Idaho semi-weekly world. [volume] (Idaho City, Idaho Territory) 1875-1908, 1891-09-08
CAMEO CUTTING.
DESCRIPTION or 4 PROCESS GEM
ERALLy LITTLE UNDERSTOOD.

l.
Canoes are OF two kinds--those cut in
stone, or in pietra dura, and those cut on
mollusk shells. The latter are fourd chiefly
on the African aHd BRAZILIAN coast They
show. as a rule, two layers pale coffee
color, or deep red and white. They are elias
sified in the trade as the Bulls Mouth, the
Black Helmet, and the Queens Conch The
first has red or sardonyx inner coat, the
second a blackish ground and the third
pink ground. The first are found mostly
at Madagascar and Ceylon, and the second T
at Jamaica, Nassau and New Providence
They are formed of three distinct layers VI I
calcareous matter, and their peculiar struct-
ure, while it affords the greatest protection
to the animal, serves also to give the cutter i
a secure foundation for his work
Designs upon shell canoes, which are very l
much softer than stone canoes, may be |
effected by the process necessary in the treat, !
ment Of the latter. Or, when the shell |
yields readily, the cutter does not resort TO
the engine, but, having drawn an outlins
upon the prepared ground. cuts away from
it as the wood engraver does, with tools care
fully made for this particular industry. They
are files and gravers. The tool most used is
fat On side and round on the other, and
serves therefore either as a gouge or chisel
OF Sicilian origin, the manufacture OF shell
canoes was carried from Italy to Paris; and
more than one-half the output of the lapi-
diaries goes to England and is thence sent to
the United States. The shell cameo is, Of
course, inferior, both in durability and ar
tistic quality, to the stone canoes, which
enable the engraver to give considerable
relief and remarkable fidelity to any design
which may be placed upon them.
The prize stones are those which show four
or five distinct layers OF different colors
Thus, for heroic head, the face would be in
the highest color, the helmet dark, the crest
a shade lighter, and the ground gray. Art
| lists like to cut a Medusa on stones having
| red layer, 80 as to use that shade On the
snakes. The stones now in favor are those
showing layers of black and white Of equal
breadth. Before process Of colorilg was
founder rebound, rather, for it is now
! known to have been in Use and lost in an
| tiquity German agates of two shades of gray
were much in demand, and many beautiful
designs were engraved upon them. Very few
canoes seen in jewelers. cases confess to the
careless observer that their beautiful co.cTs
| and high polish are due more to chemistry
than to nature. The eoloring process is very
| curious
The round chalcedonous pebble is the orig
1 IL
| river beds At Oberstein it is found under
the rocks that are the great ribs Of the high
formation, and it lies freely also in the
ground like flint stones in chalk From the
mills of Oberstein and Idar the lspidaries of
the world are supplied When the pebble is
first tested the trier breaks off small bit
and moistens the fragment with his tongue
He watches keenly the rapidity with which
the moisture is absorbed and whether the
ABSORPTION is in bands. and in one band moro
rapidly than in another. Thus he ject-
ures its capacity to receive color. The peb-
bic may be nothing but what we cal agate;
but chemistry is going to make it onyx or
sarGlonyx. By its sensitiveness to moisture
he rates its commercial value, and then il
goes not to the engraver but to the Sitting
mill, where its roughness is ground off, and
it is cut so as to bring the white stratum OF
layer uppermost. Then it is ground with
emery and polished with water and rotten
stone on pewter lap.
1t goes next to the colorer. He immerses
it in honey and water, and for several weeks
it is kept in its bath at temperature JUS
below boiling. When done it is transferred
to another tub, and covered with sulphuriC
acid heated to $50 or 100 dogs. After ter
hours it is finished It goes next into clear
ing it lies in oil, which removes the appear
ance of flaws and adds to the brilliancy o.
the polish. Bran removes the oil The Sc
crets of the coloring have never been fully
understood, and the operation of the variou
! influences is uncertain 1t is taken 70
granted that the honey inyades the pores anl
/ is carbonized by the sulphuric acid The de
position of the carbon increases the color Q
each band which the honey has permeated
: If the color Of the stone is uniform through
out it is natural; if it has been chemical,
: heightened or produced by sulphuric acid
: which makes the black ground, or nitri
f acid. which produces the carnelian ground
: the color Will be found on examination
+ superficial and uneven. Only experts cal
t detect pure chalcedony from colored agates.
4 If "a portrait is to be engraved upon tn
/ stone, many artists prefer first to make th
model in wax and prove it in plaster, as tn
engraver of old tested the design he intende
to put in enamel upon gold The model
n ing accepted and the stone selected Of th
S size and strata desired, it is placed upon
q cork and leather handle which holds it S
V firmly that it will not be displaced in ii
5 slightest degree by the action of the engin'
d Then the artists task actually begins II
Il slightest error of eye, the least iniirmity {
d hand, and the failure is complete. The el
/, graver and etcher apply sharp instrumeI
k to the ground, upon which they operat
a The cameo engraver applies the ground to
k sharp instrument, which does the cuttS
r and which, in Amsterdam, in the damon
e factories, is run by steam -oTer.
s The engine is a miniature lathe head
t, stands ON a solid tabfa before the engrave
n and it is confronted by rows of small irC
l. tools, some of which look like little whes
n on the ends Of IRON stems; and most of the
l. like dentists tools of half the comma
y length A microscope would be neceSsai
N to discover that the smallest Of them ends
= a disc: for some Of the discs are less than L
t. one hundredth part of an inch in diamete
It These little wheels are the cutters on q
10 cameo ground. They receive touch of {
s, and diamond dust just before the oleratit
Id commences; and the diamond dust cuts viii
the oil polishes The artist must chan
them frequently, according to the depth
10 the incision. the nature of the grain, and
direction of the line. His training mu
therefore, be slow and accurate, his eye TIT
and his sense of form developed into micrt
copic exactness. Many sc1iptors prefer t
training for cameo portraiture as an inval
. able part of their education st. Gaude
le was cameo cutter.-Chicago Tribune.
Id A Queer Whim.
lie An English nobleman good mar
y many years ago took it into his hes
"a ii ,,-asal-e ON, MlJInr En-