Cane-juice varies exceedingly in richness, with the nature of the soil,
the culture, the season, and variety of the plant. It is an opaque
fluid, of a dull gray, olive, or olive-green colour; in taste, balmy and
saccharine; exhaling the balsamic odour of the cane; slightly viscid;
and of a specific gravity varying from 1·033 to 1·106, according to
circumstances. When fresh, it consists of two parts; the one liquid, the
other solid; the latter of which being merely suspended in the former,
and, therefore, separable in a great measure by filtration or repose.
The solid matter consists of fragments of the cellular parenchyma of the
cane, its fibres, and bark, mechanically protruded through the mill;
mixed with a very abundant greenish substance, like that called
_chlorophyle_ by chemists.
When left to itself in the colonial climates, the juice runs rapidly
into the acetous fermentation; twenty minutes being, in many cases,
sufficient to bring on this destructive change. Hence arises the
necessity of subjecting it immediately to clarifying processes, speedy
in their action. When deprived of its green fecula and glutinous
extractive, it is still subject to fermentation; but this is now of the
vinous kind. The juice flows from the mill through a wooden gutter lined
with lead, and being conducted into the sugar-house, is received in a
set of large pans or caldrons, called clarifiers. On estates which make
on an average, during crop time, from 15 to 20 hogsheads of sugar a
week, three clarifiers, of from 300 to 400 gallons’ capacity each, are
sufficient. With pans of this dimension, the liquor may be drawn off at
once by a stopcock or syphon, without disturbing the feculencies after
they subside. Each clarifier is hung over a separate fire, the flue
being furnished with a damper for checking the combustion, or
extinguishing it altogether. The clarifiers are sometimes placed at one
end, and sometimes in the middle of the house, particularly if it
possesses a double set of evaporating pans.
Whenever the stream from the mill cistern has filled the clarifier with
fresh juice, the fire is lighted, and the _temper_, or dose of slaked
lime, diffused uniformly through a little juice, is added. If an
albuminous emulsion be used to promote the clarifying, very little lime
will be required; for recent cane-liquor contains no appreciable portion
of acid to be saturated. In fact, the lime and alkalies in general, when
used in small quantity, seem to coagulate the glutinous extractive
matter of the juice, and thus tend to brighten it up. But if an excess
of temper be used, the gluten is taken up again by the strong affinity
which is known to exist between sugar and lime. Excess of lime may
always be corrected by a little alum-water. Where canes grow on a
calcareous marly soil, in a favourable season the saccharine matter gets
so thoroughly elaborated, and the glutinous mucilage so completely
condensed, that a clear juice and a fine sugar may be obtained without
the use of lime.
As the liquor grows hot in the clarifier, a scum is thrown up,
consisting of the coagulated feculencies of the cane-juice. The fire is
now gradually urged till the temperature approaches the boiling point;
to which, however, it must not be suffered to rise. It is known to be
sufficiently heated, when the scum rises in blisters, which break into
white froth; an appearance observable in about forty minutes after
kindling the fire. The damper being shut down, the fire dies out; and
after an hour’s repose, the clarified liquor is ready to be drawn off
into the last and largest in the series of evaporating pans. In the
British colonies, these are merely numbered 1, 2, 3, 4, 5, beginning at
the smallest, which hangs right over the fire, and is called the
_teache_; because in it the trial of the syrup, by _touch_, is made. The
flame and smoke proceed in a straight line along a flue to the
chimney-stalk at the other end of the furnace. The area of this flue
proceeds, with a slight ascent from the fire, to the aperture at the
bottom of the chimney; so that between the surface of the grate and the
bottom of the teache, there is a distance of 28 inches; while between
the bottom of the flue and that of the _grand_, No. 5., at the other end
of the range, there are barely 18 inches.
