of iron oxide must be employed ; the iron oxide in the source of lime should not exceed o• 1 %—in Great Britain it is usu ally kept below o.o5%—the iron oxide in the glass should not be more than o.09%. Pale green bottle glass may contain be tween 0.15 and o.5% of iron oxide (ferric oxide) . The dark green bottles made in Great Britain and Europe for beer or whisky or wine contain usually 1.5-2.5%. Inferior sands may, conveniently be used for dark green bottle glass. These impure sands also intro duce alumina, from the clay or other mineral residues associated with them, which bestows on the glass toughness and diminished tendency to crystallize. In bottle factories on the Continent alumina is added to glassmaking mixtures in the form of some aluminous mineral, such as phonolith, disintegrated granite or vol canic rocks. Finally, the lime employed may contain magnesia. Indeed, in the Eastern U.S., the commercial limes most free from iron oxide are the dolomitic or magnesian limestones, and these are accordingly used widely there in making colourless glass.

The shades of green imparted by iron oxide may be modified by black oxide of manganese (2-3% in the glass), by which an olive green or golden green may be obtained according to both the relative and the total amounts of the oxides. The so-called "actinic" green glass is made by the addition of chromium oxide; such glass is melted in pot furnaces (see below) . Amber glass melted in pots is usually coloured by a mixture of iron oxide (1.5– 2.5 % in the glass) and manganese oxide (2-4%) ; or, in tank fur naces, by a mixture of carbon (as coal, or graphite) and sulphur. Blue bottle glass is obtained by the addition of a small amount of cobalt oxide.

The chief raw materials for bottle glass are sand, soda ash (sodium carbonate), saltcake (sodium sulphate) and limestone or burnt lime or slaked lime. A mixture from which colourless glass for automatic machine op eration is made contains : sand (iron oxide less than o•06%) soda ash 330-40o; salt cake 1 o-15; pure limestone 18o 23c) (or 100-130 if burnt lime) ; white arsenious oxide 0-2. In addition, 300-600 parts of broken waste (colourless) glass, known as cullet, are added. To neutralize the greenish tinge of even small amounts of iron oxide, a "decolourizer" is added, con taining essentially the element selenium with cobalt oxide, on the average about to 1 oz. of the former and 1- oz. of the lat ter per i,000 lb. of sand.

An increase in the lime con tent and reduction in the soda content increases the rate of set ting of the glass, and hand-made bottles usually contain more lime and less soda than the automatic machine-made. Soda increase re duces the resistance of the glass bottles to the action of water or of fluid preparations placed in them, and bottles or jars should not contain more than 18% soda. Milk bottles and food con tainers which have to be processed under steam pressure should contain less than 17%.

Melting the Glass.

In modern plants the raw materials are weighed out and mixed in rotating drums, the broken cullet often being added at this stage. The melting may be done in fireclay pots in pot furnaces for the special qualities of chemists' bottles, but probably 98-99% of all bottle glass is now melted in tank furnaces (see GLASS). Figs. 1, 2 and 3 are outline sectional plans of such furnaces, the first for supplying hand-workers or semi automatic machines, the second for gravity-fed machines, the third for Owens or Redfern machines.

The mixture of raw materials is fed into the melting portion of the furnace, heated by crossflames emerging from burners or ports, travels forward by a submerged passage into a cooler zone, and thence either to "working holes" or, by way of covered fire clay channels or a revolving shallow fireclay pot, to machines. Of gravity-fed automatic machines one up to eight may be operated by a single furnace; of Owens machines one or two.

Making the Bottle by Hand.

In making the bottle by hand the precise quantity of glass for the bottle is skilfully gathered by rotation as a ball on the end of an iron blowpipe, like treacle on a spoon, smoothed by rolling on a smooth slab of iron or stone (called a "marver"), and distended by blowing a cavity into it and subsequently swinging the marvered glass until it is pear shaped. It is then lowered into a hinged iron mould which is closed round it, and the glass is fully blown up to shape. The ragged-edged neck, as broken from the pipe, is next softened in a small subsidiary furnace and the soft glass pressed back by a tool to form a smooth, thickened lip. Thus the body is made first and the neck last.

Modern Bottle-Making Machines.

In machines, whether semi- or fully automatic, the neck is made first. Certain types of wide-mouth glass containers are made on automatic presses con sisting essentially of a series of moulds (eight or ten) mounted on a circular rotating table with compressed air-operated plungers which descend into the molten glass and press out the article re quired (fig. 4).

