PERHAPS there is a greater demand for fire-resisting than for thief-resisting safes, and certainly it is in the former character that they are most often put to the test. The consideration, therefore, of what is the best form of construction to cope with fire is most important; while it is also a much simpler matter than when strength against thieves is required.

In fire we have an element whose character is known, and which cannot attack us in some new way for which we are not fully prepared. All that it can do to a safe is to exercise upon it a certain heat, the intensity of which may be pretty nearly determined, and which cannot in actual practice last beyond a certain time. Probably heat that will melt iron in a large mass is seldom produced in the burning of an ordinary dwelling-house; but in a warehouse with inflammable contents such fierce heat often exists, so that a safe should be proof against it for two or three hours. Unless a safe were very bulky it could not well preserve its contents without any damage for a much longer time; and indeed it is not necessary, for no safe is very likely to be exposed to an intense all-round fire longer than three hours; by that time it will either have fallen into rubbish, or the dÉbris from above will have covered it in, and protected it from immediate contact with the fire. It will be seen from this that it is advisable not to build a safe partially into a wall or recess; the chances being that it will be kept in its place long enough to have the full force of the fire expended upon its exposed portion, and then fall a greater distance and upon harder material than if it had fallen when the wooden floor first gave way.

The first quality that a fire-resisting safe should possess is strength in its construction sufficient to prevent its being damaged by a heavy fall, or sustaining injury through the plates warping from heat. This cannot be obtained unless the outer plates are at least a quarter of an inch thick (or upwards, in big safes), strongly joined at all the edges by stout angle-irons well rivetted to them. Other and more expensive methods are used to join the edges, and are doubtless better than the foregoing; but this is at once a cheap, effectual, and most generally used method.

Secondly, it is essential to make the safe as nearly airtight as possible, to do which it is only necessary that the door should fit very closely at its edges, and that its inside face touches at every possible point the interior of the safe.

The third thing to be considered is the fire-proofing—the most important feature of the safe. Almost everything that one can think of has been either proposed or used for proofing—water, wood, paper, plaster-of-Paris, chemicals of all sorts, and many other things besides. But of all these what may be termed a combination of water and wood, in the forms of alum and sawdust, has been most extensively used.

There are two walls of wrought iron in the safe, and the intervening space has to be filled with a fire-resisting material, which may be either of a refractory nature, such as fire-clay, sand, or any other practically infusible slow conductor of heat; or it may be an absorbent substance containing chemicals that will evolve moisture when heated. The former of these two methods is now seldom used except by makers of cheap common safes, who sometimes use clay, ashes, or mould. The evaporating system is generally adopted, and as a rule the absorbent material is common sawdust, with which is mixed ordinary alum, the water of crystallisation in the alum being gradually parted with under the continued heat generated by fire. Mahogany sawdust is preferred, as being less combustible than that of white woods.

At one time tubes of glass or fusible metal containing alkaline solutions were imbedded in the sawdust and were supposed to burst or fuse at a given temperature, but it was found that the glass accidentally broke or the fusible metal became corroded, and allowed the liquids to escape, thus damping the contents of the safe. But the mixture of alum with sawdust is open to two objections. Owing to the hygroscopic nature of sawdust the alum is liable to decomposition, thereby producing a certain moisture in the safe; and, secondly, there is of course a limit to the production of moisture from the alum when under the action of fire, after which the sawdust will become gradually dry, and although it may not actually ignite, it will become charred, and even red hot, under sufficiently continued heat. It is but fair, however, to say, as I have previously suggested, that such instances of continued heat are but rarely probable; yet, for the before-mentioned reasons, I prefer and use an incombustible material, very light and absorbent, and which does not possess the bad qualities of sawdust, but which is more expensive. Supposing the alum to become exhausted, there still remains the protection of a substance which is both infusible and a bad conductor of heat.

Of course the actual amount of resistance to fire depends largely on the capacity of the proofing chambers. When advisable the thickness of these may be increased to any extent desired, or the safe may have several chambers, all containing proofing, or intermediate ones left as air-chambers only.

