The yeast added to the worts as a ferment, ought to be the best top barm
of the London porter breweries. About 1 gallon of it is requisite for
every 2 bushels of meal and malt worked up in the mashing process; and
of this quantity only a certain proportion is introduced at the
beginning; the remainder being added by degrees, on the second and third
day.
Should the fermentation flag, a little more may be added on the fourth
or fifth day, and the contents of the tun may be roused by an agitator.
About 8 or 9 gallons may be introduced four days in succession to the
quantity of worts extracted from 60 bushels of the farinaceous
materials; or the third day’s dose may be intermitted, and joined to the
fourth on the subsequent day.
Great diversity, and no little caprice prevail among distillers in
respect of the periods of administering the yeast; but they should be
governed very much by the appearance of the fermentation. This process
continues from nine to twelve or even fourteen days, according to
circumstances; the tuns being left quite open during the first five
days, but being covered moderately close afterwards to favour the full
impregnation of the liquor with carbonic acid, as a fermenting agent. In
consequence of the great attenuation of the wort by the generation of so
much alcohol, no good body of yeast continues to float on the surface,
and what is formed is beat down into the liquor on purpose to promote
the fermentation. The temperature of the wash gradually increases till
towards the end of the fourth day, when it attains its maximum height of
about 25° above the pitch of 55° or 60° at which it may have been set.
The time of the greatest elevation of temperature, as well as its
amount, depends conjointly upon the quality of the yeast, the nature of
the saccharo-starchy matter, and the state of the weather. It is highly
probable that the electrical condition of the atmosphere exercises a
considerable influence upon fermentation. We know the power of a
thunderstorm to sour vinous fluids. An experimental inquiry into the
relation between electricity and fermentation, could not fail to prove
both curious and profitable.
The diminution of the density of the wort is carefully watched by the
distiller, as the true criterion of the success of his process. This
_attenuation_, as he calls it, is owing partly to the decomposition of
the sugar, which communicated its gravity to the solution, and partly to
the introduction of the lighter alcoholic particles. Were all the
saccharo-starchy matter resolved into gaseous compounds, the wort would
become water; but since a part of it remains undecomposed, and a portion
of alcohol is produced at the expense of the decomposed part, the degree
of attenuation becomes a somewhat complicated problem in a theoretical
point of view; the density due to the residuary sugar being masked and
counteracted by the spirit evolved. Could the alcohol be drawn off as it
is formed, the attenuation would probably become greater, because the
alcohol checks the fermentative action, and eventually stops it, before
all the saccharum is decomposed. After the wash has taken its highest
degree of temperature, not much more spirit is found to be generated;
were this therefore removed by proper means, the remaining vegetable
matter would undoubtedly yield a further product of alcohol.
In the attenuation of raw-grain wash, the specific gravity seldom
arrives at 1·000; but most commonly stops short at 1·002 or 1·004. When
the vinous fermentation comes to an end, the acetous is apt to commence,
and to convert a portion of the alcohol into vinegar; a result which is
easily ascertained by the increasing specific gravity, sour smell, and
acidulous reaction of the wash upon litmus paper, which remains after
the paper is heated, showing that the red colour is not caused by
carbonic acid.
Fermentation proceeds with more uniformity and success in the large tuns
of the distiller, than in the experimental apparatus of the chemist;
because the body of heat generated in the former case maintains the
action. But I have succeeded in obviating this inconvenience in
operating upon 80 or 90 gallons, by keeping up the temperature, when it
begins to flag, by transmitting hot water through a recurved pipe
plunged into the tun.
We have already mentioned that one gallon of spirits, one in ten
over-proof, is upon the average generated from 11·04 libs. of starch
sugar; hence we conclude that one pound water-measure of spirits at
proof (= 1/10 imperial gallon) is produced from one pound of the
saccharum.
_Malt whiskey._--The treatment and produce of malt distilleries are in
some respects different from those of raw grain. Having been
professionally employed by the proprietors of both, I am prepared to
state the peculiarities of the latter, by an example. 500 bushels of
ground malt are first mashed with 9000 gallons of water, heated to the
temperature of 160° F.: 6000 gallons of worts are drawn off into the
coolers, and let down into the fermenting tun at 68°. From 3 to 4 per
cent. of a mixture of London porter yeast with quick Scotch barm, are
added, and well stirred through the mass. At the end of two or three
days, in general, the fermentation is finished. On the residuary grains
of the malt, from 4500 to 5000 gallons of water at 180° are run, which
after proper mashing as before, are drawn off; then 4500 more are poured
on, the drainage of which is added to the second. Both of these
together, constituting 9000 gallons, are heated next day, and employed
for the mashing of 500 bushels of fresh malt. During the fermentation,
the wash which was set at the spec. grav. 1·065, comes down to water =
1·000.
The wash is distilled in two stills, appropriated to it, of about 800
gallons capacity each, provided with a rotatory chain apparatus for
preventing the lees from adhering to the bottom of the still. Into about
800 gallons of wash 8 lbs. of soap are put. The liquor obtained at this
first distillation is called low-wines. These low-wines are redistilled
in the spirit stills; the first and last portions of liquid being more
or less blue or milky in colour, and rank in flavour, are run into a
separate receiver called the _faints-back_; while the middle portion,
constituting in a well-managed distillery, from three-fourths to
four-fifths of the whole, are received into the spirit-back. The faints
are mixed with a large quantity of water, and redistilled, in order to
free them from the fetid oil derived from the husks of the grain. The
interception of this noxious oil may be best effected by a
self-regulating bath, between the capital of the still and the
refrigeratory, as will be explained in treating of STILLS. The capitals
of the common Scotch stills are made from 15 to 20 feet high, in order
to prevent the chance of the wash boiling over into the worm; and they
are, towards the beginning of the process, struck from time to time with
a rod, and by the sound emitted it is known whether they be empty,
partially filled, or in danger of an overflow; in which case the fire is
damped, by a spout near the furnace door, connected by a leather pipe
with an elevated reservoir of water. When very pure spirits are wished
for, a third or even a fourth distillation is had recourse to; there
being a quantity of water mixed each time with the spirit in the still,
to prevent its acquiring a harsh alcoholic flavour.
According to some experienced distillers from raw grain, the mashing
temperature of the first liquor should not exceed 140° F.; whereas with
malt it may be safely and beneficially 165° or 170°. When rye is used
instead of malt, 90 bushels of it are mixed with 190 bushels of raw
grain, constituting 280 bushels in whole, for the mashing of which 5200
gallons of water are required. An hour and a half more time is necessary
for settling the mashing of the above mixture, than of grain alone. Gin
is made in this way.
The distiller of malt whiskey calculates on obtaining two gallons of
proof spirits from one bushel of malt, in average years. The highest
yield is 20 gallons per quarter of 8 bushels; and the lowest is 16, when
the malt and fermentation are indifferent. The best temperature to set
the fermenting tuns with malt wash is about 70° or 72° F.
When malt is 5_s._ the bushel, 6 bushels at 30_s._ will yield 12 gallons
of proof spirits. These cost therefore 2_s._ 6_d._ per gallon for the
malt; to which must be added 3_d._ per bushel for the amount of malt
duty not returned, or 1-1/2_d._ on the gallon; this added to the Scotch
duty of 3_s._ 4_d._ the gallon, makes the price altogether 5_s._
11-1/2_d._; besides the expenses in fuel, yeast, labour, and rent, which
may be estimated at 8-1/2_d._ per gallon. But 3_d._ may be deducted for
what is paid by the dairymen for the spent wash and grains. The total
cost, therefore, exclusive of use of capital, is 6_s._ 5_d._ per gallon
in Scotland.
