The Topeka state journal. [volume] (Topeka, Kansas) 1892-1980, 1919-02-15
TOPEKA STATE JOURNAL
INFORM ATION
BUREAU
FREDERIC J. HASKIN. Director.
Washington. D. C
OPTICAL GLASS IN AMERICA.
Washington. D. C

OPTICAL SrlAASS In a4AEINAO1A.
Washington, D. c., Feb. 11.-From
two to four thousand pounds of OPP
teal glass every month are now being
turned out by government glass fac
tory operated under the management
of the bureau of standards. In addi-
ton to this, there is one large, private
firm which has been doing govern
ment work thruout the war, and is
still producing 100 to $50 tons of OPP
teal glass month.
This output of optical glass repre-
sents the newest American industry,
and one which grew most completely
out of war conditions. Practically no
high grade optical glass was made in
America before the war Most OF II
was imported from Germany. Amer
lean manufa cturers had to learn the
business by experiment, devise equip
ment and build factories. the story
of how they did this. what difficulties
they encountered, and how much the
new industry amounts to, may now be
told in full.
With the entry of this country into
the world war there developed a great
need for optical glass for range find
ers telescopes, field glasses, peri
scopes, Photographic lenses and other
optical instruments of warfare. This
need was absolutely vital The war
could not be won by any nation tnat
teal glass. This had been proved in
the beginning of the war when the
French lost thousands of men because
the Germans were so much better
equipped in this respect, ard could
therefore sight the enemy long BEFORE
the enemy discovered them.
The seriousness of the situation was
fully realized. The result was that q
number of government and private
| experts combined forces and plant
I 10
optical glass factory in the United
States.
The making of optical glass is
highly specialized art. and the me.
chanical difficulties in the way of
reaching a production basis some
times appeared to besinsurmountabl
| One of the first difficulties encoun-
tered was to get clay for making the
vessels in which the glass is melted.
The clay first used had certain metal
| lie deposits which were absorbed into
the glass and gave it greenish or
! blush tint instead of leaving it clear.
| The most common of these elements
was iron which gave the glass green
! ish tint BY persistent experimental
| ton this was finally overcome.
| Then there was a great deal of trou-
| BILE with bubbles in the glass. This was
| due to improper annealing. The proc
ess of making glass is very similar to
| that of making molasses candy. The
| chief ingredients are sand. as a basis.
| potassium carbonate, and some metal
| lie elements are used to produce the
| optical qualities of the glass, and only
one is used to produce a given kind of
| glass.
The ingredients are placed in the
/ clay bowls and fused into a viscouS
mass This is cooked from forty
| eight to sixty hours, and rs stirred con-
| stantly. The heat must be shut off
at a certain time, or else one or more
of the optical qualities will be af-
fected.
! The motion glass has of course
bubbles in it, and while the larger
| ones rise to the surface and evap-
crate, the smaller ones under the sur
face rise more slowly and are often
| left in the-glass when it is cold. This
was particularly true in the first
months of the development of this
new American industry. Improved
methods of fusing and cooling, how
| ever, have eliminated this to a great
| extent, and the few bubbles that now
! remain are either on the outer shell
| SO that they can easily be broken off
and thrown away, or are so small tt at
they will not affect the optical quail
tiles of the glass.
The variety of optical glass now ob-
| tainable is not so great as that listed
by a large German firm Immediately
before the warn This firm offered
optical glass of different physical quail
tiles to the number of about IT'S. 1t
is doubtful if more than twenty-five
4 varieties can be obtained in this coun-
try today. But the physician who
wants microscope, or the motion pic
ture operator who wants a lens, either
for photographing. or projecting, Oh
the ordinary citizen who wants a field
glass, or nagnifier for his library ia BILE
or any other optical instrument OF
common use, can purchase one con-
tanning glass of American manufac-
ture with the assurance that the best
efforts of real exp .rts have gone nto
its production. Their work has beer
: proven by the perfor nance of similar
instruments in the hands of our ffght-
| ing forces.
The only varieties that are not
manufactured here are those used by
: scientists engaged in the most difficult
. microscopic investigations.
Up to- the present time the bulk OF
the optical glass produced by, Ameri-
can manufacturers has been taker
2 over by the government for the army
and navy. Now that the requirm ent.
of these have been reduced, and manS
| government contracts have been can.
! celled, the manufacturer is AGAR
t placing optical instruments before the
public.
l However, there has always been a
very strong prejudice existing among
!, scientists in favor of German-made
: optical instruments, and American
manufacturers have avoided puttins
on the market a similar product
knowing that it could not be success
. fulS pushed in the face of the pre-
JUDGE against it.
= viii this still be the case? Afte,
2 conditions again become normal will
D Americans prefer to buy the German.
, made product. or will they show theil
appreciation of the efforts of the
optical industry ira this country By
l purchasing the home product? Il
q they feel any doubt as to the quality
of the instrument offered, they should
submit it to the United States bureau
t or standards. whose staff of expert.