An empty crucible, called a _caster_ (_giesser_), is taken out of the
furnace through the crown with a pair of tongs, and is kept red hot by
placing it in a hollow hearth (_mundal_), surrounded with burning coals;
into this crucible the contents of four of the melting pots are poured;
the dross being raked out with an iron scraper. As soon as the melting
pot is emptied, it is immediately re-charged in the manner above
described, and replaced in the furnace. The surface of the melted brass
in the _caster_ is swept with the stump of a broom, then stirred about
with the iron rake, to bring up any light foreign matter to the surface,
which is then skimmed with a little scraper; the crucible is now seized
with the casting tongs, and emptied in the following way:--
[Illustration: 164 165]
The mould or _form_ for casting sheet brass consists of two slabs of
granite, _a a_, _figs._ 164, 165. They are 5-1/2 feet long; 3 feet
broad, 1 foot thick, and, for greater security, girt with iron bands, _b
b_, 2 inches broad, 1-1/2 thick, and joined at the four corners with
bolts and nuts. The mould rests upon an oaken block, _c_, 3-1/2 feet
long, 2-1/6 broad, and 1-1/4 thick, which is suspended at each end upon
gudgeons, in bearing blocks, placed under the foundery floor, _d d_, in
the casting pit, _e e_. This is lined with bricks; and is 6-3/4 feet
long, 5-1/2 broad, and 2 deep; upon the two long side walls of the pit,
the bearing blocks are laid, which support the gudgeons. The
swing-blocks are 10 inches long, 18 inches broad, 15 inches thick, and
are somewhat rounded upon their back edge, so that the casting frame may
slope a little to the horizon. To these blocks two cross wooden arms, _f
f_, are mortised, upon which the under slab rests, freely, but so as to
project about 5 inches backwards over the block, to secure an equipoise
in the act of casting. _g g_ are bars, placed at both of the long sides,
and one of the ends, between the slabs, to determine the thickness of
the brass-plate. Upon the other slab the gate _h_ is fastened, a sheet
of iron 6 inches broad, which has nearly the shape of a parallel
trapezium (lozenge), and slopes a little towards the horizon. It serves
for setting the casting pot upon in the act of pouring out, and renders
its emptying more convenient. That gate (_steinmaul_) is coated with a
mixture of loam and hair. The upper slab is secured to the under one in
its slanting position by an _armour_ or binding. This consists of the
tension bars of wood, _i k l m_, of the iron bars _n_, (3 to 3-1/2
inches broad, 1-1/2 inch thick, see the top view, _fig._ 165.) of a rod
with holes and pins at its upper end, and of the iron screw spindle _o_.
The mode in which these parts act may be understood from inspection of
the figure. In order to lift the upper slab from the under one, which is
effected by turning it round its edge, a chain is employed, suspending
two others, connected with the slab. The former passes over a pulley,
and may be pulled up and down by means of a wheel and axle, or with the
aid of a counterweight. Upon each of the two long sides of the slab
there are two iron rings, to which the ends of the chains may be hooked.
The casting faces of the slab must be coated with a layer of finely
ground loam; the thinner the better.
When calamine is employed, 1/2 cwt. of copper, 3/4 cwt. of calamine, and
1/3 the volume of both of charcoal mixed, are put into 7 crucibles, and
exposed to heat during 11 or 12 hours; the product being from 70 to 72
lbs. of brass.
_Brass-plate rolling._--At Hegermühl there are two re-heating or
annealing furnaces, one larger, 18 feet long, and another smaller,
8-1/2; the hot chamber is separated from the fire place by iron beams,
in such a way that the brass castings are played upon by the flames on
both their sides. After each passage through the laminating press
(rolls) they are heated anew, then cooled and laminated afresh, till
they have reached the proper length. The plates are besmeared with
grease before rolling.
[Illustration: 166 167 168]
_Fig._ 166. shows the ground plan of the furnace and its railway; _fig._
167. the cross section; and _fig._ 168. the section lengthwise; _a a_,
the iron way bars or rails upon the floor of the foundry, for enabling
the wheels of the waggon-frame to move readily backwards and forwards;
_b b_, the two grates; _c c_, the ash pits; _d d_, the fire beams; _e e
e_, vents in the roof of the hot chamber _f_; _g g_, two plates for
shutting the hot chamber; _h_, the flue; _i_, the chimney. After the
rolling, the sheets covered with a black oxide of copper, are plunged
into a mother water of the alum works for a few minutes, then washed in
clean water, and lastly, smeared with oil and scraped with a blunt
knife.