The following is the work of a Scotch distillery, where good malt
whiskey was made.
One bushel of the malt weighed 35 libs., or the boll, = 6 bushels, 210
libs. In mashing each boll of malt, 110 gallons of water were run on it
at 160° F. As soon as the fermenting tun of 3000 gallons capacity was
charged with the wash at from 64° to 74° F., 2 gallons per cent. of barm
were added. When the wash had become attenuated from 1·060 to 1·040,
another gallon of barm was introduced.
The temperature of the fermenting wash sometimes rises to 96°, which is,
however, an extreme case, and not desirable. When the bubbles of
carbonic acid mount in rapid succession, it is reckoned an excellent
sign. If the tun be small, and stand in a cool apartment, it should be
started at a higher temperature than in the reverse predicament. Should
the fermentation be suffered to flag, it is in general a hopeless task
to restore vigorous action. Some try the addition of _bubs_, that is of
some wort brought into a state of rapid fermentation in a tub, by a
large proportion of yeast, but seldom with much success. Indeed the law
prohibits the addition of any wort to the tun at a later period than 24
hours after it is set; so that if bubs are used afterwards, the
distiller is apt to incur a penalty.
The maximum quantity of proof spirits obtained on the great scale at any
time from raw grain mixed with from one-fourth to one-eighth of malt,
seems to be 22 gallons per quarter.
By the British laws a distiller is not allowed to brew and distil at the
same time but he must work alternately, one week, for instance, at
fermentation, and next week at distillation.
In fermenting solutions of sugar mixed with good yeast, the attenuation
has been carried down to 0·984, and even 0·982, that is, in the language
of the excise, 16 and 18 degrees below water, from 1·060, the density at
which it was originally set in the tun. This was excellent work done on
the scale of a great distillery nearly 30 years ago, when distillation
from sugar was encouraged, in consequence of bad corn harvests.
In an experiment which I made in 1831 for the information of a committee
of the House of Commons, on the use of molasses in the breweries and
distilleries, I dissolved 1 cwt. of raw sugar in water; so as to form
74-1/2 gallons, inclusive of 2 gallons of yeast. The specific gravity of
the mixture was 1·0593 on the 31st of March. By the 6th of April, that
is in 6 days, the gravity had sunk to 0·992, or 8 degrees under water,
which was reckoned a good attenuation, considering the circumstances and
the small quantity operated upon. By distillation it afforded at the
rate of 14·875 gallons of proof spirits for 100 gallons of the wash.
When the distillers first worked from sugar, they only obtained upon an
average from 1 cwt. 10·09 gallons imp. of proof spirit; but they
afterwards got no less than 11·92 imp. gallons.
The following experiment, which I made upon the fermentation of West
India molasses into spirits, for the information of the said committee,
may prove not uninteresting to my readers. 150 libs. were dissolved in
water and mixed with 2 gallons of yeast, weighing exactly 20 libs. The
wash measured 70 gallons, and had a spec. gravity of 1·0647 at 60° F. In
two days the gravity had fallen to 1·0055; in three days to 1·0022; and
in five days to 1·001. The temperature was kept up at from 80° to 90°
F., during the two last days, by means of a steam pipe, to favour the
fermentation. The product of spirits was 11 gallons, and 35/100 of a
gallon. Now 150 libs. of the above molasses were found to contain of
solid matter, chiefly uncrystallizable, 112 libs. And as 112 libs. of
sugar are estimated by the revenue laws to afford by fermentation 11-1/2
gallons imp. of proof spirit, the result of that experiment upon
molasses must be considered satisfactory, bearing in mind that the
saccharine substance in molasses has been not only partially decomposed
by heat, but is mixed with some of the glutinous or extractive matter of
the cane.
Since the alteration of the excise laws relative to distillation in 1825
and 1826, when permission was given to set the wort at lower gravities,
the quantity of spirits produced from 1 quarter of corn has been much
increased, even up to fully 20 gallons; and the proportion of malt has
been much diminished. The latter was soon reduced from three-sevenths
malt, and four-sevenths barley, or two-fifths malt and three-fifths
barley, to one-fifth of malt, and now to one-tenth or even
one-sixteenth.
A discussion having lately taken place in Ireland between certain
persons connected with the distilleries and the officers of the excise,
whether, and to what extent, raw grain worts would pass spontaneously
into the vinous fermentation, the Board in London requested me to
superintend a series of researches in a laboratory fitted up at their
office, to settle this important point. I shall content myself here with
giving the result of one experiment, out of several, which seems to me
quite decisive. Three bushels of mixed grains were taken, consisting of
two of barley, one half of oats, and one half of malt, which, being
coarsely ground by a hand-mill, were mashed in a new tun with 24 gallons
of water at 155°. The mash liquor drawn off amounted to 18 gallons, at
the density of 1·0465; and temperature of 82° F. Being set in a new tun,
it began to ferment in the course of 12 hours, and in 4 days it was
attenuated down to gravity 1·012. This yielded, upon distillation in low
wines, 3·22 gallons, and by rectification, in spirits, 3·05; while the
quantity equivalent to the attenuation by the tables was 3·31, being an
excellent accordance in such circumstances.
The inquisitorial _regime_ imposed by law upon our distilleries, might
lead a stranger to imagine that our legislators were desirous of
repressing by every species of annoyance the fabrication of the fiery
liquid which infuriates and demoralizes the lower population of these
islands. But alas! credit can be given them for no such moral or
philanthropic motive. The necessity of the exchequer to raise a great
revenue, created by the wasteful expenditure of the state, on the one
hand, and the efforts of fraudulent ingenuity on the other, to evade the
payment of the high duties imposed, are the true origin of that
_regime_. Examinations in distilleries are constantly made by the
officers of excise. There is a survey at 6 o’clock in the morning, when
the officers take their accounts and gauges, and make calculations which
occupy several hours. At 10 o’clock they again survey, going over the
whole premises, where they continue a considerable time, frequently till
the succeeding officer comes on duty; at 2 in the afternoon another
survey takes place, but not by the same people; at 6 in the evening the
survey is repeated; at 10 there comes another survey by an officer who
had not been engaged in any of the previous surveys of that day. He is
not relieved till 6 o’clock next morning. In addition to these regular
inspections, the distilleries are subject to frequent and uncertain
visits of the surveyor and general surveyor. “We are never,” says Mr.
Smith, the eminent distiller of Whitechapel, “out of their hands.”[24]
[24] Report of Committee on Molasses, 2198.
Before the fermented wort goes into the still, a calculation is made of
the quantity of wash drawn from the wash back, and which is first pumped
into what is called the wash charger. If the quantity in the wash
charger exceeds the quantity in the wash back, the distiller is charged
upon the higher quantity; if it contains less, he must pay according to
the wash back, as being the larger quantity. When the quantity of wash
is all transferred to the charger, the discharge cock of the wash
charger is unlocked, and the wash is allowed to be drawn off from the
charger into the still, the charging and discharging cock of the still
being locked by the officer. There can be no transfer of wash but
through the pumps, which are locked also. The first distillation from
the wash is worked into the low-wine receiver, which is also a locked-up
vessel; then of those low wines, the strength and quantity are
ascertained by the excise. The account of them affords a comparison with
the quantity which the contents of the wash-back had been estimated to
produce; they are then pumped from the low-wine receiver, through pumps
previously locked into the low-wine charger, which is also a locked-up
vessel; from the locked-up charger, after the officer has done his duty
regarding it, they are allowed to be drawn off into the low-wine still,
which is a distillation of the second extraction; then that low wine
still works into another locked-up cask, called the spirit receiver, for
the receiving of raw spirits; when that distillation is finished, the
officer, attending again on regular notice for that purpose, takes the
quantity and strength of the spirits therein, and upon the quantity so
ascertained he charges the duty. In distilling low wines, one portion of
them goes into the spirit receiver, and a portion into what is called
the faint receiver, which is another locked-up vessel. These faints are
in the next distillation united with the low wines, from the succeeding
wash-back on their second distillation, and are worked together; the
united produce of these goes partly into the spirit cask, and partly
back again into the faint cask. The operation is thus continued till all
the backs in the house are emptied.[25]
[25] Thomas Smith, Esq., of Whitechapel Road, in Report of Molasses
Committee, Part II. p. 149.
