[Illustration: BOILING HOUSE.]
Although sugar was known from very early times, it was used only in
medicine, and was supposed to be a sort of honey found upon canes in
India and Arabia. It is frequently mentioned by the very early writers.
The culture of the canes seems to have been confined to the islands
of the Indian Archipelago, and the kingdoms of Bengal, Siam, &c. The
traffic in sugar was so lucrative that the Indians concealed the mode
of preparing it, stating to the merchants of Ormus, who imported it
with gums and spices, that it was extracted from a reed, whereupon many
unsuccessful attempts were made to find it in the reed-like plants of
Arabia. In 1250 the great discoverer, Marco Polo, visited the country of
the sugar cane, and the merchants afterwards sent to the place of its
growth, instead of buying it at Ormus. For a long period the use of sugar
in England was confined to medicines, or to preparing choice dishes at
feasts; and this continued till 1580, when it was brought from Brazil to
Portugal, and thence to our country.
Cultivators distinguish three great varieties of canes—the Creole, the
Batavian, and the Otaheite. The Creole cane is indigenous to India, and
was transplanted thence to Sicily, the Canary Isles, the Antilles, South
America, and to the West Indies. It has dark green leaves, and a thin
but very knotty stem. The Batavian or striped cane, which has a dense
foliage, and is covered with purpled stripes, is a native of Java, where
it is chiefly cultivated for the manufacture of rum; it is also met
with in some parts of the New World and the West Indies. The Otaheite
variety grows most luxuriantly, is the most juicy, and yields the largest
product. It is cultivated chiefly in the West Indies and South America;
it ripens in ten months, and is hardier than the other varieties.
The sugar cane, being originally a bog-plant requires a moist, nutritive
soil, and a hot tropical or sub-tropical climate. It is propagated by
slips or pieces of the stem, with buds on them, and about two feet long.
It arrives at maturity in twelve or sixteen months, according to the
temperature; the leaves fall off towards the following season, and the
stem acquires a straw-yellow colour. The cane is cut by some planters
before the flowering season, but it is more usual to cut it some weeks
after. The plantations are so arranged that the various divisions of
the fields may ripen in succession. The land should be supplied with
manure rich in nitrogen, but not containing much saline matter. After the
harvest the roots strike again, and produce a fresh crop of canes; but in
about six years they require to be removed.
The time for cutting the canes varies with the soil and season, and the
different varieties of cane. In a state of maturity the canes are from
six feet to fifteen feet in length, and from one and a half inch to
two inches in diameter. The usual signs of maturity are a dry, smooth,
brittle skin, a heavy cane, a grey pith, and sweet and glutinous juice.
Canes should be cut in dry weather, or the juice will be found diluted
with an excess of water. When cut they are tied up in bundles, and
conveyed to the crushing mill, particular attention being paid that
the supply should not exceed the demand, otherwise the cut canes would
ferment and spoil.
The sugar cane grows from pieces or slips of itself, containing germs,
and these develop rootlets at the joints, which draw sustenance to
the young shoot as it increases. In the course of time the buds in
the radicle, or root-joints of the first cane, throw out roots, and
form a radicle for a second stem; and in this way, under favourable
circumstances, several canes are produced from the parent stock for
a period of about six years, and sometimes for several more. They,
however, diminish every year in length of joint and circumference, and
are inferior in appearance to the original plant; but they yield richer
juice, and produce finer sugar.
[Illustration: Filtering Bag.]
The sugar exists in the cells of the cane in a state of solution, and
is extracted therefrom by pressure. With this, as with other branches
of industry, science has of late years stepped in, and has greatly
facilitated the process of extraction and manufacture. It may be as well
to give here a summary of the processes employed in the preparation of
raw sugar: The canes are passed through the mill, and the juice thus
extracted from them runs from the mill into a tank, whence it is pumped
to cisterns for supplying the _clarifiers_, heated by steam, where it
is purified. From thence it is run into _bag filters_, by which the
mechanical impurities are removed. It is then run into _charcoal filters_
to remove the colouring matter of the juice. The filtered juice is then
run off into tanks and is drawn thence by vacuum into the _vacuum pan_,
where it is granulated, and from whence it is finally discharged for
packing. When the steam clarifiers are not employed the cane juice is run
into a series of pans or _teaches_ over open fires. This apparatus is
also known as a “battery,” and forms another method of purification.
