Clarke courier. [volume] (Berryville, Va.) 1869-1997, 1899-09-13
THE LOOKING GLASS.
MERCURY BACKS AND PATENT BACKS
ARE VASTLY DIFFERENT.

How the TWO Methods Are Used In
the Mnnufncturc o. Nirrc-s-Wby
Some Glasses Always Have n Fad
ed, SpecLIcd Appearance.
II is popular fallacy that all mir
rors have mercury. or quicksilver,
backs As matter or fact. not over
per 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
years ago. but they do not know that
these are not the old time reliable mer-
curry back mirrors.
The mirror now manufactured is
known 10 the trade rs the patent
back mirror" not that there il any pat
cnt on the process used. but simply
TO distinguish il from the mercury
bac. mirror. \ number OF years ago
the mirror manufacturers began To
substitute the patent back for the mcr-
curry type of mirrors. without notify
ing ,he consumer cor furniture iobbcrs
OF the change: So quietly was the eVO-
luton accomplished that il took some
time for the furniture dealers 90 realize
tho change. and today many careful
houSci1ccpcr wears herself OUT phys
ically trying To- polish thc speckled or
faded surface or patent back mir
ror." when tho cause Df tl" trouble is
impcrfections ou the back ami not on
the face. or surface of tine glass
The rejecting surface or ~patcnt
back mirror" is composed OF "a chemical
solution OF nitrate OF silver. precipi-
tatcd ON the surface of the glass which
* subject To- change from exposure 10
light. changes OF temperature or moist
ure. while the rejecting surface OF a
mercury mirror is composed OF two
metals. mercury and tin which form
an amai-am imucrvious Go AMI not ar
fected 10y changes of temperature or
moisture and retains it's initial rencc-
tive brilliance unimpaircd for ages.
The process OF manufacturing a mer-
curry back mirror is first 20 clean and
thoroughly dry the plate OF glass. then
spread a sheet OF tin foil a little larger
than the glass on a silvcriu- table. the
top or which may hc stone or heavy
plate glass In either case IL must
have a perfectly level and smooth sur
face. Brush the foil out perfectly
smooth and pour on liquid mercury 10
the depth of a quarter OF an inch This
mercury is retained ON 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
50 the glass cannot be floated on the
mercury. but must be pushed into il So
that 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 successfullv
hoated. heavy iron weights are placed
thereon 10 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 bv
means OF vertical screw under one
of its edges and the surplus mercury
drained off into 4 suitable vessel The
mirror is kept in this position for ~
hours 10 enable the amalgam 70 solidi-
fy sufficiently So that il 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
n rack 10 dry ana allowed To remain
from 20 10 80 days until sufficiently
dry.
The progress of manufacturing n
patent back mirror" is rs follows.
First wash the glass clean. then place
ii on I table heated 10 temperature
of l2O degrees. y solution is prepared
composed of the following proportions
of chemicals: -Four ounces of nitrate of
silver. IL ounces OF distilled water. =
ounces OF tartaric acid and ounces Of
stronger water Of ammonia. This
forms 4 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 or The silvered
surface is washed with distilled water
and placed on rack I'm Il drying room.
the temperature OF which is about 80
degrees. and left there for half an
hour, after which il receives a coating
of Shellac varniSh. to which is added
n little later a heavy coat Of paint.
This is allowed 10 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 manufactured 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 Ii can also
be handled with less danger Of damage
In packing and shipping. which Is
greatly I'm Its favor from the mirror
trade point of vicw.-St. ouis Globe
Democrat.
Hereditary strength of the On
The strength Of an OK i'm pulling a
load is remarkable. How did IL learn
to pun SO marvclouSly? Without doubt
this quality is traccablc to the habit
found among al wild cattle OF waging
war with their horns At Chillinyham