There is a kind of ardent spirits manufactured in Holland, vulgarly
called Dutch gin, Hollands, and sometimes _geneva_, from _genievre_, the
French for juniper, a plant with the essential oil of whose berries it
is flavoured. One cwt. of ground malt mixed with two cwt. of rye meal
are mashed for two hours, with about 450 gallons of water at the
temperature of 160° F. The mash drawn off is reduced with cold water
till the liquid part has the density of 45 libs. per barrel, = specific
gravity 1·047; and is then put altogether into the fermenting back at
the temperature of 80° F. One or two gallons of yeast are added. The
fermentation soon becomes so vigorous as to raise the heat to 90° and
upwards, but it is not pushed far, being generally over in two days,
when the gravity of the wash, still indicates 12 pounds of saccharum per
barrel. By this moderate attenuation, like that practised by the
contraband distillers of the Highlands of Scotland, it is supposed that
the fetid oil of the husks is not evolved, or at least in very small
quantity. The grains are put into the alembic along with the liquid
wash, and distilled into low wines, which are rectified twice over, some
juniper berries and hops being added at the last distillation. But the
junipers are sometimes bruised and put into the mash. The produce of
worts so imperfectly fermented, is probably little more than one half of
what the British distiller draws from the same quantity of grain. But
the cheapness of labour and of grain, as well as the superior flavour of
the Schiedam spirits, enables the Dutch distiller to carry on his
business with a respectable profit. In opposition to the above facts,
Dubrunfaut says that about one third more spirits is obtained in Holland
from grain than in France, because a very calcareous spring water is
employed in the mashing operation. Were this account well founded, all
that the distillers of other countries would have to do would be merely
to introduce a portion of chalk into their mash tuns, in order to be on
a par with the Dutch. But the statement is altogether a mistake.
In the vine countries, the inferior wines or those damaged by keeping,
as also a fermented mash of the pressed grapes, mixed with water, are
distilled to form the _eau de vie de Cognac_ of the French, called
Brandy in this country. It contains less essential oil, and that of a
more agreeable flavour, than corn spirits. See BRANDY.
Berzelius says that there are distillers who are guilty of putting a
little arsenious acid into the still; that the spirits contain pretty
frequently traces of arsenic, which may be detected by adding to them a
little muriatic acid, then evaporating off the alcohol, and passing a
current of sulphuretted hydrogen gas through the residuary liquid, which
will give it the characteristic orpiment yellow tinge, arsenic being
present. Copper, which is sometimes introduced into distilled grain, or
even malt spirits, in consequence of the soap employed in the process of
distillation, may be detected best by the brown precipitate which it
occasions with ferroprussiate of potash. No arsenic is ever used in this
country.
When damaged grain has been mashed in making whiskey, a peculiar oily
substance makes its appearance in it. On approaching the nostrils to
such whiskey slightly heated, this volatile matter irritates the
pituitary membrane and the eyes very powerfully. These spirits have
exactly the smell of an alcoholic solution of cyanogene; they intoxicate
more powerfully than pure alcohol of equal strength, and produce even
temporary frenzy, with subsequent sickness and disordered functions.
This volatile body is not cyanogene, though it be so like it, for it
forms no such combinations as cyanogene does. It may be extracted from
diluted alcohol by agitating it with an unctuous oil, and then
distilling the oil along with water. At the end of 3 or 4 months, this
volatile matter disappears in a great measure, even when the spirits
impregnated with it are inclosed in well-corked bottles; obviously from
its undergoing a spontaneous decomposition. It may be preserved much
longer in the state of a watery solution.
When acetic ether is added to well purified or clean spirits, such as
the distillers call silent whiskey, it gives it somewhat of the flavour
of brandy. For this purpose, also, the spirits are rectified from
bruised prunes, or the lees of the cognac distilleries, whereby they
acquire additional flavour. The astringent taste of old brandy is
imitated by the introduction of a little catechu into the British
spirits. Burned sugar is employed as a colouring in these imitations.
IV. _Of making whiskey from potatos._--This root in certain localities
where it abounds at a moderate price, is an excellent material for
fermenting into alcohol. When sound, it possesses from 20 to 25 per
cent. of solid substance, of which starch constitutes at least
three-fourths; hence 100 pounds contain from 16 to 22 pounds of starch
susceptible of being saccharified. In the expressed juice there is a
small quantity of tartaric acid.
[Illustration: 361]
Previously to mashing, potatos must be first well washed in a horizontal
cylindrical cage revolving partially in a trough of water, as will be
described in treating of the manufacture of sugar from beet root. They
must be then boiled in a close vessel with steam, provided with a
perforated bottom a few inches above the real one. The top has an
opening with a cover fitted tightly to it; through that the potatos are
introduced; and immediately above the false bottom there is a similar
aperture through which the boiled potatos are taken out. The steam-pipe
enters at the top, runs down the side a little way; and terminates in a
widened mouth. The large lids are secured by cross bars, the small hole
by folds of linen. In the lower valve there are two small holes closed
with pins, for inserting a wire to feel whether the potatos be
sufficiently boiled. If so, the steam is immediately stopped off, the
lower lid is removed, and the potatos pulled out with a hook into a tub.
They must be immediately made into a homogeneous paste before they get
cold. _Fig._ 361. represents, in plan, or horizontal section, the
apparatus used in France for this purpose. A B are two cylinders covered
with wire cloth, but open at the ends; C C and D D are two pieces of
wood fixed on the two axes, in the form of two cones, with the adjoining
surfaces truncated; upon which, as also upon iron rings E F, of the same
diameter, made fast to the axes, the wire cylinder rests. Of the two
wheels G, H, the smaller has 18, the greater has 21 teeth. The diameter
of each cylinder is 14 inches, the length 18. Above and between the two
cylinders, there is a hopper for the reception of the boiled potatos.
This machine triturates 1200 pounds of potatos per hour. Their paste
must be forthwith mashed with some ground wheat or barley, and a
proportion of malt; then be set a fermenting.
[Illustration: 362]
As in the above mode of trituration, the potatos are apt to cool to such
a degree as to obstruct their ready admixture with water, it is better
to make them into a paste in the vessel in which they are steamed. The
apparatus contrived by Siemens fully answers this end. It consists
essentially of a tub A, represented in _fig._ 362. in section. It is
cylindrical, and made of planks from 3 to 4 inches thick, joined firmly
and steam-tight; the upper and under ends being well secured with iron
hoops. The lower part is about 2 inches more in diameter than the upper.
About a foot from the bottom, in a circular groove, a cast iron
partition W or disc full of holes is made fast, which serves the purpose
of a scarce, the apertures being an inch asunder; above, from 1/8 to
1/10 of an inch in diameter, and below, scooped out to half an inch.
This disc is half an inch thick in the edges, and five fourths of an
inch in the middle.