In some sugar-houses there is planted, in the angular space between each
boiler, a basin, one foot wide and a few inches deep, for the purpose of
receiving the scum which thence flows off into the _grand copper_, along
a gutter scooped out on the margin of the brickwork. The skimmings of
the _grand_ are thrown into a separate pan, placed at its side. A large
cylindrical _cooler_, about 6 feet wide and 2 feet deep, has been placed
in certain sugar-works near the teache, for receiving successive charges
of its inspissated syrup. Each finished charge is called a skipping,
because it is skipped or laded out. The term _striking_ is also applied
to the act of emptying the _teache_. When upon one skipping of syrup in
a state of incipient granulation in the cooler, a second skipping is
poured, this second congeries of saccharine particles agglomerates round
the first as _nuclei_ of crystallization, and produces a larger grain; a
result improved by each successive skipping. This principle has been
long known to the chemist, but does not seem to have been always
properly considered or appreciated by the sugar-planter.
From the above described _cooler_, the syrup is transferred into wooden
chests or boxes, open at top, and of a rectangular shape; also called
_coolers_, but which are more properly crystallizers or granulators.
These are commonly six in number; each being about one foot deep, seven
feet long, and five or six feet wide. When filled, such a mass is
collected, as to favour slow cooling, and consequent large-grained
crystallization. If these boxes be too shallow, the grain is exceedingly
injured, as may be easily shown by pouring some of the same syrup on a
small tray; when, on cooling, the sugar will appear like a muddy soft
sand.
The criterion by which the negro boilers judge of the due concentration
of the syrup in the teache, is difficult to describe, and depends almost
entirely on the sagacity and experience of the individual. Some of them
judge by the appearance of the incipient grain on the back of the
cooling ladle; but most decide by “_the touch_,” that is, the feel and
appearance of a drop of the syrup pressed and then drawn into a thread
between the thumb and fore-finger. The thread eventually breaks at a
certain limit of extension, shrinking from the thumb to the suspended
finger, in lengths somewhat proportional to the inspissation of the
syrup. But the appearance of granulation in the thread must also be
considered; for a viscid and damaged syrup may give a long enough
thread, and yet yield almost no crystalline grains when cooled. Tenacity
and granular aspect must therefore be both taken into the account, and
will continue to constitute the practical guides to the negro boiler,
till a less barbarous mode of concentrating cane-juice be substituted
for the present _naked teache_, or _sugar frying-pan_.
That weak sugars are such as contain an inferior proportion of carbon in
their composition, was first deduced by me from my experiments on the
ultimate analysis of vegetable and animal bodies; an account of which
was published in the Philosophical Transactions of the Royal Society for
1822. Since then Dr. Prout has arrived at results comfirmatory of my
views. See Philosophical Transactions for 1827. Thus, he found pure
sugar-candy, and the best refined sugar, to contain 42·85 parts of
carbon per cent.; East India sugar-candy, 41·9 parts; East India raw
sugar in a thoroughly dry state, but of a low quality, 40·88; manna
sugar, well refined, 28·7; sugar from Narbonne honey, 36·36; sugar from
starch, 36·2. Hence, by _caramelizing_ the syrup in the _teache_, not
only is the crystallizable sugar blackened, but its faculty of
crystallizing impaired, and the granular portion rendered weaker.
A viscous syrup containing much gluten and sugar, altered by lime,
requires a higher temperature to enable it to granulate, than a pure
saccharine syrup; and therefore the thermometer, though a useful
adjuvant, can by no means be regarded as a sure guide, in determining
the proper instant for _striking_ the _teache_.
The colonial _curing-house_ is a capacious building, of which the
earthen floor is excavated to form the molasses reservoir. This is lined
with sheet lead, boards, tarras, or other retentive cement; its bottom
slopes a little, and it is partially covered by an open massive frame of
joist-work, on which the potting casks are set upright. These are merely
empty sugar hogsheads, without headings, having 8 or 10 holes bored in
their bottoms, through each of which the stalk of a plantain leaf is
stuck, so as to protrude downwards 6 or 8 inches below the level of the
joists, and to rise above the top of the cask. The act of transferring
the crude concrete sugar from the crystallizers into these hogsheads, is
called potting. The bottom holes, and the spongy stalks stuck in them,
allow the molasses to drain slowly downwards into the sunk cistern. In
the common mode of procedure, sugar of average quality is kept from 3 to
4 weeks in the curing-house; that which is soft-grained and glutinous,
must remain 5 or 6 weeks. The curing-house should be close and warm, to
favour the liquefaction and drainage of the viscid caramel.
