ALCARRAZAS, in pottery, are a kind of vessels for cooling wine or water, when intended for drinking. As they arc exceedingly porous, the liquor oozes through them on all sides; the air which comes in contact with it, by making it evaporate, carries off the heat contained in the water, Ste. in the vessel; thus the liquid remain ing in the jar continues at a temperature considerably below the surrounding atmosphere.
The peculiar convenience attached to these vessels has introduced them to numerous places of the world, where the heat renders the coolness of what is drunk greatly to be desired. Thus they are used in Egypt as well as many other parts of Africa: They are known in the East Indies, Syria, Persia, China, and in other parts of Asia; they are general in the Spanish colonies of America; and in Europe, they were introduced into Spain by the ingenious people of Arabia.
France, so nearly allied to Spain, by intercourse and by situation, and to whom the introduction of alcarrazas would be as beneficial as to the former, cannot boast of a manufactory of this article. Cit. Darzet was anxious to analyze this white marly earth, and by employing all the precision necessary for that purpose, he found that one hundred grains of it contained sixty of calcareous earth, mixed with aiumine, and a little oxyd of iron, difficult to be dissolved, and of siliceous earth, also mixed with alumine and the same oxyd. The quantity of iron may be estimated at almost a grain.
The manufactory of alcarrazas possesses recommen dations, which most others do not easily admit. The expense of forming erections for this process is very trilling. The process, by which the jars are made, as we shall sec below, is very simple; and the profits are very certain, if the public do not refuse to adopt so use ful a practice.
The preparation, given to the earth, may be reduced to three principal operations : First, Suppose it were necessary to manufacture 150 pounds of earth :—After it has been dried, and divided into portions of the size of a walnut, it is macerated in a basin or tub, by proceeding in the following manner : The workman takes about three or four Cd011inN of earth, (a celcrnin is a measure of capacity, which contains about seven pounds of grain,) which are spread out equally in the basin, and water is poured over it; he then throws in three or four celendns more of earth, which are wa tered as before, and thus repeats these operations until the tub be sufficiently full. In pouring on the last water,
care is taken not to add any more than may be neces sary to cover the whole mass. In this state, it is suf fered to remain twelve hours; after which, it is worked and kneaded by the hands in the tub, until it is reduced to the consistence of a tough paste. The earth is then deposited on a smooth flat form, covered with brick, kept exceedingly clean, over which is strewed a little sifted ashes. It is formed into a cake, about six inches in thickness, which is smoothed at the surface as well as at the sides. It is left in that state, until it begins to crack, after which it is freed from the ashes which ad here to it, and removed to another tiled place, made ex ceedingly clean.
Second Prelzaration.—To this earth, the workman adds seven pounds of sea salt, if he wishes to make jar ras; and only the half, if it is destined for the fabrica tion of botizas, or can taros. This difference arises from the greater or less capacity intended to be given to the vases; the larger the vase is, its sides must be so much thicker, that it may have the necessary degree of strength; but the earth, at the same time, must be more porous, otherwise the water would not filter through with ease; and, for this reason, the workman adds a greater quantity of salt, when he wishes to make jarras, which are much larger than the boti:as, or can taros. The earth is kneaded with the feet, adding the salt gra dually, and this labour is repeated at least three times, without the necessity of adding more water, as the mois ture retained by the material is sufficient.