[Illustration: Stirring Rod. Ladle. Scraper. Crowbar Wrench.]
The original crushing apparatus of India was a kind of squeezing mortar,
made out of the hollow trunk of a tamarind tree, and worked by a yoke of
oxen, the pestle or stamper being a strong beam eighteen feet long, and
rounded at the bottom so as to squeeze or crush the canes in the mortar.
Mills similar to those used for crushing oil seeds were used—as were also
several other forms of apparatus—before rollers were introduced. Stone
and iron rollers were first used, with the axes in a vertical position,
but the horizontal was soon found to be the more convenient and
economical. The importance of a systematic mechanical arrangement appears
to have awakened attention during the reign of Charles the Second, for
in 1663, Lord Willoughby and Lawrence Hyde (second son of Edward, Earl
of Clarendon, High Chancellor of England) associated themselves with
one David de Marcato, an inventor, and obtained a patent for twenty-one
years for making and framing sugar mills. In 1691, John Tizack patented
an engine for milling sugar canes, &c.; but in this, as in the previous
case, it is not specified how the mill should be made. Later on in 1721,
William Harding, a smith, of London, who had been many years in Jamaica,
and was skilled in the manufacture of sugar mills, having observed their
imperfections, how that they were chiefly made with large wooden cogs
cased with iron, endeavoured while abroad to improve their construction,
but failed for want of competent workmen. On his return to London he
made models of sugar mills which were approved by the Royal Society.
These mills were fitted with cast iron rollers and cog wheel gearing,
and were worked by water power; from description they appear to be the
type of mills of the present day. Some forty-five years later, Yonge and
Barclay, ironfounders, of Allhallowslane, City, applied friction wheels
to sugar mills. In 1773, John Fleming, a mill carpenter, proposed an
arrangement of windmill sails which turned a vertical timber shaft shod
with iron, and which gave motion to two hard wooden rollers, between
which the cane was guided and squeezed. In 1807, H. C. Newman, of St.
Christopher, West Indies, designed a mill to be worked by horse power. He
used cog and crown wheels to give motion to three upright rollers, and
the arrangement was considered one which greatly augmented the power
and execution of this class of machinery. In 1821, John Collinge, of
Lambeth, improved cast iron sugar mills by casting the rollers on wrought
iron shafts, instead of keying them on, as previously done. In 1840,
James Robinson patented improvements in sugar mills, which consisted in
using four rollers, one large one and three smaller ones beneath, placed
horizontally, and gearing by cogs into each other. Up to that time three
rollers only appear to have been used. He also proposed to use six
rollers, which are fed from an endless band passing over the rollers. He
cast the rollers and shafts in one piece, cored out to admit steam to
facilitate the extraction of the juice from the cane during crushing.
He also proposed to tin the interior of vacuum pans, &c. Various other
arrangements have been patented, but it is unnecessary here to enumerate,
much less to describe, them. The foregoing examples give an idea of the
progress of the subject during nearly two hundred years. The last ten
years have seen rapid strides made in improving the make of mills, and
the general arrangement of sugar works.
[Illustration: Sparla. Trowel. Chisel. Hammer. Loosening Stove. Crowbar
Hammer. Scoop for filling Moulds.]
Cane juice, as expressed by the mill, is an opaque, slightly viscid
fluid, of a dull grey, olive, or olive green colour, and of a sweet balmy
taste. The juice is so exceedingly fermentable that, in the climate of
the West Indies, it would often run into the acetous fermentation in
twenty minutes after leaving the mill, if the process of clarifying were
not immediately commenced.