Out of 120 millions of pounds of raw sugar, which used to be annually
shipped by the St. Domingo planters, only 96 millions were landed in
France, according to the authority of Dutrone, constituting a loss by
drainage in the ships of 20 per cent. The average transport waste at
present in the sugars of the British colonies cannot be estimated at
less than 12 per cent., or altogether upwards of 27,000 tons! What a
tremendous sacrifice of property!
Within these few years a very considerable quantity of sugar has been
imported into Great Britain in the state of concentrated cane-juice,
containing nearly half its weight of granular sugar, along with more or
less molasses, according to the care taken in the boiling operations. I
was at first apprehensive that the syrup might undergo some change on
the voyage; but among more than a hundred samples which I have analyzed
for the custom-house, I have not perceived any traces of fermentation.
Since sugar softens in its grain at each successive solution, whatever
portion of the crop may be destined for the refiner, should upon no
account be granulated in the colonies; but should be transported in the
state of a rich cane-syrup to Europe, transferred at once into the
blowing-up cistern, subjected there to the reaction of bone black, and
passed through bag-filters, or through layers of the coarsely ground
black, previously to its final concentration in the vacuum pan. Were
this means generally adopted, I am convinced that 30 per cent. would be
added to the amount of home-made sugar loaves corresponding to a given
quantity of average cane-juice; while 30 per cent., would be taken from
the amount of molasses. The saccharine matter now lost by drainage from
the hogsheads in the ships, amounting to from 10 to 15 per cent., would,
also be saved. The produce of the cane would, on this plan, require less
labour in the colonies, and might be exported 5 or 6 weeks earlier than
at present, because the period of drainage in the curing-house would be
spared.
It does not appear that our sugar colonists have availed themselves of
the proper chemical method of counteracting that incipient fermentation
of the cane-juice, which sometimes supervenes, and proves so injurious
to their products. It is known that grape-must, feebly impregnated with
sulphurous acid, by running it slowly into a cask in which a few sulphur
matches have been burned, will keep without alteration for a year; and
if _must_, so _muted_, is boiled into a syrup within a week or ten days,
it retains no sulphureous odour. A very slight muting would suffice for
the most fermentable cane-juice: and it could be easily given, by
burning a sulphur match within the cistern immediately before charging
it from the mill. The cane-juice should, in this case, be heated in the
clarifier, so as to expel the sulphurous acid, before adding the temper
lime; for otherwise a little calcareous sulphite might be introduced
into the sugar. Thus the arescence so prejudicial to the saccharine
granulation would be certainly prevented.
An ACCOUNT of SUGAR Imported into the United Kingdom during the years
ending 5th January, 1837, and 5th January, 1838.
+------------------------------+-----------------------------------+
| | Quantities imported. |
| +-----------------+-----------------+
| | 1837. | 1838. |
| +-----------------+-----------------+
| | Cwt. qr. lb.| Cwt. qr. lb.|
|Sugar, unrefined; viz.--of | | |
|the British possessions in | | |
|America |3,600,516 3 2 |3,304,092 2 2 |
|Of Mauritius | 497,303 0 8 | 537,054 1 21 |
|East India British possessions| 152,229 1 13 | 296,677 2 12 |
|East India Foreign possessions| 71,464 2 0 | 77,090 0 18 |
|Other sorts | 327,647 1 12 | 266,559 2 24 |
| +-----------------+-----------------+
|Total |4,649,161 0 7 |4,481,474 1 21 |
+------------------------------+-----------------+-----------------+
+------------------------------+-----------------------------------+
| | Quantities entered for Home |
| | Consumption. |
| +-----------------+-----------------+
| | 1837. | 1838. |
| +-----------------+-----------------+
| | Cwt. qr. lb.| Cwt. qr. lb.|
|Sugar, unrefined; viz.--of | | |
|the British possessions in | | |
|America |3,296,641 1 19 |3,562,703 1 24 |
|Of Mauritius | 518,228 0 5 | 522,348 3 11 |
|East India British possessions| 110,236 2 0 | 270,146 1 2 |
|East India Foreign possessions| 20 3 18 | 3 3 11 |
|Other sorts | 31 1 6 | 37 3 10 |
| +-----------------+-----------------+
|Total |3,925,140 0 20 |4,355,240 1 2 |
+------------------------------+-----------------+-----------------+
+------------------------------+---------------------+
| |Gross amount of Duty |
| | received. |
| +----------+----------+
| | 1837. | 1838. |
| +----------+----------+
| | _£_. | _£_. |
|Sugar, unrefined; viz.--of | | |
|the British possessions in | | |
|America |3,956,879 |4,275,207 |
|Of Mauritius | 621,596 | 626,131 |
|East India British possessions| 176,376 | 368,672 |
|East India Foreign possessions| 66 | 12 |
|Other sorts | 41 | 95 |
| +----------+----------+
|Total |4,754,958 |5,270,117 |
+------------------------------+----------+----------+
An ACCOUNT of SUGAR Exported in the year ended 5th January, 1838,
compared with the Exports of the preceding Year.
