BRUISING CORN. 
(sheet-tin), is found to make a harder and more 
tenacious bronze, for small objects, but appears 
to be of little benefit to objects of larger size. 
Larger quantities of zinc may be added to bronze 
with the same results, as is often done in statue- 
bronze, bells, &c. A small quantity of lead may 
be added, but it rather diminishes the valuable 
| properties of bronze, rendering it more suscep- 
———EE 
| trate, or acetate of copper. 
tible to oxidation, and tending to separate towards 
the bottom of a large casting. 
Bronzing.— When bronze is exposed for a great 
length of time to atmospheric agents it assumes 
a peculiar greenish or olive hue, arising from the 
formation of a basic hydrated and carbonated 
oxide of copper, or a dark olive hue from sulphu- 
ret of copper. Being an attractive colour, nu- 
merous experiments have been instituted to dis- 
cover a method of obtaining the same result ina 
short time. It is usually effected by means of a 
salt of copper, mixed with other salts, dissolved 
in water or weak acids, and applied to the surface 
with a brush, or the objects are immersed in the 
solution. ‘Two pts. verdigris and 1 pt. sal-ammo- 
niac are dissolved in vinegar, boiled, filtered, and 
much diluted, and the medals, &c., immersed in 
the solution until they acquire the desired colour, 
| when they are washed. Binoxalate and bitar- 
trate of potassa are employed with sulphate, ni- 
After attaining the 
bronze-colour, the objects should be thoroughly 
washed in pure water, with repeated washings, 
| to remove every trace of salts or acids, and 
thereby prevent the surface from farther change. 
Different tints may be imparted to bronze, from 
a reddish to a light yellow, by acting upon it 
with acids and salts, by which either copper or 
zinc may be extracted. Thus, boiling muriatic 
acid extracts a considerable quantity of tin be- 
fore attacking the copper. Mixtures of salt- 
petre, common salt, and sulphuric acid, may be 
made to extract either copper or the white 
metals, and thus the colour may be varied. 
Tinning copper—This depends upon the af- 
finity of copper and tin, whereby a small quan- 
tity of the latter is fixed upon the surface of the 
former. The important principle in tinning is 
that the surface of the copper be clean and per- 
fectly free from oxide, and be so maintained during 
the process. This is attained either by the use 
of sal-ammoniac or resin, with melted tin, or by 
cream of tartar in solution and grained tin. The 
sal-ammoniac is either dissolved and brushed 
over the surface of the copper, or it is heated and 
its vapour condensed on the surface; tin is then 
introduced, melted, and rubbed over the surface 
with tow. The process with resin is conducted 
in a similar manner. Tinning with sal-ammo- 
niac is more durable, but requires the use of 
nearly pure tin; tinning with resin allows the 
employment of an alloy of lead and tin. The 
quantity of lead should never exceed § or 1o of 
the tin, as it might otherwise prove detrimental 
to those employing food prepared in such vessels. 
a 
BRUNSFELSIA. 009 
Tinned vessels, whether containing lead or not, 
are not to be recommended in place of good bell- 
metal, certainly not for the preparation of food, 
especially if the latter be acid, or the vessel is to 
be heated. 
Whitening pins.—Copper or brass is easily tin- 
ned in the wet way. Thus, in the pin manufac- 
ture, when they are completely formed, they are 
cleansed in a pickle of sulphuric acid, vinegar, 
cream of tartar, &c. They are then thrown into 
a copper vessel, stratified with grained tin, cov- 
ered with water, cream of tartar added, and the 
whole boiled. The cream of tartar probably acts 
by dissolving a portion of tin, and then transfer- 
ring it to the pins, which, containing zinc, be- 
come electric by contact with tin. 
Inutation of Bronze—The pigments and var- 
nishes are applied to the surface of wood, plaster, 
&c. The objects to be bronzed are first covered 
over smoothly with a coat of size or.oil-varnish, 
and when nearly dry, the metallic powder made 
from Dutch foil, gold leaf, mosaic gold, or preci- 
pitated copper, is applied with a dusting-bag, and 
then rubbed over the surface with a linen pad; 
or the metallic powders may be mixed with the 
drying oil beforehand, and then applied with a 
brush. Sometimes fine copper, or brass-filings, 
or mosaic gold, are mixed previously with some 
pulverized bone-ash, and then applied in either 
way. A mixture of these powders with mucilage 
of gum arabic is used to give paper or wood a 
bronze appearance. The surface must be after- 
wards burnished. Copper powder precipitated 
by clean plates of iron, from a solution of sul- 
phate or nitrate of copper, after being well washed 
and dried, has been employed in this way, either 
alone or mixed with pulverized bone-ash. A 
finish is given to works of this nature by a coat 
of spirit-varnish. The iron-coloured bronzing is 
given by black lead or plumbago, finely pulver- 
ized and washed. 
BRUNIA. A genus of small, evergreen, orna- 
mental, greenhouse shrubs, forming the type of 
the order Bruniacec. This order comprises seven | 
genera ; and has, in the gardens of Great Britain, | 
about seventy species. All are small heath-like 
shrubs, highly ornamental in both flowers and 
foliage ; and, with the exception of one from Ma- | 
dagascar, all are natives of the Cape of Good 
Hope. They differ from the currant tribe by 
having dry fruit; from the Escallonia, by hav- 
ing few seeds; from the Rhamnacez, by having 
a minute embryo; and from the Umbelliferee and 
the Araliaceze, by their not having their flowers 
in umbels, Their nearest affinity is to the cur- 
rant tribe. About twenty-five species of the 
genus Brunia have been brought to Britain from 
the Cape of Good Hope; and most of these have 
a height of about two or three feet, while all pro- 
duce white flowers in summer. Several other 
and quite recently introduced species have been 
assigned to four other genera. 
BRUNSFELSIA. A genus of tender, ever- 
