The St. Mary banner. (Franklin, Parish of St. Mary, La.) 1889-1931, 1907-04-27
EEN USES FOR MICA.
Electrical Industry Demands What
Are Called Reconstructed Plates.


The mining of mica has grown to
be an important industry, especially
since it has been found to be an in
sulator OF great value in electrical ap-
paratus; but little is popularity
known of its sources. Some inter-
esting information is given in an ar
ticls on The Uses Of Mica" contrib
uted to Cosmos (Paris) by Mr.. Four
ques Mica has been used for CEN
turtles, he notes, but its uses have
greatly multiplied il recent years.
Once its only value was as glazing
for lanterns or as decoration, but
it is now applied in many new ways,
due especially to the development OF
the electrical industries. The term
mica" embraces a group OF complex
silicates. It's most remarkable char
acteristic, common to all these vari-
cites, is the ease with which they
split into thin, flexible and often
transparent leaves. In thick plates
it appears Opaque with black Or
colcred reflection. This is due to the
innumerable surfaces OF cleavage
from which the light is reflected sue
cessiyely, finally being entirely alb
sorbed. Transparent sheets OF pale
color are often utilized for glazing,
especially in stoves and lamps, and
such use absorbs about a third of the
worlds supply. The writer contin-
ueS:
The most important use, however.
is now as an insuiator in electrical
work Mica is infusible or nearly SO,
impermeab,e to moisture, elastic,
flexible and cleavable; these quail
ties are not possessed all together
by any other known substance. 1t
is thus employed for the insulation
of the wires and bars OF the arma-
lures in dynamos, that is to say, be-
tween the conductors and the iron
core. For this very flexible mica
is requireG-not white mica, but am
Der coiored. Armatures with mica
insulated conductors are incombusti-
Bile.
1t serves also for the manufac-
ture of the resonating diaphragms of
telephones ard monographs.
I'm leaves in natural mica there
are often holes, striae, or small in
Guided quartz crystals, which greatly
limit it's use. The inclusions, in par
ticular, facilitate the establishment
of short circuits. Thus the electrical
industry has recourse to the use OF
| plates of reconstructed mica.
ITO obtain these, sheets of paper
as large as required are spread with
gum lac, and powdered mica is
sprinkled over them in as uniform
| layer as possible. After drying, a
second layer Of gum is applied, then
| more mica, and so on, until the de-
sired thickness is reached. The plate
is subjected to a pressure of about
| 1900 pounds to the square inch and
! at the same time heated by steam.
| The product thus obtained is homo
| geneous, free from cracks, of uniform
thickness, and does not absorb mois-
! ture if the heating has been properly
| done. 1t may be sawed, cut and
| pierced with ease. Finally, it is
| cheaper than natural mica. Conse-
| ouently, it has taken the place of
the latter for work of great size and
even for that of ordinary size.
I'm small establishments the man
ufacture of this 'micanite' is carried
on by hand; but on the large scale
it is performed mechanically, SO that
one woman may make about seven
cubic feet in a day. which would re-
| quire the work of twenty women
using their hands only. The manu-
| facture of tubes, rings, ETC.. is car
F! ried on in similar way.
! mica powder is used for the dec
grafton Of wallpaper. as in the pro-
duction of snow effects; it is also
largely employed in compositions that
| are non-conducting to heat.
f. "Veins of mica are found in all
countries, but the industrial market
is supplied chiefly by India, Canada
and the United States. "-Transla,
ton made for The Literary Digest.