+----------------------+-----------------+-----------------+
| | 1837. | 1838. |
| +-----------------+-----------------+
| | Cwts. qrs. lbs.| Cwts. qrs. lbs.|
|Sugar, of the British | | |
| possessions | | |
| in America | 8,774 1 15 | 9,267 0 21 |
| Mauritius | 2,687 3 14 | 3,065 0 19 |
| East India, of | | |
| British posses-| | |
| sions | 22,290 3 16 | 13,283 0 22 |
| Foreign posses-| | |
| sions | 52,384 0 4 | 68,252 2 18 |
| Other sorts |191,961 0 20 |354,513 1 23 |
+----------------------+-----------------+-----------------+
Syrup intended for forming clayed sugar must be somewhat more
concentrated in the teache, and run off into a copper cooler, capable of
receiving three or four successive skippings. Here it is stirred to
ensure uniformity of product, and is then transferred by ladles into
conical moulds, or _formes_, made of coarse pottery, having a small
orifice at the apex, which is stopped with a plug of wood wrapped in a
leaf of maize. These pots are arranged with the base upwards. As their
capacity, when largest, is greatly less than that of the smallest
potting-casks, and as the process lasts several weeks, the claying-house
requires to have very considerable dimensions. Whenever the syrup is
properly granulated, which happens usually in about 18 or 20 hours, the
plugs are removed from the apices of the cones, and each is set on an
earthen pot to receive the drainings. At the end of 24 hours, the cones
are transferred over empty pots, and the molasses contained in the
former ones is either sent to the fermenting-house or sold. The claying
now begins, which consists in applying to the smoothed surface of the
sugar at the base of the cone, a plaster of argillaceous earth, or
tolerably tenacious loam in a pasty state. The water diffused among the
clay escapes from it by slow infiltration, and descending with like
slowness through the body of the sugar, carries along with it the
residuary viscid syrup which is more readily soluble than the granulated
particles. Whenever the first magma of clay has become dry, it is
replaced by a second; and this occasionally in its turn by a third,
whereby the sugar cone gets tolerably white and clean. It is then dried
in a stove, cut transversely into _frusta_, crushed into a coarse powder
on wooden trays, and shipped off for Europe. Clayed sugars are sorted
into different shades of colour according to the part of the cone from
which they were cut; under the denomination in French commerce of
_premier_, _second_, _troisième_, _petit_, _commun_, and _tête_; the
last or the tip being an indifferent article. The clayed sugar of Cuba
is called Havannah sugar, from the name of the shipping port.
Clayed sugar can be made only from the ripest cane-juice, for that which
contains much gluten would be apt to get too much burned by the ordinary
process of boiling, to bear the claying operation. The syrups that run
off from the second, third, and fourth application of the clay-paste,
are concentrated afresh in a small building apart, called the refinery,
and yield tolerable sugars. Their drainings go to the molasses cistern.
The cones remain for 20 days in the claying-house, before the sugar is
taken out of them.
Claying is seldom had recourse to in the British plantations, on account
of the increase of labour, and diminution of weight in the produce, for
which the improvement in quality yields no adequate compensation. Such,
however, was the esteem in which the French consumers held clayed sugar,
that it was prepared in 400 plantations of St. Domingo alone.