In rough brass and brass wares, no less than 16,240 cwts. were
manufactured in the Prussian States in the year 1832.
For musical purposes, the brass wire made in Berlin, has acquired great
and merited celebrity; but that of Birmingham is now preferred even by
foreigners.
BRASS COLOUR, for staining glass, is prepared by exposing for several
days thin plates of brass upon tiles in the _leer_ or annealing arch of
the glass-house, till it be oxidized into a black powder, aggregated in
lumps. This being pulverized and sifted, is to be again well calcined
for several days more, till no particles remain in the metallic state;
when it will form a fine powder of a russet brown colour. A third
calcination must now be given, with a carefully regulated heat; its
quality being tested from time to time by fusion with some glass. If it
makes the glass swell, and intumesce, it is properly prepared; if not,
it must be still farther calcined. Such a powder communicates to glass,
greens of various tints, passing into turquoise.
When thin narrow strips of brass are stratified with sulphur in a
crucible, and calcined at a red heat, they become friable, and may be
reduced to powder. This being sifted and exposed upon tiles in a
reverberatory furnace for ten or twelve days, becomes fit for use, and
is capable of imparting a calcedony, red or yellow tinge to glass by
fusion, according to the mode and proportion of using it.
The glass-makers’ red colour may be prepared by exposing small plates of
brass to a moderate heat in a reverberatory furnace, till they are
thoroughly calcined, when the substance becomes pulverulent, and assumes
a red colour. It is then ready for immediate use.
BRASS COLOUR, as employed by the colourmen to imitate brass, is of two
tints, the red or bronze, and the yellow like gilt brass. Copper filings
mixed with red ochre or bole, constitute the former; a powdered brass
imported from Germany is used for the latter. Both must be worked up
with varnish after being dried with heat, and then spread with a flat
camel-hair brush evenly upon the surface of the object. The best varnish
is composed of 20 ounces of spirits of wine, 2 ounces of shellac, and 2
ounces of sandarach, properly dissolved. See VARNISH. Only so much of
the brass powder and varnish should be mixed at a time as is wanted for
immediate use.
BRASS FOIL. Dutch leaf, called _Knitter_ or _Rauschgold_ in Germany, is
made from a very thin sheet brass, beat out under a hammer worked by
water power, which gives 300 or 400 strokes per minute; from 40 to 80
leaves being laid over each other. By this treatment it acquires its
characteristic solidity and lustre. See above, the process for
converting the copper superficially into brass by the fumes of zinc.
BRAZING. (_Braser_, Fr.; _Messing-lothung_, Germ.) The soldering
together of edges of iron, copper, brass, &c., with an alloy consisting
of brass and zinc, sometimes with a little tin or silver. The surfaces
to be thus united must be filed perfectly bright, and not be soiled with
the fingers or in any other way. The granular or nearly pulverulent
alloy is usually wetted with a paste of ground borax and water, applied
in this state, dried, and then exposed carefully to bright ignition at a
clear forge fire. Some workmen enclose the part to be soldered in a clay
lute, but others prefer leaving it uncovered, that they may see when the
solder has flowed freely, and entered into all the seams.
BRAZIL-WOOD. (_Bois de Fernambouc_, Fr.; _Brasilienholz_, Germ.) This
dye-wood derives its name from the part of America whence it was first
imported. It has also the names Fernambuca, wood of Saint Martha, and of
Sapan, according to the places which produce it. Linnæus distinguishes
the tree which furnishes the Brazil wood by the name of _Cæsalpinia
crista_. It commonly grows in dry places among rocks. Its trunk is very
large, crooked, and full of knots. It is very hard, susceptible of a
fine polish, and sinks in water. It is pale when newly cleft, but
becomes red on exposure to the air.
It has different shades of red and orange. Its goodness is determined
particularly by its density. When chewed, a saccharine taste is
perceived. It may be distinguished from red saunders wood, as the latter
does not yield its colour to water.
Boiling water extracts the whole colouring matter of Brazil-wood. If the
ebullition be long enough continued, it assumes a fine red colour. The
residuum appears black. In this case, an alkali may still extract much
colouring matter. The solution in alcohol or ammonia is still deeper
than the preceding.
