The Abbeville press and banner. [volume] (Abbeville, S.C.) 1869-1924, 1907-03-06
NEW USES FOR MICA.
Electrical Industry Demands What
Are Called Reconstructed Plates.

are tulcQ RECONSTRUCTED ffdCeS.
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 it's sources. Some inter-
esting information is given in an ar
ticle on THE Uses of Mica" contrib
uted to Cosmos (Paris) by Mr.. Four
Dues. Mica has been used for GEN.
turtles, he notes, but it's use have
greatly multiplied in recent years.
Once it's only value was as a glazing
Tor lanterns or as a decoration, but
1t is now applied in many new ways,
due especially to the development Of
the electrical industries. The term
mica" embraces a group of complex
s~ilicates. Its 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 a black or
colored reflection. This is due to the
snnumerable surfaces of cleavage
from which the light is reflected sue
:essively, finally being entirely abb
;orbed. Transparent sheets of pale
olor 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:
1.-The most important use, however,
Is now as an insulator in electrical
work. Mica is infusible or nearly so,
impermeable to moisture, elastic,
dexible and cleavable; these quail
lies 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 a very flexible mica
IS required-not white mica, but am
Der colored. Armatures with mica
insulated conductors are incombusti-
BILE.
1T serves also for the manufac-
ture Of the resonating d~iaphragms OF
telephones and 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 a
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-
quently, it has taken the place of
the latter for work Of great size and
even for that of ordinary size.
"In 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
ried on in a 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.
Veins of mica are found in all
countries, but the industrial market
is supplied chiefly by India, Canada
and the United States. '-Transla-
tiop made for The Literary Digest,