Coffee and chicory

by P. L. Simmonds

The worth of coffee as an article of commerce is lessened in proportion to the extent to which these progressive changes are allowed to go on. If heating has taken place, the bean can never afterwards acquire the pellucid colour which is indicative of well-dried coffee, but partakes more or less of a dingy appearance. If mouldiness ensues, the aromatic properties, like those of tea, give place to an insipid flavour; and finally, if the bean undergoes putrefaction, it assumes a dull black colour, and becomes totally destitute of every valuable property.

When the crops ripen, they must be gathered and cured under all circumstances of weather; and as it generally happens that this has to be done during the prevalence of the periodical rains, the difficulties to be contended with are so much the greater. The extensive nature of the operations has also to be taken into account in forming an estimate of the difficulties to be provided for. During the busy season of crop upwards of 1000 bushels of cherries are daily gathered from some plantations, yielding an increase of 500 bushels of parchment coffee to be daily added to that which has already accumulated in the store.

Past experience having shown that coffee was most easily preserved in a sweet state when spread thinly on the floor, large and commodious buildings were called into use, notwithstanding the unusually heavy expense which attended their erection in situations remote from town, where sufficiently skilful labour was only to be had at the time, and with great difficulty. On this account inadequate accommodation was provided on many plantations, and the coffee accumulating to a considerable depth, no amount of hand-turning could keep it from contracting a musty smell, its proneness to decomposition increasing greatly in proportion to the extent of the accumulation.

Some years ago it occurred to Mr. Clerihew that it was possible, by means of fanners, working on the exhausting principle, so to withdraw air from an enclosed space as to establish a current of air through masses of coffee spread on perforated floors forming the top and bottom of that space. This plan he carried into execution at Rathoongodde plantation, and it has since been adopted by many planters.

The following is a detailed description of Mr. Clerihew’s invention, a model of which was shown at the International Exhibition of 1851:

The water-wheel is an overshot one, nine feet in diameter, and is of much smaller dimensions than any wheel that has hitherto been employed for pulping. It is, however, sufficient in power to work the fans and pulpers simultaneously, the excess of its power over that of other wheels being gained by the diminution of friction consequent on there being no intervening shafting and gearing. The entire wheel is constructed of wood, with the exception of the shaft, which is unusually light, as it has merely to serve as a support to the wheel. By means of a double band rim-bolted to the arms on each side, motion is given to the pulpers from the one and to the fans from the other.

The floors of the curing-house are laid with laths 1¼ inch square and 2 inches apart; these are covered with open coir matting; being rather cheap and durable, this material answers the purpose remarkably well. The side walls of the curing-house are constructed in the manner of the country, viz. of wattled work filled in with clay and smoothed over so as to be air-tight.

To derive the full benefit of natural heat, the roof is covered with felt or with sheet-iron, so that in fine weather the temperature of the air in the upper floor is raised considerably by contact with the hot roof, and its capacity for absorbing moisture much increased, preparatory to its being drawn down through the mass of coffee in the upper floor. Even in the cool climate of the district of Upper Hewahette, at an elevation of 4500 feet, in a fine day the temperature of the air under a felt roof is 120° when the fans are not working, so that a great drying power is thus made available at no expense.

The lower floor, on the other hand, is adapted for the application of artificial heat for the purpose of evaporating the surface water from each separate batch of coffee as it is taken from the washing cisterns preparatory to its being deposited in the upper floor. In wet weather this is essential, for the atmospheric air being then saturated with moisture, no drying can take place until its capacity for absorbing moisture is increased by an increase of temperature. One other reason for adopting this arrangement is, that when the coffee is first taken wet from the washing cisterns the interstices of the beans are more or less occupied with water, and thus present a medium less pervious to air than is the case when the surface water has been dried off. Consequently it is desirable that, until this has been done, the depth of the coffee should not exceed six inches, and, to be equal to every emergency, the heating power ought to be sufficient in the wettest weather to evaporate the surface water from the produce of a day’s picking (within twenty-four hours), so as to allow of its being removed into the upper floor. The daily number of bushels picked from any, or the same plantation, is of course a variable quantity: depending on the extent of the cultivation, the quality of the trees, the number of hands employed, and the elevation of the land; the latter, when considerable, having the effect of prolonging the picking season. The stove is more than sufficient for a daily picking of 400 bushels of cherries.

The heating stove is square, has a waggon head with a semicircular opening in the centre for the passage of air, and is constructed of stout sheet-iron. It is placed within an arch, with a clearance of nine inches all round also for the passage of air, the guiding principle in its construction being to adapt it to the burning of wood, and to expose as much heating surface as possible to the air which flows past it into the air-chamber beneath the ground-floor. The stove opening is the only one which admits air to the coffee on the ground-floor. Consequently, when it is more or less closed by a damper, the power of the fans is exerted either in part or altogether on the mass of coffee in the upper floor.