Juniata sentinel and Republican. [volume] (Mifflintown, Juniata County, Pa.) 1873-1955, 1880-12-01
History OF Ffre-Proof Safes.

In regard 10 the invention of frc-proo
cafes in America, the accounts we have ar,
conflicting. II is said that something owe
fifty years ago the discovery was made b,
mechanic who attempted to boil water il
a kettle that discovered with plaster of paris
He found that it was almost impossible tc
heat the water to boiling point, and con
cludcd that plaster Of paris. therefore, wa,
a great non conductor of heat. In relating
his experience to several there probably
was among them some one who conceived
the idea of applying it to fre-proof safes.
After this discovery little, if anything, was
used in this country for filling safes but
plaster for about twenty five or thirty years.
This substance for filling kept its place
until about fifteen years ago, when it was
generally given up. The reason for aban-
doning the use Of plaster is thus given. II
was used not in its dry state but mingled
with water, and allowed TO set after being
poured in between the castings This fill
ing, it was found, attracted moisture from
the atmosphere and either produced oxida-
ton of the metal in contact, or formed
sulphulc acid OF strength enough 70 corrode
the iron. IL is not an uncommon thing to
find old safes that were filled in this way
with holes eaten through their panels
When it became apparent that the set plas-
ter was corrodine the metal, 1t was thought
that dry plaster might do. but, though a
poor conductor of heat, it was found defec-
tive In having no water to give Oft, and
alum, which contained a large percentage
Of water, was mixed with il and found TO
answer the purpose very well. Some
twenty years ago before the use Of plaster
rs filling was abandoned, the use of
hydraulic and other cements was commen-
ced. The cement was simply mixed with
water and put in TO set in the same way as
plaster. The property of absorbing water
varies with the different kinds of cement,
but that variety which absorbs the most
water is obviously the best fitted for filling
purposes. Some kinds Of cement will
absorb one-third to one half their volume
81 water, while there is kind used which.
it is said, will absorb an equal volume Of
water, that is, barrel of cement will absorb
barrel of water. Cement at the present
time seems to be the favorite filling with
most safe-makers, and it is found not 10
corrode the iron on account Of the alkali
tendency on that metal. Pure cement is
used by the best safe-makers, though it is
said some mix IN said, which Injuries the |
filling, and destroys 10 an extent its non |
conducting properties. Asbestos has been |
used, but was found to be not a good I
uon-conductor, and was soon abandoned. |
About twenty years ago Boston man took |
out patent to line safe doors and flanges /
with soapstone, but in practice it was
found that, IN a long-continuei fire, the |
soapStone heated 10 very. high temptra-
tufe and retained its heat, so that Ii in turn
was abandoned. In 1850 q patent was |
taken out for the attachment of the plaster
rlling to plates suspended between the |
walls, so that in shrinking its diminished
size will not pernit its falling from its
place; patents were also taken out for the
use, for filing, of pure alumina; and also,
for the same purpose, of sulphate of iron
mixed with plaster of paris. In 1853 tine
following patents were taken out: For the
construction Of safe with two air and
steam tight casings, one within the other,
and with the intermediate spaces filed in
With material capable of generating steam |
under high heat, the latter melting fIlsi-I
bic plugs in the outer casing 20 per-
init the exit Of the steam; also for the use
OF filling made of plaster of paris set with a
solution Of starch; also for filing formed
OF compound Of calciued and powdered
gypsum and alum in pieces embedded In
the plaster in such relative proportions that
the water of crystallization IN the alum
evolved by heat shall set the plaster (this
was the alum safe already alluded to) also
for the furnishing of the filing with cavi-
ties to prevent the rupture Of the parts
from the expansion of moisture by freezing.
In 1864 a patent vas taken out for fill
ing of alum in small Jumps rolled in plaster
and then imbedded in dry clay. In 1865,
a filing of epson salts, either alone or COM
Dined with sulphate of lime, was obtained.