With other machines the oper ations are three, namely, the f or mation of (a) the neck, (b) the parison or embryo of the body, (c) the completely blown-up and finished bottle, although proc esses (a) and (b) are combined. Corresponding to each of these operations is a separate cast-iron mould, namely, a neck or ring mould, a parison or blank mould, and a finishing mould. The neck mould is always fitted to the parison mould, above it when used in conjunction with a press and-blow machine or when the parison mould is filled by suction in a blow-and-blow machine.

In the press-and-blow machines (Hartford-Empire, W. J. Miller, Edward Miller and Moorshead machines), the complete parison (with neck) is made by a plunger which descends into the molten glass contained in the mould (fig. 5) . It is then lifted out mechani cally from the parison mould, transferred to the finishing mould and blown up to full size (fig. 6) by compressed air (about 40 lb.

pressure) . All the moulds are hinged, and open and shut auto matically.

In the suction-filled parison mould adopted in the machines by Owens and more recently in the Redfern, Roirant and McNish . -- machines, a cast-iron plug is set within the neck mould and the glass sucked up (from a revolving shallow pot supplied by the main tank in the case of the Owens and Redfern machines) until it completely surrounds the plug (figs. 3 and 7). Subse quently the parison is automatically transferred to a finishing mould and blown up.

In the other type of blow-and-blow machine (Cox, O'Neill, Lynch, W. J. Miller, Edward Miller and Hartford-Empire ma chines) the parison mould is inverted over the neck or ring mould so that the parison is formed in an inverted position. The charge of glass is dropped into the open end of the parison mould and flows down and round the plug fitted into the ring mould, being assisted in the process by compressed air blown in at the top (fig. 9) ; then the plug is withdrawn, a blowing head is intro duced into its place, and sufficient air is blown in to form a dis tinct cavity in the parison (fig. Io). Automatically the parison is turned upwards, transferred to the finishing mould (fig. 11) and blown up fully.

The first bottle-blowing machine was invented by Ashley in England in 1887 ; the first fully automatic machine by Owens in America, between 1899 and 2902. All the later gravity-fed ma chines originated in America. Modern machines comprise a number of units, each consisting of a neck, parison and ring mould, together with actuating mechanisms, blowing and cooling air pipes for machines and attendants, lubricators, etc. In some machines (Owens, Redfern, Graham, Moorshead) these units are mounted on arms radially from a central pillar ; in pressing and in some press-and-blow machines (W. J. Miller, Edward Miller and Hart ford-Empire) the moulds are mounted on a single table, whilst in others (O'Neill and Lynch) they are disposed on circular rotat ing tables, the parison moulds on one, the finishing moulds on the other. The later Owens, Redfern and Graham machines are made with 10 or 15 units; the latest O'Neill and Lynch machines carry six parison moulds and eight finishing moulds. The molten glass is supplied to the moulds of O'Neill, Lynch, W. J. Miller, Edward Miller, Hartford-Empire and Moorshead machines by automatic feeding devices. The glass flows from the furnace into the fire clay channels (fig. 2), and is extruded through an orifice by a plunger or needle which rises and descends above it. Shears fixed below the orifice sever the extruded glass which falls into the mould below. These feeding devices (fig. 8) of which the best known are the Hartford-Empire, W. J. Miller and Rankin, were invented in America.

Annealing.

The hot bottles from the machine are conveyed either by hand or, where conditions admit, by a conveyor-belt to the annealing furnace or "lehr" where they cool off at a regulated rate. A lehr consists of a belt, 4 to I2ft. wide, continuously travel ling along a chamber or tunnel about 7of t. long. At the front, where the bottles are inserted, is a combustion chamber about 20 to 2 2 f t. long providing a zone sufficiently hot (S 5o °-600°C.) to remove any stresses in the glass previously introduced by chilling (see GLASS; ANNEALING). The hot zone is heated by gas or oil burners ; but by thorough heat insulation, the heat supplied ex ternally can be reduced, as in the Hartford-Empire Fireless Lehr, to a very small amount, the temperature being maintained by the bottles which are very hot (6 5o °-7 5o ° C.) when they leave the machines. Sorters and inspectors stand at the cold end of the Lehr, carefully but quickly inspect every bottle, and reject defec tive ones.

The productive capacity of the modern machines is very great. A ten-arm Owens machine will produce per minute 3o to 3 5 jars of 2 lb. capacity, and by using multiple moulds on each arm for certain sizes the output can be raised to 130-260. An O'Neill or Lynch machine will produce 100-120 gross of quart bottles per day. Operation is continuous, night and day, including, in some factories, Sunday.

See W. S. Walbridge, American Bottles Old and New (Toledo, Ohio, F. W. Hodkin and A. Cousen, A Textbook of Glass Technology (192s) ; R. Dralle, Die Glasfabrikation (Munich, 1926).

(W. E. S. T.)