Through the female screw _a_ in the top of the cylinder, there passes
the screwed rod _b_, one and a half inches thick, provided at top with a
strong cross bar C C, for turning it round. The under end of this rod
has a square piece terminating in a short screw, upon which a wrought
iron cross is secured by means of a screw nut, so as to stand at right
angles to the rod. This cross is composed of two distinct arms; of which
one of them is mounted on the upper side with little knives an inch and
a half long; the other, upon the under side, with a wire brush, that may
be made to rub against the perforated cast iron disc. On the side of the
cylinder at E, _fig._ 362., there is a narrow aperture provided with a
bung secured by a cross bar, and near the bottom at H there is another
like it. Both openings serve for taking out the residuary matter.
Through the opening E, the above two arms are introduced; and secured to
the square of the rod by the screw nut. In the top there is an opening,
D, for putting in the potatos which may be shut in the same way. From
the lid there likewise issues a lateral tube F, which terminates in a
tubful of water, for condensing the waste steam. G is the tube connected
with the steam boiler, for conducting the steam into the space under the
iron disc W.
With this apparatus the potatos are prepared as follows: when the screw
rod is so fixed that the cross touches the disc, the cylinder is to be
filled with washed potatos to within one foot of the top, leaving them
some space to expand. The orifice D is to be then closed, and the steam
admitted. When the potatos are boiled enough, two labourers lay hold of
the lever handles C C, of the screw rod _b_, and turn it round with the
effect of screwing up the spiked cross, and of triturating the potatos;
an operation which may be still more effectually done by screwing it
down again. The potato paste is now let off by the plug hole H, into the
tub L, where it is mixed with about 30 per cent. of boiling water, and
one thousandth part of potash, made caustic with quicklime, in order to
dissolve the albuminous matter coagulated by the heat, and give complete
fluidity to the mass. The alkali also neutralises the tartaric acid
present. The mashed matter must now be mixed with the crushed malt
diffused through 40 or 50 pounds of cold water for every 100 pounds of
potatos, which lowers the temperature to 167°. The wort must be then
diligently stirred during two hours; mixed with 40 or 50 pounds of cold
water for 100 pounds of potatos, and when reduced to the temperature of
77° put into the fermenting tun along with the proper quantity (3 or 4
per cent.) of yeast. As potatos readily pass into the acetous
fermentation, the admixture of the malt, the mashing, and the cooling
should be rapidly performed, while the utmost cleanliness must be
observed.
The fermentation is brisk, probably from the agency of the albumen, and
furnishes a good head of barm, which answers well for the bakers; 100
pounds of potatos yield from 18 to 20 pounds measure of spirits, nine
elevenths of our excise proof; or about 16 pounds measure of proof, =
about 1-2/3 gallons.
It has been observed that after the month of December potatos begin to
yield a smaller product of fermented spirits; and when they have once
sprouted or germinated, they afford very little indeed. From the
difficulty of keeping and transporting potatos, distillation from them,
even though our laws now permit it, can never become general till some
plan be adopted for overcoming these disadvantages. A scheme of this
kind, however, has been successfully practised in Vienna, which consists
in subjecting the washed potatos to strong pressure in a perforated
chest by a hydraulic or screw press, whereby they lose about three
fourths of their weight, and may then be readily dried into a white
flour, that may be kept for several years without injury, and
transported to considerable distances with comparative ease. This flour,
mixed with a moderate quantity of ground malt, and saccharified by
mashing with water, at the temperature of 167° F., becomes capable of
affording a sweet wort convertible by fermentation either into beer or
whiskey.
Horse-chestnuts, according to Hermstaedt, are an eligible material for
producing alcohol, as 128 pounds of them afford 100 pounds of meal;
which 100 pounds yield, by proper treatment, 34 pounds of spirits,
containing 36 per cent. of absolute alcohol, by Richter’s tables. Barley
to the extent of 10 pounds per 100 should be ground up with them, after
they have been boiled in a steam apparatus, not only for the purpose of
softening them, but freeing them from their bitter astringent matter.
Acorns are productive of alcohol by similar treatment.
The best means hitherto discovered for depriving bad whiskey of its
nauseous smell and taste, is to pass it through well-burned and coarsely
pulverised charcoal, distributed as follows in a series of cylindrical
casks. Each vessel must have a double bottom, the false one being
perforated with conical holes, and placed a few inches above the true.
Upon this perforated board a layer of chopped clean straw one inch thick
is laid; and over the straw, a stratum of small river gravel, the size
of large peas. This is to be covered with a pretty thick stratum of the
charcoal, previously freed from dirt and dust by washing; upon which a
piece of close canvass is to be spread, and pressed down by a thin bed
of river sand. The cylinder or cask should be filled with these
successive layers to within two inches of its top, and it is then to be
closed air-tight. Immediately below the head, a round orifice is pierced
in the side, for receiving an overflow tube, which is either screwed
rectangularly to another elbow pipe, or is bent (when of block tin) so
as to enter tight into an orifice beneath the false bottom of the second
cylinder or cask. In this way, the series may be continued to any
desired number of vessels; the last discharging the purified spirit into
the store-back. The foul spirit must be made to flow into the bottom
space of the first cylinder down through a pipe in communication with a
charging-back placed upon such an elevated level as to give sufficient
pressure to force the spirits up through the series of filters; the
supply-pipe being provided with a regulating stop-cock. The spirit may
be filtered _downwards_ through sand and cloth in its final passage to
the receiver. It has been found, with very crude spirits, that eight
successive cylinders were required to deprive them entirely of the rank
flavour.
In the year 1831, 23,000,000 gallons of spirits were made in the United
Kingdom, equivalent to the consumption of 1,500,000 quarters of grain,
and for that year and the four preceding years, there were imported
annually 2,000,000 of quarters of foreign barley.
In 1832, 20,778,521 gallons paid excise duty.
1834, 23,397,806.
1836, 27,137,000; of which 14,000,000 were Irish.
We may add to the last quantity, 3 millions of gallons at least on the
score of smuggling, in licensed and illicit distilleries; making 30
millions to be the frightful amount of whiskey consumed by the British
people, independent of other intoxicating liquors.
DOCIMACY, from the Greek Δοκιμαζω, I prove; (_Docimasie_, Fr.;
_Probierkunst_, Germ.;) is the art by which the nature and proportions
of an ore are determined. This analytical examination was originally
conducted in the dry way, the metal being extracted from its
mineralizers, by means of heat and certain fluxes. But this method was
eventually found to be insufficient and even fallacious, especially when
volatile metals were in question, or when the fluxes could absorb them.
The latter circumstance became a very serious evil, whenever the object
was to appreciate an ore that was to be worked at great expense.
Bergmann first demonstrated, in an elaborate dissertation, that the
humid analysis was much to be preferred; and since his time the dry way
has been consecrated chiefly to the direction of metallurgic operations,
or, at least, it has been employed merely in concert with the humid, in
trials upon the small scale.