To sum up the qualities which are requisite to make a safe proof against an ordinary fire, it must, first, be made entirely of wrought iron; secondly, the outer plates must be at least a quarter of an inch thick; thirdly, there should be a space of three to four inches all round it of an evaporating non-conducting composition. With such a safe as this, properly put together, the general run of fires may be defied; but there are cases where extra precaution should be taken, and the safe kept in a brick, stone, or iron strong-room. No safe inside a strong-room has, to my knowledge, ever been destroyed; but many—always light ones—in warehouses or offices have had their contents burnt.

And here I would caution those not acquainted with the subject to put little faith in the tests, either public or private, that are sometimes made, unless they are conducted by persons quite disinterested. When it is done in this way of course the result is one that may, if certain conditions are fulfilled, be valuable; but so frequently are these ‘tests’ arranged, either by making a safe specially for a trial, by carefully packing its contents, or by constructing the fire in a particular mode, to turn out such wonderful successes, that it will be well not to rely upon anything but actual experience gained from the result of safes which have been known to be subject to an ordeal in the ordinary course of things. Plenty of such instances can be investigated, but it will obviously be unadvisable to give here the numerous results that have from time to time been chronicled by the daily papers and other publications.

It should be borne in mind that certain things are less liable to injury from heat than others; and therefore it is that books will sometimes sustain no injury, whilst loose papers in the same safe may be more or less damaged. For this reason it is advisable that all parchments and papers be kept in a drawer or cupboard of a safe, as the second enclosure (though with no more fire-proofing round it) gives a slight extra security.

Another caution I would give is that, after being in one fire, a safe should not be relied on to resist fire again until it has been examined and re-proofed by the maker or a thoroughly competent person. The resisting properties are certain to be damaged, if not destroyed altogether; and although I know of safes still in use that have not been renovated since preserving their contents, I would not place any faith at all in their power to prove again successful.

The destruction of the Pantechnicon has presented an opportunity of fairly ascertaining the effect of great heat upon various safes, and, strange as it may seem, scarcely one of the many safes survived the conflagration without injury. One French safe had nothing but its four sides left intact, its front, back, and inside having disappeared as if driven out by a cannon-ball. The cast-iron safes, of which there were several, proved, as might be expected, utterly useless, being found when pulled out of the ruins twisted into all sorts of shapes, or cracked and broken like glass. Other safes, by makers whose reputation can hardly be affected by damage done in such an unprecedented fire, had their contents very seriously injured; and only a few safes came out of the trial in at all a satisfactory state.

Speaking of French safes, I may here say that, as a rule, they and most of the Continental safes cannot be trusted in English fires, nor against the more advanced skill prevailing among our English thieves. Without offence their character may be summed up as being really ‘French’—pretty in outward appearance (which is more than can be said for our safes), with peculiar locks requiring no keys, and certain other un-English things about them; they are quite unsuitable for our market, and vice vers our British safes find little sale in France.

Safes and other receptacles to contain gunpowder and preserve it from explosion have recently been talked about; and there is no doubt that one result of such a calamity as the late Regent’s Canal explosion will be to expedite legislation on the subject of the transit and storage of gunpowder and other explosives. It may appear curious that gunpowder can be preserved from damage by fire with much greater ease than such a substance as parchment, but the former can only be destroyed by being in contact with actual fire, or becoming subject to a most intense heat (about 560 degrees); while a moderate heat or exposure to steam, such as is necessarily generated by the fire-proofing of a safe, often irretrievably damages parchment. A well-made safe, on the principle of evaporation already described, may be relied on to preserve gunpowder from considerable heat, but to avoid the possibility of flame or sparks entering the space round the door, a second safe of lighter make may be placed inside the ordinary one. Major Majendie, in a recent report to the Government on this subject, suggests that there should be public trials by the various makers, of safes, such as they severally think most suitable for this special purpose. It remains to be seen if this advice will be followed, and if so, upon what principle the trials will be conducted, and whether the safes or chests so tested will be precisely the same as the makers intend to retail, or are made specially for the occasion. It is extremely doubtful if the Government would be acting wisely in affording facilities at the public expense for private firms to experiment with safes the merits of which are pretty well known; but should the trials take place, no doubt the results will, in some instances, be of a nature to astonish those not practically familiar with the action of fire in such cases.