Morning journal and courier., 1880-11-12
The History of Ffre-PrOOf Safes. From the Boston Herald

In regard to the invention of fire proof safes in America, the accounts have are conflicting. It is said that something over fifty years ago the discovery was made by me- chanic who attempted to boil water in a kettle that was covered with plaster paris He found that it was almost impossible to heat the water to a boiling point and concluded that plaster of paris, therefore, was great non conductor of heat. In relation his experience to several there probably among them some one who conceived the idea of applying it to ire-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 sub- stance for filling kept its place until about fifteen years ago, when 1t was generally given up. The reason for adandoneding the use of plaster is thus given. It was used not in it's dry state but mingled with water, and allow ed to set after being poured in between the castings. This filling, it was found, attracted moisture from the atmosphere and either produced oxidation of the metal in contact, or formed sulphuric acid of strength enough to corrode the iron. It 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 th9 set plast- CT was corroding the metal, 1t thought dry plaster might do, but though poor conductor of heat it was found defective in having no water to give off, and alum, which contained a large percentage of water, was mixed with 1t and found to answer the pur- pose very we'll
 Some twenty years ago before the of plaster as a filling was abandoned, the use of hydraulic and other cements WAS commenced. The cement was simply mixed with water and put in to set in the same way as plaster. The property of the absorbing water varies with the different kinds of cement, but that variety which absorbs the most water is ob- vioysly the best fitted for filling purposes. Some kinds of cement will absorb one third to one half their volume of water, while there is kind which, it is said, will absorb an equal volume of water, that is, barrel of cement will absorb barrel of water. Ce- ment at the present time seems to be the favorite filling with most safe makers and it is found not to corrode the iron on account of the alkali which is in it, which has pre- servative tendency on that metal Pure ce ment is used by the best safe makers, though it is said some mix in sand, which injures the filling, and destroys to an extent its non-con- ducting properties. Asbestos has been used, but was found to be not good non-conduct- or, and was soon abandoned.
 About twenty years ago Boston man took out patent to line safe doors and hanges with soapstone but in practice 1t was found, that, in a long continued fire, the soapstone heated to very high temperature and tained it's heat, so thatit in turn was abandoned. In 1860 a patent was taken out fer the attach ment of the plaster filling to plates suspend ed between the walls, so that in shrinking it's diminished size will not permit its falling from its place patents were also taken out for the use, for filling, of pure alumina; and also, for the same purpose, of sulphate of iron mixed with plaster paris. In 1863 the following patents were taken out: For the construction of Q safe two air and steam tight castings, one within the other, and with the intermidate spaces filled with material capable of generating steam under high heat, the latter melting fusible plugs in the outer casing to permit the exit of the steam also for the use of filling made of plaster paris set with solution of starch also for fill ing formed of a compound of calcined and powered gypsum and alum in pieces embed ded in the plaster in such relative proportions that the water of specialization in the alum evolved by heat shall set the plaster(t this was the alum safe already alluded to); also for the furnishing of the filling with cavities to prevent the rupture of the parts from the expansion of the moisture by freezing. In 1864 patent was taken out for filling of alum in small Jumps rolled in plaster and then imbedded in dry clay. In 1865, fill ing of epson salts, either alone or combined with sulphate of lime, was obtained.