Amador ledger., 1901-12-06
COUNTERFEIT GOLD.
GLIDING POWDERS ARE MADE OF
COPPER AND SPELTER.

How the Material That Gives the
Shining, Metallic Finish to Mirror
and Picture Frames Is Produced.
Gold Leaf without Gold.
How many persons who see the shin
Ing gold In colored printing and on
mirror and picture frames know that
gold does not enter at all into the COM
position of the stuff that produces these
golden effects?
The shining metallic effect is pro-
duced by fine powder made from a
mixture of bronze and spelter. This
offers the cheapest and best means of
giving the rich surface demanded in
wall papers, printing, TYPOGRAPHY, fres-
Going and in vast range of manufac-
tured articles of wood, paper and iron.
The material used is so called Dutch
metal, an alloy of copper and spelter.
The relative proportions are varied to
produce different colors. The larger
the percentage of spelter the lighter or
more yellowish will be the tint of the
alloy.
The copper and spelter are smelted in
graphite crucibles containing about 400
pounds Of metal, which, when COM
pletely fused, is run off into molds,
forming half round ingots two feet
long by half an inch in thickness. Aft
er cooling these are bound into bundles
and sent to the rolling mill, where they
are passed cold nine times through a
double set of steel rolls under enor-
nous pressure. This flattens them and
draws them out into thin ribbons from
SO to 60 feet long and something more
than one inch wide Cold rolling IN
der such extreme pressure makes the
metal brittle, so it passes to the an
healing furnace, which is heated by
wood fire, as the sulphur In coal or
coke would be injurious to the ribbons.
Having been softened and rendered
ductile by annealing. they are cleansed
IN an acid bath, cut into lengths of
about three feet and collected In bun
dies of 40 or 90 strips each. They are
laid between sheets of zinc and passed
under hammers which beat the metal
strips to the thinness of tissue paper
This requires six successive beatings,
produce uniform and unbroken foil.
After the third beating the metal strips
are taken from between the sheets Of
zinc, loosened from each other and
cleansed by immersion in a bath of
tartrate of potassium. The cleaning is
repeated after the last beating. and the
sheets are hung on lines to dry. In the
beginning the rolled strips are a dull
gray metallic color. at the fourth beat
ing the yellowish color begins to show,
and after the sixth they are clear and
bright as gold.
The defective leaves are then thrown
out and the perfect ones cut into small
squares, which are laid together by
hand in packets of several hundred
each and inclosed within an envelope
of sheet brass. The packets return to
the annealing furnace, where they are
softened by heating and slow cooling,
and then go to the beaters, where they
are reduced under f1attening hammers
to the thinness of real gold leaf, so thin
that 1t can be blown away by the
breath.
The manufacture of bronze powder
consists in grading, clipping and pull
verifying the various bronze foils to an
even, impalpable powder and is an In
dustry of comparatively recent date.
1t began as a means of using up and
utilizing the imperfect leaves which
came as waste from the beaters of
gold, silver and bronze. These were
cut by hand into fine clippings and
then ground to powder in hand mills Of
simple construction. With the lapse of
time and the spread of artistic indus
tries the uses of bronze powder In
creased until the demand far outran
the supply of waste, and the leaf metal
is now made on large scale.
The beating process dattens out a
pound Of copper and spelter alloy to an
area Of about 500 square feet, and in
this condition the square sheets as they
come from the brass envelopes are
sheared into small fragments and rub
bed with olive oil through a steel sieve
having ten meshes to the inch and then
passed to the stamping and grinding
machines, where they are pulverized by
steam or water power to the bronze
powder of commerce. The grinding
occupies from one to four hours, &C
cording to the grade or quality Of the
powder to be produced, which is Of
four grades, from coarse to superfine.
The superfuous oil is removed by heat
ing under pressure, and the powder
is then carried into centrifugal clari-
fiers, or grading machines, which, turn
ing at high speed, expel the powder
through fine orifces in the form OF
dust, which settles on inclosed shelves,
according to weight and fineness, the
finer particles at the top, the coarser
below, and in this way the powder Is
divided into its various grades.-New
York PrOsa- :.
Origin of the Clearing House.
In 1775 the bankers Of London rented