The decoction of Brazil-wood, called juice of Brazil, is observed to be
less fit for dyeing when recent, than when old or even fermented. By age
it takes a yellowish-red colour. For making this decoction, Hellot
recommends to use the hardest water; but it should be remarked, that
this water deepens the colour in proportion to the earthy salts which it
contains. After boiling this wood reduced to chips, or, what is
preferable, to powder, for three hours, this first decoction is poured
into a cask. Fresh water is poured on the wood, which is then made to
boil for three hours, and mixed with the former. When Brazil-wood is
employed in a dyeing bath, it is proper to enclose it in a thin linen
bag, as well as all the dye woods in general.
Wool immersed in the juice of Brazil takes but a feeble tint, which is
speedily destroyed. It must receive some preparations.
The wool is to be boiled in a solution of alum, to which a fourth or
even less of tartar is added, for a larger proportion of tartar would
make the colour yellowish. The wool is kept impregnated with it for at
least eight days, in a cool place. After this, it is dyed in the Brazil
juice with a slight boiling. But the first colouring particles that are
deposited, afford a less beautiful colour; hence it is proper to pass a
coarser stuff previously through the bath. In this manner a lively red
is procured, which resists pretty well the action of the air.
Brazil-wood is made use of for dyeing silk what is called false crimson,
to distinguish it from the crimson made by means of cochineal, which is
much more permanent.
The silk should be boiled at the rate of 20 parts of soap per cent., and
then alumed. The aluming need not be so strong as for the fine crimson.
The silk is refreshed at the river, and passed through a bath more or
less charged with Brazil juice, according to the shade to be given. When
water free from earthy salts is employed, the colour is too red to
imitate crimson; this quality is given it by passing the silk through a
slight alkaline solution, or by adding a little alkali to the bath. It
might, indeed, be washed in a hard water till it had taken the desired
shade.
To make deeper false crimsons of a dark red, juice of logwood is put
into the Brazil bath after the silk has been impregnated with it. A
little alkali may be added, according to the shade that is wanted.
To imitate poppy or flame colour, an annotto ground is given to the
silk, deeper even than when it is dyed with carthamus. It is washed,
alumed, and dyed with juice of Brazil, to which a little soap water is
usually added.
The colouring particles of Brazil wood are easily affected, and made
yellow by the action of acids.
They thus become permanent colours. But what distinguishes them from
madder and kermes, and approximates them to cochineal, is their
reappearing in their natural colour, when they are thrown down in a
state of combination with alumina, or with oxide of tin. These two
combinations seem to be the fittest for rendering them durable. It is
requisite, therefore, to inquire what circumstances are best calculated
to promote the formation of these combinations, according to the nature
of the stuff.
The astringent principle, likewise, seems to contribute to the
permanence of the colouring matter of Brazil wood; but it deepens its
hue, and can only be employed for light shades.
The colouring particles of Brazil wood are very sensible to the action
of alkalies which give them a purple hue; and there are several
processes in which the alkalies, either fixed or volatile, are used for
forming violets and purples. But the colours obtained by these methods,
which may be easily varied according to the purpose, are perishable, and
possess but a transient bloom. The alkalies appear not to injure the
colours derived from madder, but they accelerate the destruction of most
other colours.
In England and Holland the dye-woods are reduced to powder by means of
mills erected for the purpose.
The bright fugitive red, called fancy red, is given to cotton by
Nicaragua, or peachwood, a cheap kind of Brazil wood.
The cotton being scoured and bleached, is boiled with sumach. It is then
impregnated with a solution of tin (at 5° Baumé, according to Vitalis).
It should now be washed slightly in a weak bath of the dyeing wood, and
lastly, worked in a somewhat stale infusion of the peach or Brazil wood.
When the temperature of this is lukewarm, the dye is said to take
better. Sometimes two successive immersions in the bath are given. It is
now wrung out, aired, washed in water, and dried.
M. Vitalis says, that his solution of tin is prepared with two ounces of
tin and a pound of aqua regia made with two parts of nitric acid at 24°
Baumé, and three parts of muriatic acid at 22°.
For a rose colour, the cotton is alumed as usual, and washed from the
alum. It then gets the tin mordant, and is again washed. It is now
turned through the dye-bath, an operation which is repeated if
necessary.
For purple a little alum is added to the Brazil bath.