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

O., the Mnuufncturr of Nirrora.W-h,
some Giusncn Always Have O Fad
ed. sperLied appearance.
1t Is a popular fallacy that all mir
rOrs hayc mercury or quicksilver.
backs. AS a matter Of fact. not over
per cent Of tile mirrors now sold be-.
long to that class. The general public
know that they can purchase mirrors
much cheaper now than they could ten
years ago. but they do not know that
these are not the old time reliable nier-
curry back mirrors.
The mirror now manufactured ia
known to the trade as the patent
back mirror" not that there Is any pat
ent OIL 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 jObbcrs
Of the change; so quietly was the evo-
luton accomplished that 1t took some
time for the furniture dealers to rcnlize
the change. and today Inuny careful
housekeeper wears herself out phys
ically trying TO polish the spcckled or
faded surface of patent back mir
rOr," when the cause Of the trouble Is
imperfcctions OH the back and not on
the face, or surface Of the glass.
The refiecting surface OF patent
back mirror is composed OF Il chemical
solution of nitrate OF silver. preclpi-
tated OIL the surface OF the glass, which
Is subject to change from exposure To
light, changes OF temperature or moist
ure. while the reticcting surface of Il
mercury mirror is composed Of two
metals, mercury and tin. which form
an amulgam impcrvious to and not af-
fected by changes OF temperature or
moisture and retains It's initial retlcc-
tive Drilliance unimpaircd for ages
The process Of manufacturing ii mcr-
curry bacll mirror liz first to clean ana
thoroughly dry the plate OF glnss. then
spread a sheet Of tin foil n little larger
than the glass on Il Silverlng table. the
top OF which may he stone or heavy
plate glass. In either case II must
have perfectly level AMI smooth sur
face. Brush the foil out perfectly
smooth and pour OH liquid mercury to
the depth Of a quarter Of an inch This
mercury Is retained Oh the foil by
small strips Of glass OH three sides.
Then float the plate OF glass into the
mercury from the open side. In doing
80 the glass cannot he flou ted on the
mercury, but must be pushed into II SO
TINT from beginning to end its lower
edge will cut into the mercury.
This operation must be done with the
greatest care and precision. After the
plate OF glass has been successfully
fiOated, heavy iron weights are 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 vertical screw under one
Of It's edges and the surplus mercury
drained of into a suitable vessel. The
mirror Is kept In this position for -
hours to enable the amalgam to solidi-
fy sufficiently 80 that 1t 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 * re-
moved from the table. When removed
from the table, the mirror is pIaceti OH
a rack to dry and allowed to remain
from 20 to 80 days until sufficiently
dry.
The progress OF manufacturing a
patent back mirror" IL as follows:
First wash the glass clean. then place
1t on q table heated to a temperature
or gO 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 fartaric acid and ounces OF
stronger water Of ammonia. rhis
f0rEtlA;a u clear. transparent fluid. which
ist pUnfed on the surface OF the glass
atiasleft there for about one hour. The
glass -is then tilted and the surplus
solution is drained of. 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 nm
hour, after which 1t receives q cOating
OF shellac varnish, to which Is added
a little later heavy coat OF paint.
This is allowed to dry. The mirror is
then ready for usc
Snch In brief is tic method and
process Of producing the patent back
mirror" The great advantage to the
mirror manufacturer 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 One-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 its favor from the mirror
trade point OF view.-St. Louis Globe
Democrat
Hereditary Strength of the OK.
The strength OF an OK in pulling IL
load Is remarkable. How did it learn
TO pull 80 marvelously? Without doubt
this quality is traceable to the habit