After discovering an ore of some valuable metal, it is essential to
ascertain if its quantity and state of combination will justify an
adventurer in working the mine, and smelting its products. The metal is
rarely found in a condition approaching to purity; it is often
disseminated in a mineralizing _gangue_ far more bulky than itself; and
more frequently still it is combined with simple non-metallic
substances, such as sulphur, carbon, chlorine, oxygen, and acids, more
or less difficult to get rid of. In these compound states its
distinctive characters are so altered, that it is not an easy task
either to recognize its nature, or to decide if it can be smelted with
advantage. The assayer, without neglecting any of the external
characters of the ore, seeks to penetrate, so to speak, into its
interior; he triturates it to an impalpable powder, and then subjects it
to the decomposing action of powerful chemical reagents; sometimes with
the aid of alkalies or salts appropriate to its nature, he employs the
dry way by fire alone; at others, he calls in the solvent power of acids
with a digesting heat; happy, if after a series of labours, long,
varied, and intricate, he shall finally succeed in separating a notable
proportion of one or more metals either in a pure state, or in a form of
combination such, that from the amount of this known compound, he can
infer, with precision, the quantity of fine metal, and thereby the
probable value of the mine. The blow-pipe, skilfully applied, affords
ready indications of the nature of the metallic constituents, and is
therefore usually the preliminary test. The separation of the several
constituents of the ore can be effected, however, only by a chemist, who
joins to the most extensive knowledge of the habitudes of mineral
substances, much experience, sagacity, and precision, in the conduct of
analytical operations. Under the individual metals, as also in the
articles METALLURGY, MINES, and ORES, I have endeavoured to present such
a copious and correct detail of docimastic processes, as will serve to
guide the intelligent student through this most mysterious labyrinth of
nature and art.
DORNOCK, is a species of figured linen of stout fabric, which derives
its name from a town in Scotland, where it was first manufactured for
table-cloths. It is the most simple in pattern of all the varieties of
the diaper or damask style, and therefore the goods are usually of
coarse quality for common household wear. It receives the figure by
reversing the flushing of the warp and woof at certain intervals, so as
to form squares, or oblong rectangles upon the cloth. The most simple of
these is a succession of alternate squares, forming an imitation of a
checker board or mosaic work. The coarsest kinds are generally woven as
tweels of three leaves, where every thread floats over two, and is
intersected by the third in succession. Some of the finer are tweels of
four or five leaves, but few of more; for the six and seven leaf tweels
are seldom or never used, and the eight leaf tweel is confined almost
exclusively to damask. See TEXTILE FABRIC.
DRAGON’S BLOOD; (_Sang dracon_, Fr.; _Drachenblut_, Germ.) is a resinous
substance, which comes to us sometimes in small balls of the size of a
pigeon’s egg, sometimes in rods, like the finger, and sometimes in
irregular cakes. Its colour, in lump, is dark brown red; in powder,
bright red; friable; of a shining fracture, sp. grav. 1·196. It contains
a little benzoic acid, is insoluble in water, but dissolves readily in
alcohol, ether, and oils. It is brought from the East Indies, Africa,
South America, as the produce of several trees, the _Dracæna Draco_, the
_Pterocarpus santalinus_, the _Pterocarpus Draco_, and the _Calamus
Rotang_.
Dragon’s blood is used chiefly for tingeing spirit and turpentine
varnishes, for preparing gold lacquer, for tooth tinctures and powders,
for staining marble, &c. According to Herbenger, it consists of 9·07
parts of red resin, 2 of fat oil, 3 of benzoic acid, 1·6 of oxalate, and
3·7 of phosphate of lime.
DRUGGET, is a coarse, but rather slight, woollen fabric, used for
covering carpets, and as an article of clothing by females of the poorer
classes. It is now-a-days nearly superseded by coarse cotton goods.
[Illustration: 363]
DRYING HOUSE. An apartment fitted up in a peculiar manner for drying
calicoes, and other textile fabrics. Mr. Southworth, of Sharples, a
Lancashire bleacher, obtained a patent, in 1823, for the following
ingenious arrangement, which has been since generally adopted, with
certain modifications, in most of our extensive bleaching and printing
works. _Fig._ 363. is a section of the drying-house, where _a_ is a
furnace and boiler for the purpose of generating steam; it is furnished
with a safety valve in the tube _b_, at top, and from this tube the
steam main _c_ passes down to the floor of the basement story. From this
main, a series of steam-pipes, as _d d_, extend over the surface of the
floor, and from them heat is intended to be diffused for the purpose of
warming the drying-house.
Along the middle of the building a strong beam of timber _e e_, extends,
and is supported by cast-iron pillars; from this beam, to bearings on
the side walls, a series of rails are carried in a cross direction, over
which rails the wet cloth is to be hung in folds, and the steam or
evaporation emitted in drying is allowed to escape through apertures or
ventilators in the roof.
The mode in which the cloth is delivered on to the rails, on either side
of the beam, will be best understood by reference to the delivering
carriage, which is shown, with its rollers partly in section.
The wet cloth is first to be coiled upon a roller, and then placed in
the carriage, as at _f_, with its pivots bearing upon inclined planes.
The carriage is to be placed at the commencement of the rails, running
upon the middle beam, and also upon the side-bearings or railways
extending along the side walls of the building, parallel to and upon a
level with the same beam. It is made to travel by means of an endless
band passing over two riggers, _g_ and _h_, in _fig._ 363., and over
pulleys and a band-wheel attached to the carriage, as will be explained.
The rigger _g_, which moves this endless band, is actuated by bevel
geer, seen at _i_, which is put in motion by a pinion at the end of a
revolving shaft leading from a steam engine.
In the same _fig._, _k k_ is the endless band passing over a pulley
under the band-wheel, and over the pulley _n_, by which it will be
perceived that the traversing of the band, as described, would cause
these pulleys and wheels to revolve. On the axle of the band-wheel _m_,
there is a drum against which the roll of wet cloth _f_ presses, and as
this drum revolves, the roll of wet cloth is, by its friction, made to
turn in a contrary direction, and to deliver off the cloth on to the
periphery of the drum, whence it passes over a roller and descends to
the tails. Upon the end of the axle of the band-wheel _m_, there is a
pinion which takes into the teeth of the large wheel, and upon the axle
of this large wheel there is a pinion that actuates the intermediate
wheel, which turns another toothed wheel. This last-mentioned toothed
wheel takes into cogs upon the side railway, and hence, as the train of
wheels moves round, the carriage to which the wheels are attached is
slowly impelled forward.
As soon as the wheels begin to move, and the carriage to advance, the
wet cloth begins to uncoil, and to pass down over the first roller; a
small roller attached to the carriage, as it passes over the rails in
succession, holds the cloth against each rail for a short space of time,
and prevents it from slipping, by which means the cloth descends in
folds or loops between the rails, and is thereby made to hang in a
series of folds or loops, as shown in the figure.
It will be perceived that as the pivots of the cloth roller _f_ bear
upon inclined planes, the roller will continually slide down as the
cloth diminishes in bulk, keeping in contact with the drum, and
delivering the cloth from the roller on to the several rails, as
described.
In order to stop the carriage in any part of its course, or to adjust
any of the folds of the cloth, a man is usually placed upon the platform
travelling with the carriage, over which he has perfect command. This
apparatus may be also employed for taking the cloth when dried off the
rails; in which case the carriage must be made to travel backwards, and
by first guiding the end of the cloth on to the roller _f_, and then
putting the wheels in a retrograde motion, the cloth will be
progressively coiled upon the roller _f_, in a similar way to that by
which it was uncoiled.
DUCTILITY, (_Streckbarkeit_, Germ.) is the property of being drawn out
in length without breaking, possessed in a pre-eminent degree by gold
and silver, as also by many other metals, by glass in the liquid state,
and by many semifluid resinous and gummy substances. The spider and the
silk-worm exhibit the finest natural exercise of ductility upon the
peculiar viscid secretions from which they spin their threads. When a
body can be readily extended in all directions under the hammer, it is
said to be malleable, and when into fillets under the rolling press, it
is said to be laminable.