The processes followed in the West Indies for separating the sugar
from the juice are as follows: The juice is conducted by channels from
the mill to large flat-bottomed _clarifiers_, which contain from three
hundred to a thousand gallons each. When the clarifier is filled with
juice, a little slaked lime is added to it; and when the liquor in
the clarifier becomes hot by a fire underneath, the solid portions of
the cane juice coagulate, and are thrown up in the form of scum. The
clarified juice, which is bright, clear, and of a yellow wine colour, is
transferred to the largest of a series of evaporating coppers or pans,
three or more in number, in which it is reduced in bulk by boiling; it
is transferred from one pan to another, and heated until the sugar is
brought to the state of a soft mass of crystals imbedded in molasses—a
thick, viscid, and uncrystallizable fluid. The soft concrete sugar is
removed from the coolers into a range of casks, in which the molasses
gradually drains from the crystalline portion, percolating through spongy
plantain stalks placed in a hole at the bottom of each cask, which act
as so many drains to convey the liquid to a large cistern beneath. With
sugar of average quality, three or four weeks is sufficient for this
purpose. The liquid portion constitutes molasses, which is employed to
make rum. The crystallized portion is packed in hogsheads for shipment as
raw, brown, or muscovado sugar; and in this state it is commonly exported
from our West Indian colonies.
[Illustration: Besom. Lump Mould. Loaf Mould.]
The refining of sugar is mainly a bleaching process, conducted on a large
scale in England. There are two varieties produced by this bleaching,
viz. clayed and loaf sugar. For clayed sugar, the sugar is removed from
the coolers into conical earthen moulds called formes, each of which has
a small hole at the apex. These holes being stopped up, the forms are
placed apex downwards in other earthen vessels. The syrup, after being
stirred round, is left for from fifteen to twenty hours to crystallize.
The plugs are then withdrawn, to let out the uncrystallized syrup; and
the base of the crystallized loaf being removed, the forme is filled up
with pulverized white sugar.
This is well pressed down, and then a quantity of clay mixed with water
is placed upon the sugar, the formes being put into fresh empty pots.
The moisture from the clay, filtering through the sugar, carries with
it a portion of the colouring matter, which is more soluble than the
crystals themselves. By a repetition of this process, the sugar attains
nearly a white colour, and is then dried and crushed for sale.
But loaf sugar is the kind most usually produced by the refining
processes. The brown sugar is dissolved with hot water, and then filtered
through canvas bags, from which it exudes as a clear, transparent, though
reddish syrup. The removal of this red tinge is effected by filtering the
syrup through a mass of powdered charcoal, and we have then a perfectly
transparent colourless liquid.
In the evaporation or concentration of the clarified syrup, which forms
the next part of the refining process, the boiling is effected (under the
admirable system introduced by Mr. Howard) in a vacuum, at a temperature
of about 140° Fahrenheit. The sugar pan is a large copper vessel, with
arrangements for extracting the air, admitting the syrup, admitting
steam pipes, and draining off the sugar when concentrated. In using the
pan a quantity of syrup is admitted, and an air pump is set to work to
extract all the air from the pan, in order that the contents may boil
at a low temperature. The evaporation proceeds, and when completed the
evaporated syrup flows out of the pan through a pipe into an open vessel
beneath, called the _granulating vessel_, around which steam circulates,
and within which the syrup is brought to a partially crystallized state.
From the granulators the syrup or sugar is transferred into moulds of a
conical form, which were formerly made of coarse pottery, but are now
usually of iron. In these moulds the sugar whitens and crystallizes, the
remaining uncrystallized syrup flowing out at an opening at the bottom
of the moulds. This syrup is reboiled with raw sugar, so as to yield an
inferior quality of sugar; and, when all the crystallizable matter has
been extracted from it, the remainder is sold as treacle. The loaves of
sugar, after a few finishing processes, are ready for sale.