The Palatka daily news. (Palatka, Fla.) 1884-1888, 1885-10-11
TEMPERED GLASS.
RESULTS ATTAINED BY A DRESDEN
MANUFACTURERS.
The Toughening Process of DE la Bastis
and Its Failure-Mr. Frederick Sie-
mems Methods = Hardened
Glass by Simple Processes
Philadelphia Record. ]


consequently thrown into a state of tension
or strain. The brittle quality resulting from
| this condition has become popular sym
| ony m for weakness and unreliability, and 1t
| has long been the most formidable obstacle
| to a proper development of the glass manu-
| featuring industry. For many years glass
| makers have sought for some process by
| which glass might be made as stout as cast
| iron AMI hard It's original quartz,
| while retaining the piiabIlity IN manufact-
ure that has made it thing Of universal
| use and necessity. Such discovery would
be followed by many important changes in
| manufactures in architecture, and in many
oi the appliances and implements of daily
life. A material "a strong n iron and of
but one fourth its weight, and susceptible of
| an almost infinite variety Of decoration,
would unique stionably ba a new and inn
| pOrtaut resource in the hands of civilian
| ton.
| In their search for this now material the
| glasSmaker5 have not been entirely unsuc-
| cossfuI although the result of their labors
| up to this time is shown only by a few frag-
mentary wares, which have hardly attracted
public notice. The way to success is difficult,
and new chemical compounds, independent
of present manufa curing processes, may be
| required before the desired end is attained.
| The tonghening process of De la Bastie,
| which promised much ten years ago, has
| dropped into abeyanco and nothing useful
| is anticipated from it in the future. 1t con-
| sisted simply in heating the glass and
| plunginS it mme lately into hot oil The
| article: thus toughened were always liable
| to break spontaneously into fragments; but,
| generally speaking unless broken very soon
| they would last a long time
But this process presents many dliIicul-
| ties. 1t is not adapted t. all forms of gla-S
| manufacture and the percentage of loss by
hreakage is worry large. The cause of the
| hreakage a. Inherent IN the operation itself,
| which cools the articles in proportion to
| their surfaces instead of in proportion to
| their bulk, and thus induces 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 Baste's method from predicting Il seHsi-
| bic impression upon the glass manufactur-
| ing process Of the world Like many other
| clever novelties, it has been intere ting from
a scientific standpoint, but a failure COM
| mercially.
| But if De la 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 prac-
| tical scientist and man of affairs, began at
hi Dresden glass works the production by
original processes of toughened, or, he
| prefers to call it, hardened glass The value
| of his output for the first year was $4,000,
| and there has been a steady annual increase
| until last year it amounted To over S35, 600.
MIR. Siemens describes his method at
| length in paper which he recently read
| before tho London Society of Arts. They
| include three distinct processes-press-
| hardening, casting, and hard comparing
| and all these arc 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 fr
| ticle shall be of exactly the same tempera-
| ture. The devices to secure this end are
| varied according to the various shapes to be
| treated. In practice it has been found
| some what difficult to attain the required
| theoretical perfection; but this is not n 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 produce
ing tempered glass, is the principal consid :
GRAFTON. His works for producing
hardened glass already furnish fiat
| or bent material in plate sheet
| glass, decorated sheets of any
desired device, enameled glass of very
superior quality, bottles. lamp-chimneys and
| other hollow ware department Is
| now almost I'm readiness for the production
| of railway ties, mantels, architectural de-
| signs in various tintS, fOor-beams and
plates, and other large castings. All these
| articles are from four to eight times as
| strong "a ordinary glass. They are so hard
that they cannot be cut with q diamond,
nor will they split when slightly fractured.
The Siemens hardened glass. in fact, APP
| pears to occupy the same relation to ordi-
| nary glass that steel now bears to iron.
The processes employed by Mr.. Siemens
are really simple; the difficulty has been in
| learning their proper application Flat or
| bent articles are press-hardened by being
! squeezed tightly, while in an almost molten
condition, between two heavy plates of
metal. The more rapid the cooling the
| harder and tougher the glass Castings are
| made in mods which have the same con-
ductivity as glass, and in every mold each
| exterior point is at the Same distance from
the surface of the casting. Hard-tempering
| is effected by inclosing the heated article i'll
| n casting of sheet-iron, equidiStant at all
points from its surface, and cooling both to-
| gether. This latter process is applicable
| only to glass Of the same thickness through
| out. Tie s..Iirles treated by it are three
times as strong ordinary glass, and have
| found much favor among buyers.
Pro IS hardened glass has been adopted for
use on the great ironclads of the British
| navy, where the cnncuSsion of heavy guns
| shattera common Isla -, but produces no
effect upon the improved article. The street
light Of Dresden and Berlin are protected
| by hardened glass, AMI arc proof against
| ANY bat III heaviest missiles, the breaking
b.Ins .i,,y bat oiia- tenth what they formerly
were hIr S;emons showed by experiments
that pieces of common sheet glass broke
when a cricket ball was dropped upon thsm
from an as.'rase height of two feet, while a
blow from a nei,,nt of from five to five and
one-h half feet was required to break the
tempe red glass
| The Unrest Grows