Hitherto the question of packing delicate goods has been viewed almost entirely from what may be called the strength-of-materials standpoint. Manufacturers and importers have found that ordinary packing material of a certain thickness and weight was sufficiently strong to withstand the blows received in transit, and have forthwith adopted this as the only condition necessary to be fulfilled in their packages, unless, indeed, anything cheaper should come into the market, in which case most probably it would be used instead. There is one exception to this which has recently occurred. During the last few years there has been a decided increase in the demand for tastily and attractively packed goods - goods of all kinds, in fact, put into such packages that the eye of the purchaser should be attracted by the appearance. The natural result of this has been the employment of any and every material which was adapted to increase the ornamentation, regardless of whether it was adapted for preserving the contents from injury.
Packages in which wood is used have given the worst illustration of this erroneous style of packing, green wood being frequently employed, partly, perhaps, because of its working more readily, and woods which either have or develop an unpleasant odour being used because of their pretty markings or suitable colour, while it has not been uncommon of late to employ some kinds of wood which are to a certain extent absorbent, and retain any smell with which they come in contact.
Where goods of an oily or greasy character have to be packed, and the escape of the oil may to a considerable extent be attended with the risk of fermentation or rancidity, grease-proof paper, or some such packing has to be used, and up to the present this paper is unsatisfactory in character indeed, unless very costly kinds are used. In considering the question of export goods, we have, at the outset, to face the fact that goods stowed on board ship have necessarily to be packed in the hold, and to remain there for some time - it may be for weeks or even months - and that wherever the voyage may be to it is almost certain that the temperature to which they are subjected in the hold during nearly the whole time is far in excess of our ordinary English atmospheric temperature. To this must be added another fact which has a great bearing on the question, and that is that the atmosphere of the hold of a vessel is saturated with moisture, and very frequently supersaturated. Bilge water exists in small quantities in every vessel.
Almost every cargo contains goods in such a state of moisture that they are capable of giving off moisture when the temperature is raised, and there can be few circumstances under which the air of a ship's hold, when the latter is stowed with cargo, will contain less than the full saturation amount of moisture. But the temperature of the hold must vary from time to time, very slightly, it is true, hut probably a small diurnal variation of some 1° or 2° would generally appear. As soon as the diurnal, or perhaps more probably nocturnal, fall of temperature takes place, moisture in the form of dew or cloud would be produced and deposited upon the goods. This is not theory only, but a fact which has been noted in numbers of cases, for the moisture so deposited is always first found upon the top or upper surface of the packages. There is a great deal of importance in this saturation or supersaturation with moisture. Dry air has very little effect upon most natural products beyond a certain amount of desiccation, and its action upon metallic substances is very slight. Most air, on the contrary, acts rapidly and energetically upon metallic bodies, and is the most active agent in setting up decomposition in organic bodies.
This is not merely a surface effect, but depends upon the specific capacity which almost all organic substances appear to have for water. Leather, wood, tea, bark, straw, each absorb a certain definite amount of moisture corresponding to the variety of the article itself - not merely its species but its variety - and the moisture of the air in which it is placed. Thus, in the case of, say, 4 samples of tea, of four different kinds, if exposed to air saturated with moisture they will absorb more moisture than they previously contained, but when again exposed to air in what may be called its normal condition in this country - that is, not saturated - the excess of moisture absorbed would be given off again, and while this excess is escaping into the atmosphere it may carry with it some of the aroma belonging to the goods themselves. Nearly everybody would admit that the alternately heating and cooling of any article with a delicate smell would injure that smell either in quantity or quality, or both, but it is equally true that alternately moistening and drying such an article - in other words producing such an effect as would be obtained by an exposure alternately to a supersaturated atmosphere and to an atmosphere not saturated with moisture - would have a like effect.
Dealing still further with the exterior of the package, this deposition of moisture in the form of dew on the exterior has another important effect. This water is precipitated in the air in the form of minute, almost infinitesimally small, water globules, and these have a strong solvent action on any gases or vapours which are present in the air, and which are thus in a more active condition when brought in contact with the goods on which the dew falls. Suppose the air in the hold of a ship to be impregnated, as it always is, with carbonic acid, and also slightly saturated with acetic acid generated from some source or other - the dew deposited on any change of temperature will become saturated with both carbonic and acetic acids, and will obviously be a dilute acid in the most suitable form for acting upon any metallic surfaces with which it comes in contact. Not only so, but leather or cloth goods may be rotted by such an action during a long voyage, and the causes may erroneously be put down to sea damage.