The new North-west. [volume] (Deer Lodge, Mont.) 1869-1897, 1885-10-30
DEER LODGE, MONTANA, OCTOBER 80, 1885.
TEMPERED GLASS.
RESULTS ATTAINED BY A DRESDEN
MANUFACTURER.
The Toughening Process OF De In Bastie
and Its Failure--Mr. Frederick Sle-
mems Methods - Hardened
Glass by Simple Processes
Philadelphia Record

Philadelphia Record.l
When piece of ordinary glassware Is
blown or ca It in q mold the subsequent cool
ing proce IS docs not equally affect all its
parts and surfaces, and its molecules are
consequently thrown into . state OF tension
or strain The brittle quality resulting from
this condition has become q popular syn
onym for weakness and uureliability, and 1t
has long been the most formidable obstacle
to q proper development Of the glass manu-
featuring industry For u,auy ysars siesO-
makers have sought for sopne process BY
which glass might be made as stout as cast
iron and as hard as its original quartz,
while retaining the pliability in manufact-
ure that has made 1t q thing OF universal
use and necessity. Such discovery would
be followed by many important changes In
manufactures, in architecture, and In many
Of the appliances and implements OF daily
life A material as strong IS iron ana OF
but one fourth its weight, and susceptible OF
an almost infinite variety OF decoration,
would unquestionably be q new and i'm
portant resource in the hands OF civiliza-
ton.
In their search for this new material the
glassmaksrs have not been entirely unsuc-
cessful, although the result Of their labors
up to this time is shown only by q few frag-
mentary wares, which have hardly attracted
public notice. The way to success Is difficult
and new chemical compounds, independent
of present manufacturing processes, may be
required before the desired ead Is attained.
The toughening process Of De In Bastie,
which promised so much ten years ago, has
dropped into abeyance, and nothing useful
Is anticipated from it in the future. II con-
sisted simply In heating the glass and
plungng it Immediately into hot oil The
articles thus toughened were always liable
to break spontaneously into fragments; but,
generally speaking, unless broken very soon
they would last long time.
But this process presents many difficult
ties. 1t is not adapted t, all forms OF glass
manufacture, and the percentage Of loss by
breakage Is very large The cause OF the
breakage Is inherent in the operation itself,
which cools the articles in proportion to
their surface, instead of In proportion to
their bulk, and thus induces q molecular
strain likely at any time to cause complete
rupture This commercial objection, to-
gether with the difficult and uncertain
character of the process, has prevented De
Ia Bastie's method from producing q sensi.
BILE impression upon the glass manufactur-
ing process Of the world Like many other
clever novelties, 1t has been interesting from
scientific standpoint, but failure COM
mercially.
But il De Ia Bastie has failed in attaining
his object. he has at least pointed the way
through which others may reach the prize.
Six years ago Frederick Siemens, then al
ready Of established reputation as prac-
tical scientist and man Of affairs, began at
his Dreslen glass-works the production by
original processes Of toughened, or, as he
prefers to call it, hardened glass The value
Of bis output for the first year was $4,000,
and there has been q steady annual increase
until last year it amounted TO over SIS, ,0O0
Mr. Siemens describes his method at
length in a paper which he recently read
include three distinct processss-press-
hardening, casting. and hard -tempering-
and all these are based upon the
principle of absolutely uniform heating
and cooling This means simply that
at any given instant in the processes OF
heating and cooling every portion Of the ar
ticle shall be OF exactly the same tempera-
ture. The devices to secure this end are
varied according to the var GUS shapes to be
treated In practice it has been found
some what difficult to attain the required
theoretical perfection; but this is not q mat.
ter Of so much Importance, since technical
skill will follow upon experience.
Mr. Siemens seems to have hit upon the
right path, which, in the matter Of produc.
ing tempered glass, is the principal consid
Grafton His works for producing
or bent material in plate or sheet
glass, decorated sheets Of any
desired device, enameled glass Of q very
superior quality, bottles, lamp-chimneys and
other hollow ware. A new department Il
now almost in readiness for the production
Of railway ties, nantels, architectural de
signs in various tints, foor-beans and
plates, and other large castings. All thes,
articles are from four to eight times q
strong as ordinary glass They are SO hare
that they cannot be cut with . diamond
nor will they split when slightly fractured
The Siemsns hardened glass. in fact ap
pears to occupy the same relation to ordi
nary glass that steel now bears to iron.
The processes employed by Mr. Siemen
are really simple; the difficulty has bean In
learning their proper application Fiat o.
bent articles are press-hardsned by beini
squeezed tightly, while in an almost moltel
condition, between two heavy plates o
metal The more rapid the cooling tn
harder and tougher the glass. Castings ar
made in molds which have the same con
ductivity as glass, and in every mold eac
exterior point Is at the same distance fror
the surface Of the casting. Hard-temperin
Il effected by inclosing the heated article 1
casting Of sheet-iron, equidisssnt at al
points from its surface, and cooling both te
gether. This latter process is aPplicabl
only to glass OF the same thickness through
out The articles treated by 1t are thre
times as strong as ordinary glass, and hav
found much favor among buyers.
Press-hardened glass has been adopted 70
use on the great ironclads Of the BIRTHS
navy, where the conclusion Of heavy CUR
skaters common giass, but produces n
effect upon the improved article. The stree
lights OF Dresden and Berlin are protects
by hardened glass, and are proof again
any but the heaviest missiles, the breakin
being now but one tenth what they formerl
were. Mr.. Siemens showed by experimen
that pieces Of common shsst-glass broh
whom cricket ball was dropped upon thel
from an average height OF two feet, while
blow from height Of from i've to five an
one-hslf feet was required to break Il
tempe red glass ..r
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