_Table of the ductility and malleability of Metals._
+-------------------+---------------+--------------+--------------+
| Metals ductile |Brittle metals | Metals in the|Metals in the |
| and malleable in |in alphabetical|order of their|order of their|
|alphabetical order.| order. | wire-drawing | laminable |
| | | ductility. | ductility. |
+-------------------+---------------+--------------+--------------+
| Cadmium. | Antimony. | Gold. | Gold. |
| Copper. | Arsenic. | Silver. | Silver. |
| Gold. | Bismuth. | Platinum. | Copper. |
| Iron. | Cerium. ? | Iron. | Tin. |
| Iridium. | Chromium. | Copper. | Platinum. |
| Lead. | Cobalt. | Zinc. | Lead. |
| Magnesium. | Columbium. ? | Tin. | Zinc. |
| Mercury. | Iridium. | Lead. | Iron. |
| Nickel. | Manganese. | Nickel. | Nickel. |
| Osmium. | Molybdenum. | Palladium. ?| Palladium. ?|
| Palladium. | Osmium. | Cadmium. ? | Cadmium. ? |
| Platinum. | Rhodium. | | |
| Potassium. | Tellurium. | | |
| Silver. | Titanium. | | |
| Sodium. | Tungsten. | | |
| Tin. | Uranium. | | |
| Zinc. | | | |
+-------------------+---------------+--------------+--------------+
There appears to be therefore a real difference between ductility and
malleability; for the metals which draw into the finest wire are not
those which afford the thinnest leaves under the hammer or in the
rolling press. Of this fact iron affords a good illustration. Among the
metals permanent in the air, 17 are ductile and 16 are brittle. But the
most ductile cannot be wire-drawn or laminated to any considerable
extent without being annealed from time to time during the progress of
the extension, or rather, the sliding of the particles alongside of each
other, so as to loosen their lateral cohesion.
DUNGING, in calico-printing, is the application of a bath of cowdung,
diffused through hot water, to cotton goods in a particular stage of the
manufacture. Dunging and scouring are commonly alternated, and are two
of the most important steps in the process. The operation of dunging has
for its objects:--
1. To determine the entire combination of the aluminous sub-salts with
the stuffs, by separating almost all the acetic acid which was not
volatilized in the stove-drying of the mordant.
2. To dissolve and carry off from the cloth a portion of the thickening
matters.
3. To separate from the cloth the part of the mordant that is
uncombined, and merely mixed mechanically with the gum or starch.
4. To prevent, by the peculiar action of the dung, the uncombined
mordant, as well as the acetic acid with which the bath is apt to get
loaded, from affecting the blank parts of the cloth, or being injurious
to the mordant.
The aluminous base or mordant on the cloth, more or less neutralized by
the dunging, is next subjected to the dash-wheel or fulling mill, where
by the stream of water the remainder of the thickening and other
impurities are washed away.
No very exact analysis has been made of cowdung. Morin’s, which is the
most recent and elaborate, is as follows:--
Water 70·00
Vegetable fibre 24·08
Green resin and fat acids 1·52
Undecomposed biliary matter 0·60
Peculiar extractive matter (_bubuline_) 1·60
Albumen 0·40
Biliary resin 1·80
According to M. Kœchlin’s practical knowledge on the great scale, it
consists of a moist fibrous vegetable substance, which is animalized,
and forms about one-tenth of its weight; 2. of albumen; 3. of animal
mucus; 4. of a substance similar to bile; 5. of muriate of soda, muriate
and acetate of ammonia, phosphate of lime and other salts; 6. of benzoin
or musk.
Probably the hot water in which the calico-printer diffuses the dung,
exerts a powerful solvent action, and in proportion as the uncombined
mordant floats in the bath it is precipitated by the albumen, the animal
mucus, and the ammoniacal salts; but there is reason to think that the
fibrous matter in part animalized or covered with animal matter, plays
here the principal part; for the great affinity of this substance for
the aluminous salts is well known.
All practical men are aware that the affinity of cotton for alumina is
increased by its combination with oil or animal substances, to such a
degree as to take it from the dung bath; which would not be possible
without this combination. It would therefore appear that the principal
function of dunging is to hinder the uncombined mordant, diffused in the
dung bath, from attaching itself to the unmordanted portion of the
cloth, as already observed; for if we merely wished to abstract the
thickening stuffs, or to complete by the removal of acetic acid the
combination of the aluminous base with the goods, dung would not be
required, for hot water would suffice. In fact, we may observe, that in
such cases the first pieces passed through the boiler are fit for
dyeing; but when a certain number have been passed through, the mordant
now dissolved in the water is attracted to the white portions of the
cloth, while the free acid impoverishes the mordanted parts, so that
they cannot afford good dyes, and the blank spaces are tarnished.
The cow dung may be in some measure replaced by bran, but not with
perfect success. The former both answers the purpose better and is
cheaper. The bran is only preferred for the most delicate yellows, for
cochineal pinks and lilacs, to which the dung may sometimes impart a
greenish cast. It is to be presumed that the action of the bran in this
process has much analogy with that of the dung, and that the ligneous
fibre is the most active constituent; with which the gluten and mucilage
co-operate, no doubt, in seizing the aluminous salts.
It seems to be ascertained that the mordant applied to the cloth does
not combine entirely with it during the drying; that this combination is
more or less perfect according to the strength of the mordants, and the
circumstances of the drying; that the operation of dunging, or passing
through hot water, completes the combination of the cloth with the
aluminous base now insoluble in water; that this base may still contain
a very minute quantity of acetic acid or sulphate of alumina; that a
long ebullition in water impoverishes the mordant but a little; and that
even then the liquid does not contain any perceptible quantity of
acetate or subsulphate of alumina.
The manner of immersing the goods, or passing them through the dung
bath, is an important circumstance. They should be properly extended and
free from folds, which is secured by a series of cylinders.
The cistern is from 10 to 12 feet long, 4-1/2 feet wide, and 6 or 8 feet
deep. The piece passes alternately over the upper rollers and under
rollers near the bottom. There are two main squeezing rollers at one
end, which draw the cloth through between them. Whenever the goods come
out of the bath they are put into the dash-wheel. The immersion should
take place as fast as possible, for the moment the hot water penetrates
the mordanted cloth, the acetic acid quits it; and, therefore, if the
immersion was made slowly or one ply after another, the acid as well as
the uncombined mordant become free, would spread their influence, and
would have time to dissolve the aluminous subsalts now combined with the
cloth; whence inequalities and impoverishment of the colours would
ensue.
It is difficult to determine the number of pieces which may be passed
through a given quantity of dung and water. This depends upon the state
of the mordants, whether they are strong or acid, and on the quantity of
the surface covered with the figures. The number varies usually from 20
to 60 pieces, for from 240 to 300 gallons of water and 6 gallons of
dung. The time of the immersion varies with the concentration of the
mordants, and the nature of their thickening. The temperature must be
regulated by the same circumstances; for starch or flour paste a much
warmer bath is needed than for gum. The heat varies usually from 130° to
212° F. When the printing is heavy and the thickening is starch or
flour, the goods are usually twice dunged, with two washings between the
two dungs. A strong acid mordant is more difficult to dung and to wash
than a neutral mordant, especially when it is to receive the madder dye.
Sometimes a little chalk is added to the bath, when the goods have been
padded in an acid mordant. Too much dung is injurious to weak mordants,
as well as to pinks. It has also been remarked that a mordant when
neutralized does not produce as brilliant tints, especially yellows. The
latter are obtained of a finer shade when, instead of dunging, they are
exposed for an hour in a stream of water, provided its temperature is
not too low. In winter they are passed through a slightly chalky water,
then washed at the wheel, and dyed in quercitron or weld.
