The Anderson intelligencer. [volume] (Anderson Court House, S.C.) 1860-1914, 1899-07-26
THE LOOKING GLASS.
MERCURY BACKS AND PATENT BACKS
ARE VASTLY DIFFERENT.

Some Glmxxcs Always Have Fad
ed, Speckled Appearance.
1t is a popular fallacy that all mir
rorS Layc mercury. or quicksilver.
/ backs. As L matter Of fact. not over
Der cent Of the mirrors now sold be-
long to that class. The general public
know that they can purchase mirrors
much cheaper now than they could ten
wears ago but they tlo not know that
these are not the old time reliable .mer-.
curry back mirrors.
The mirror now manufactured is
known to the trade as the patent
back Mirror" not that there is any pat
ent on the process used, but simply
to distinguish it from the mercury
back mirror. 4 number Of years ago
the mirror manufacturers began to
substitute the patent back for the mer-
curry type Of mirrors, without notify
ing the consumer or furniture j0bbcrS
Of the change; so quietly was the eyO-
luton accomplished that it took some
time for the furniture dealers to rc,lliZe
the change. and today many careful
housekeeper wears herself out phys
ically trying to polish the specklcd or
faded surface Of Il patent t'ck mir
ror,' when the cause Of the trouble is
imperfections on the back and not on
the face, or surface Of the glass.
The refecting surface of a patent
back mirror" is composed Of a chemical
solution of nitrate of silver. precipi-
tated on the surface Of the glass, which
is subject to change from exposure to
light, changes Of temperature or moist
ure, while the rejecting surface of Il
mercury mirror is composed of two
metals, mercury and tin, which form
an amalgam impcryiOus to and not af-
fectcd by. changes Of temperature or
moisture and retains its initial rcflec
tive brilliance unimpaired for ages.
The process of manufacturing mcr
curry back mirror is first to clean and
thoroughly dry the plate Of glass. then
spread sheet Of tin foil little larger
than the glass on 4 silvering table, the
ton Of which may be stone or heavy
plate glass In either case it must
have 4 perfectly level and smooth SUI
face. Brush the foil out perfectly
smooth and pour on liquid mercury to
the depth Of quarter Of an inch. This
mercury is retained OH the foil by
small strips Of glass on three sides.
Then float the plate Of glass into the
mercury from the open side. In doing
Sc the glass cannot he foatetl on the
mercury, but must be pushed into it SO
that from beginning to end its lower
edge will cut into the mercury
This operation must be donc with the
greatest care and precision. After the
plate Of glass has been successfully
floated, heavy iron weights arc placed
thereon to give the required degree OF
pressure to force out the surplus mer-
curry which does not unite with the
tin foil The table is slightly tilted by
means of q vertical screw under one
Of it's edges and the surplus mercury
drained off into a suitable vessel. The
mirror is kept in this position for ~
hours to enable the amalgam TO sOlidi-
fy sufficiently so that it can be turned
over without danger Of free mercury
running over the surface Of the ANAL
gam, which would spoil the mirror. AT
the end Of this time the mirror is re-
moved from the table. When removed
from the table, the mirror is placed OH
rack to dry and allowed to remain
from 20 to 80 days until sufficiently
dry.
The progress Of manufacturing a
patent back mirror" is as follows:
First wash the glass clean. then place
it on table heated to tempera turc
Of 100 degrees. A solution is prepared
composed Of the following proportions
Of chemicals: Four ounces Of nitrate Of
silver, 10 ounces Of distilled water, .
ounces Of tartaric acid and ounces Of
stronger water Of ammonia. This
formssa clear. transparent fluid, which
Is poured on the surface Of the glass
and left there for about one hour. The
glass is then tilted and the surplus
solution Is drained off. The silvered
surface is washed with distilled water
and placed on rack in n drying room.
the temperature Of which is about 30
degrees. and left there for half an
hour, after which it receives a coating
Of shellac varnish, to which is added
n little later heavy coat Of paint.
This is allowed to dry. The mirror is
then ready for use.
Such in brief is the method and
process OF producing the patent back
mirror" The great advantage to the
mirror manufactures in the production
Of the patent back" as compared
with the mercury back mirror, is
quite apparent 1t is readily seen that
the "patent back mirror can be pro-
duced in onc-tenth Of the time, for one
fourth Of the labor and about the same
expense for raw material rs compared
with the mercury mirror. 1t can also
be handled with less danger of damage
in packing and shipping. which is
greatly in it's favor from the mirror
trade point of vicw-St. Louis Globe
Democrat
Hereditary Strength of the OA.
The strength Of an OK in pulling Il
load is remarkable How did it learn
to pull so marvclously? Without doubt
this quality is trucelblc to the habit