Daily Honolulu press. [volume] (Honolulu, Hawaiian Islands) 1885-1886, 1885-10-28
TEMPERED GLASS.
RESULTS ATTAINED BY A DRESDEN
MANUF
The Toughcnipg Process Of De la Bsstic
and Its Faiiure--sr Frederick sis-
mems Methods - Hardened
Glass by simple Processes
PHILADELPHIA Record.l


When piece OF ordinary glassware is
blown or cast in mold the subsequent cool
ing process does 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 popular syn
ony N for weakness and unreliability, and 1t
has long been tho most formidable obstacle
TO a proper development Of the glass manu-
factoring industry. For many years glass
makers have sought for some process by
which glass might be made as stout as cast
iron and as hard rs its original quartz,
while retaining the plability I'm manufnct-
ure that has made 1t 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 as iron and Of
but one fourth its weight and susceptible of
an almost infinite variety OF decoration,
would unique stionably be a new and Inn
portant resource in the hands Of civilian
ton.
In their search for this new material the
glassinakers have not boon entirely unsuc-
cessful, although the result of their labors
up to this time is shown only by q few frag-
msntary wares which have hardly attracted
public notice. The way to success Is difficult
aud new chemical compounds, independent
of present manufacturing processes may DO
required before the desired end 10 attained.
The tonghening process Of De la Bastie,
which promised so much ten years ago, has
dropped into allegiance. and nothing useful
Is anticipated from it in the future. 1t con-
sisted imply in heating the glass and
plunging 1t Immediately into hot oil. The
articles thus toughened were always liable
10 break spontaneously into fragments; but,
generally speaking, unless broken very loon
they would last long time.
But thi, process presents many difficult
ties. 1t Is not adapted I, all forms of glas
manufacture, and the percentage Of loss by
breakage Is very large. The cause Of the
breakage Is inherent in the operation itsel
which cools the articles in proportion to
their surfaces instead OF in proportion to
their bulk, and thus induces molecular
strain likely ar any time to cause complete
rupture This commercial objection. to
l,ether with the difficult and uncertain
character OF the process, has prevented d.
la Baste's method from producing a sensi-
bic impression upon the glass manufactur-
ing process OF the world. Like many other
clever novelties, it has been interesting from
scientific standpoint but failure COM
meroially.
But II Do Ia Bastie has failed In attaining
his object, he has at least pointed the way
through which others may reach tho prize.
Six years ago Frederick Semens, then al
ready of established reputation as a prac-
tical scientist and man OF affairs. began at
hi Dresden glass-works the production by
original processes OF toughened, or, as he
profera to call 1t, hardened glass. The value
Of his output Tor the first year was $1,000
and there has been steady annual increase
until last year IL amounted TO over $35, 900
Mr.. S!emens describes his method at
length In paper which he recently read
before tho London Society OF Arts They
include three distinct processes-pyess-
hardening. casting and hard -tempsring--
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 oil
heating and cooling every portion of the ar
tcle 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 1t has been found
somewhat difficult TO attain the require
theoretical perfection: but this Is not 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 consii
GRAFTON. His works for producin
hardened glass already furnish fat
or bent material in plate or sheet
glass, decorated sheets OF any
desired device, enameled glass Of very
superior quality, bottles, lamp-chimneys an
other hollow ware A new department /
now almost In readiness for the production
Of railway ties, mantels. architectural de-
signs In various tints. door-beams an
plstes, and other large castings All the {
articles are from four to eight times
strong as ordinary glass They are so hari
that they cannot be cut with damon I,
nor will they split when slightly fracture 1.
The Siemens 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 besn In
learning their proper application. Flat OF
bent articles are press hardened by being
squeszed tightly, while in an almost molten
condition, between two heavy plates ol
metal. The moro rapid the cooling tbs
harder and tougher the glass Castings are
made In molds which have the same con
ductivity as glass, and In every mold eact
exterior point Is at the same distance from
the uriaco OF the casting. Hard -temperuu
IL effected by incloslng the heated article
casting OF sheet-iron, equidi,tant at all
points from it's surface, and cooling both to
gether. This latter process is Applicant
only to glass OF the same thickness through
out Tie articles treated by 1t are three
times as strong as ordinary glass, and hav
ionni much favor among buyers.
Pic hardened glass has been adopted foi
use on the great ronclads Of the British
navy, where the conclusion of heavy gun
shatters common glass, but produces ne
OBJECT upon the improved article. The stree
lights OF Dresden and Berlin are proteo tet
by hardened glass, and are proof again
any but the heaviest missiles, the breaking
being now but one-tenth what they formerl,
wore Mr.. Semens showed by experiment
that pieces OF common sheet-glass brokI
when cricket ball was dropped upon then
from an average height OF two feet, while
blow from height Of from FIVE to five an,
one-half feet was required to break tn
iempere glass
Growth Of Cereals.