A very able and learned memoir upon this subject, by M. Penot, Professor
of Chemistry, appeared in the Bulletin of the Society of Mulhausen, in
October, 1834, with an ingenious commentary upon it, under the title of
a Report by M. Camille Kœchlin, in March, 1835.
Experience has proved that dunging is one of the most important steps in
the process of calico printing, and that if it be not well performed the
dyeing is good for nothing. Before we can assign its peculiar function
to the dung in this case, we must know its composition. Fresh cow’s dung
is commonly neutral when tested by litmus paper; but sometimes it is
slightly alkaline, owing, probably, to some peculiarity in the food of
the animal.
The total constituents of 100 parts of cow dung are as follows: Water,
69·58; bitter matter, 0·74; sweet substance, 0·93; chlorophylle, 0·28;
albumine, 0·63; muriate of soda, 0·08; sulphate of potash, 0·05;
sulphate of lime, 0·25; carbonate of lime, 0·24; phosphate of lime,
0·46; carbonate of iron, 0·09; woody fibre, 26·39; silica, 0·14; loss,
0·14.
In dunging calicoes the excess of uncombined mordant is in part
attracted by the soluble matters of the cow’s dung, and forms an
insoluble precipitate, which has no affinity for the cloth, especially
in presence of the insoluble part of the dung, which strongly attracts
alumina. The most important part which that insoluble matter plays, is
to seize the excess of the mordants, in proportion as they are dissolved
by the water of the bath, and thus to render their reaction upon the
cloth impossible. It is only in the deposit, therefore, that the matters
carried off from the cloth by the dung are to be found.
M. Camille Kœchlin ascribes the action of cow dung chiefly to its
albuminous constituent, combining with the alumina and iron, of the
acetates of these bases dissolved by the hot water of the bath. The
acids consequently set free, soon become evident by the test of litmus
paper, after a few pieces are passed through, and require to be got rid
of either by a fresh bath or by adding chalk to the old one. The dung
thus serves also to fix the bases on the cloth, when used in moderation.
It exercises likewise a disoxidating power on the iron mordant, and
restores it to a state more fit to combine with colouring matter.
DYEING, (_Teinture_, Fr.; _Färberei_, Germ.) is the art of impregnating
wool, silk, cotton, linen, hair, and skins, with colours not removable
by washing, or the ordinary usage to which these fibrous bodies are
exposed when worked up into articles of furniture or raiment. I shall
here consider the general principles of the art, referring for the
particular dyes, and peculiar treatment of the stuffs to be dyed, to the
different tinctorial substances in their alphabetical places; such as
cochineal, indigo, madder, &c.
Dyeing is altogether a chemical process, and requires for its due
explanation and practice an acquaintance with the properties of the
elementary bodies, and the laws which regulate their combinations. It is
true that many operations of this, as of other chemical arts, have been
practised from the most antient times, long before any just views were
entertained of the nature of the changes that took place. Mankind,
equally in the rudest and most refined state, have always sought to
gratify the love of distinction by staining their dress sometimes even
their skin, with gaudy colours. Moses speaks of raiment dyed blue, and
purple, and scarlet, and of sheep-skins dyed red; circumstances which
indicate no small degree of tinctorial skill. He enjoins purple stuffs
for the works of the tabernacle and the vestments of the high priest.
In the article CALICO PRINTING, I have shown from Pliny that the antient
Egyptians cultivated that art with some degree of scientific precision,
since they knew the use of mordants, or those substances which, though
they may impart no colour themselves, yet enable white robes (_candida
vela_) to absorb colouring drugs (_colorem sorbendibus medicamentis_).
Tyre, however, was the nation of antiquity which made dyeing its chief
occupation and the staple of its commerce. There is little doubt that
purple, the sacred symbol of royal and sacerdotal dignity, was a colour
discovered in that city, and that it contributed to its opulence and
grandeur. Homer marks no less the value than the antiquity of this dye,
by describing his heroes as arrayed in purple robes. Purple habits are
mentioned among the presents made to Gideon by the Israelites from the
spoils of the kings of Midian.
The juice employed for communicating this dye was obtained from two
different kinds of shell-fish, described by Pliny under the names of
_purpura_ and _buccinum_; and was extracted from a small vessel, or sac,
in their throats, to the amount of only one drop from each animal. A
darker and inferior colour was also procured by crushing the whole
substance of the buccinum. A certain quantity of the juice collected
from a vast number of shells being treated with sea-salt, was allowed to
ripen for three days; after which it was diluted with five times its
bulk of water, kept at a moderate heat for six days more, occasionally
skimmed to separate the animal membranes, and when thus clarified was
applied directly as a dye to white wool, previously prepared for this
purpose by the action of lime-water, or of a species of lichen called
fucus. Two operations were requisite to communicate the finest Tyrian
purple; the first consisted in plunging the wool into the juice of the
purpura; the second, into that of the buccinum. Fifty drachms of wool
required one hundred of the former liquor, and two hundred of the
latter. Sometimes a preliminary tint was given with coccus, the kermes
of the present day, and the cloth received merely a finish from the
precious animal juice. The colours, though probably not nearly so
brilliant as those producible by our cochineal, seem to have been very
durable, for Plutarch says, in his _Life of Alexander_, (chap. 36.),
that the Greeks found in the treasury of the king of Persia a large
quantity of purple cloth, which was as beautiful as at first, though it
was 190 years old.[26]
[26] ‘Among other things, there was purple of Hermione (?) to the
amount of five thousand talents.’ (Plutarch’s Lives, translated by
Langhorne, Wrangham’s edition, vol. v. p. 240.) Horace celebrates the
Laconian dye in the following lines:--
Nec Laconicas mihi
Trahunt honestæ purpuras clientæ.
(Carm., lib. ii., Ode 18.)
The difficulty of collecting the purple juice, and the tedious
complication of the dyeing process, made the purple wool of Tyre so
expensive at Rome that in the time of Augustus a pound of it cost nearly
30_l._ of our money.[27] Notwithstanding this enormous price, such was
the wealth accumulated in that capital, that many of its leading
citizens decorated themselves in purple attire, till the emperors
arrogated to themselves the privilege of wearing purple, and prohibited
its use to every other person. This prohibition operated so much to
discourage this curious art as eventually to occasion its extinction,
first in the western and then in the eastern empire, where, however, it
existed in certain imperial manufactories till the eleventh century.
[27] Pliny says that a pound of the double-dipped Tyrian purple was
sold in Rome for a hundred crowns.
Dyeing was little cultivated in antient Greece; the people of Athens
wore generally woollen dresses of the natural colour. But the Romans
must have bestowed some pains upon this art. In the games of the circus
parties were distinguished by colours. Four of these are described by
Pliny, the green, the orange, the grey, and the white. The following
ingredients were used by their dyers. A crude native alum mixed with
copperas, copperas itself, blue vitriol, alkanet, lichen rocellus, or
archil, broom, madder, woad, nut-galls, the seeds of pomegranate, and of
an Egyptian acacia.
Gage, Cole, Plumier, Reaumur, and Duhamel have severally made researches
concerning the colouring juices of shell-fish caught on various shores
of the ocean, and have succeeded in forming a purple dye, but they found
it much inferior to that furnished by other means. The juice of the
buccinum is at first white; it becomes by exposure to air of a yellowish
green bordering on blue; it afterwards reddens, and finally changes to a
deep purple of considerable vivacity. These circumstances coincide with
the minute description of the manner of catching the purple-dye
shell-fish which we possess in the work of an eye-witness, Eudocia
Macrembolitissa, daughter of the Emperor Constantine VIII., who lived in
the eleventh century.
The moderns have obtained from the New World several dye-drugs unknown
to the antients; such as cochineal, quercitron, Brazil wood, logwood,
annatto; and they have discovered the art of using indigo as a dye,
which the Romans knew only as a pigment. But the vast superiority of our
dyes over those of former times must be ascribed principally to the
employment of pure alum and solution of tin as mordants, either alone or
mixed with other bases; substances which give to our common dye-stuffs
remarkable depth, durability, and lustre. Another improvement in dyeing
of more recent date is the application to textile substances of metallic
compounds, such as Prussian blue, chrome yellow, manganese brown, &c.
Indigo, the innoxious and beautiful product of an interesting tribe of
tropical plants, which is adapted to form the most useful and
substantial of all dyes, was actually denounced as a dangerous drug, and
forbidden to be used, by our parliament in the reign of Queen Elizabeth.
An act was passed authorizing searchers to burn both it and logwood in
every dye-house where they could be found. This act remained in full
force till the time of Charles II.; that is, for a great part of a
century. A foreigner might have supposed that the legislators of England
entertained such an affection for their native woad, with which their
naked sires used to dye their skins in the old times, that they would
allow no outlandish drug to come in competition with it. A most
instructive book might be written illustrative of the evils inflicted
upon arts, manufactures, and commerce, in consequence of the ignorance
of the legislature.[28]
[28] Author, in Penny Cyclopedia.
Colours are not, properly speaking, material; they are impressions which
we receive from the rays of light reflected, in a decomposed state, by
the surfaces of bodies. It is well known that a white sunbeam consists
of an indeterminate number of differently coloured rays, which being
separated by the refractive force of a glass prism, form the solar
spectrum, an image distinguishable into seven sorts of rays; the red,
orange, yellow, green, blue, indigo, and violet. Hence, when an opaque
body appears coloured, for example, red, we say that it reflects the red
rays only, or in greatest abundance, mixed with more or less of the
white beam, which has escaped decomposition. According to this manner of
viewing the colouring principle, the art of dyeing consists in fixing
upon stuffs, by means of corpuscular attraction, substances which act
upon light in a different manner from the surfaces of the stuffs
themselves. The dyer ought, therefore, to be familiar with two
principles of optics; the first relative to the mixture of colours, and
the second to their simultaneous contrast.
Whenever the different coloured rays, which have been separated by the
prism, are totally reunited, they reproduce white light. It is evident,
that in this composition of light, if some rays were left out, or if the
coloured rays be not in a certain proportion, we should not have white
light, but light of a certain colour. For example; if we separate the
red rays from the light decomposed by a prism, the remaining coloured
rays will form by their combination a peculiar bluish green. If we
separate in like manner the orange rays, the remaining coloured rays
will form by their combination a blue colour. If we separate from the
decomposed prismatic light the rays of greenish yellow, the remaining
coloured rays will form a violet. And if we separate the rays of yellow
bordering on orange, the remaining coloured rays will form by their
union an indigo colour.
Thus we see that every coloured light has such a relation with another
coloured light that, by uniting the first with the second, we reproduce
white light; a relation which we express by saying that the one is the
complement of the other. In this sense, red is the complementary colour
of bluish green; orange, of blue; greenish yellow, of violet; and orange
yellow, of indigo. If we mix the yellow ray with the red, we produce
orange; the blue ray with the yellow, we produce green; and the blue
with the red, we produce violet or indigo, according as there is more or
less red relatively to the blue. But these tints are distinguishable
from the orange, green, indigo, and violet of the solar spectrum,
because when viewed through the prism they are reduced to their
elementary component colours.
If the dyer tries to realize the preceding results by the mixture of
dyes, he will succeed only with a certain number of them. Thus, with red
and yellow he can make orange; with blue and yellow, green; with blue
and red, indigo or violet. These facts, the results of practice, have
led him to conclude that there are only three primitive colours; the
red, yellow, and blue. If he attempts to make a white, by applying red,
yellow, and blue dyes in certain quantities to a white stuff, in
imitation of the philosopher’s experiment on the synthesis of the
sunbeam, far from succeeding, he will deviate still further from his
purpose, since the stuff will by these dyes become so dark coloured, as
to appear black.
This fact must not, however, lead us to suppose that in every case where
red, yellow, and blue are applied to white cloth, black is produced. In
reality, when a little ultramarine, cobalt blue, Prussian blue, or
indigo, is applied to goods with the view of giving them the best
possible white, if only a certain proportion be used, the goods will
appear whiter after this addition than before it. What happens in this
case? The violet blue forms, with the brown yellow of the goods, a
mixture tending to white, or less coloured than the yellow of the goods
and the blue together were. For the same reason, a mixture of prussian
blue and cochineal pink has been of late years used in the whitening or
the azuring of silks, in preference to a pure blue; for on examining
closely the colour of the silk to be neutralized, it was found by the
relations of the complementary colours, that the violet was more
suitable than the indigo blue formerly used. The dyer should know, that
when he applies several different colouring matters to stuffs, as yellow
and blue, for example, if they appear green, it is because the eye
cannot distinguish the points which reflect the yellow from those which
reflect the blue; and that, consequently, it is only where the
distinction is not possible, that a mixture or combination appears. When
we examine certain gray substances, such as hairs, feathers, &c., with
the microscope, we see that the gray colour results from black points,
disseminated over a colourless or slightly coloured surface. In
reference to compound colours, this instrument might be used with
advantage by the dyer.
The dyer should be acquainted also with the law of the simultaneous
contrast of colours. When the eye views two colours close alongside of
each other, it sees them differing most in their optical composition,
and in the height of their tone, when the two are not equally pale or
full-bodied. They appear most different as to their optical composition,
when the complementary of the one of them is added to the colour of the
other. Thus, put a green zone alongside of an orange zone; the red
colour complementary of green, being added to the orange, will make it
appear redder; and in like manner the blue, complementary of orange,
being added to the green, will make it appear more intensely blue. In
order to appreciate these differences, let us take two green stripes and
two orange stripes, placing one of the green stripes near one of the
orange; then place the two others so that the green stripe may be at a
distance from the other green stripe, but on the same side, and the
orange at a distance from the other orange, also on the same side.
As to the contrast in the height of the tone, we may satisfy ourselves
by taking the tones No. 1. No. 2. No. 15. and No. 16. from a graduated
pallet of reds: for example, by placing No. 2. and No. 15. close
alongside, putting No. 1. at a distance from No. 2. on the same side,
and No. 16. at a distance from No. 15. on the same side,--we shall see
(if the pallet is sufficiently lowered in tone) No. 2. equal to No. 1.,
and No. 15. equal to No. 16.; whence it follows that No. 2., by the
vicinity of No. 15., will appear to have lost some of its colour; while
No. 15. will appear to have acquired colour. When black or gray figures
are printed upon coloured grounds, these figures are of the colour
complementary of the ground. Consequently, in order to judge of their
colour, we must cut out spaces in a piece of gray or white paper, so as
to allow the eye to see nothing but the figures; and if we wish to
compare figures of the same colour, applied upon grounds of different
colours, we can judge rightly of the figures only by insulating them
from the grounds.
The relations of dyeing with the principles of chemistry, constitute the
theory of the art, properly speaking; this theory has for its basis, the
knowledge--1. of the species of bodies which dyeing processes bring into
contact; 2. of the circumstances in which these species act; 3. of the
phenomena which appear during their action; and 4. of the properties of
the coloured combinations which are produced. These generalities may be
specified under the ten following heads:--
1. The preparation of the stuffs to be dyed, whether fibres, yarn, or
cloth; under the heads of ligneous matter, cotton, hemp, flax; and of
the animal matters, silk and wool.