Of the various forms of adulteration practiced in China and Japan artificial coloring or “facing” is perhaps the most prevalent and glaring. The material used for the purpose is usually composed of Prussian blue, gypsum, indigo, turmeric, and more frequently, China clay, a whitish iridescent powder, resembling mica, variously composed, but generally consisting of kaolin (soapstone), and sulphate of lime. While that in use in Japan is not known, its composition being a secret, known only to the manufacturers, but is evidently a preparation of gypsum and kaolin, the Japanese contending that it is a vegetable compound pure and simple. That kaolin is used in its preparation can hardly be denied, as kaolin contains sulphur, and many of the lower grades of Japan teas are found on infusion to possess a slightly sulphurous odor. It has been proved, however, whatever its nature, to be less harmful and injurious than the Chinese compound, and used only in the manipulation and sophistication of the lower or commoner grades of tea in that country.
The process of coloring or facing Green teas is performed by placing a portion of Prussian blue in a porcelain bowl, not unlike a chemist’s mortar, and pulverizing it into a fine powder, a small quantity of gypsum being meanwhile burned over a charcoal fire, to soften it, after which it is ground fine. The two substances are next mixed together, in the proportions of one part blue to four parts gypsum, both making in combination a light-blue preparation, in which state it is applied to the leaves during the last process of firing, about five minutes prior to removal from the pans, the time being regulated by a burning joss stick. The Saihoo taking a handful of the compound, scatters it over the leaves while in the pans, other operators tossing and turning the leaves around rapidly with their hands meantime in order that it may equally diffuse among them. One ounce of coloring-matter will face fifteen pounds of leaves, imparting to them a dull leaden-blue hue, and “glossy” or greasy appearance, readily detected in the hand. In many districts, most notably in Ningpo and Canton, turmeric, kaolin, and China clay are more extensively employed for the purpose. This almost transparent form of adulteration is readily detected in the following manner:—
(1) When the tea is heavily coated it may be easily recognized by its dull leaden-blue color and greasy appearance in the hand, or by placing a small quantity of the leaves on a piece of glass or smooth table, on removing them the coloring-matter will be found adhering to the hands, glass or table, and its nature, whether Prussian blue, turmeric, kaolin or indigo, readily determined with the aid of a microscope. (2) When only lightly colored or suspected, place a sample of the leaves in a cup or wine-glass and pour on briskly boiling water and stir well for two or three minutes, then strain well through a thin muslin cloth. The coloring-matter, if any, will be found adhering to the cloth, that passing through, sticking to the sides, or forming a sediment at the bottom of the vessel into which it is strained. If these deposits be treated with a preparation of chlorine, or a solution of chloride of lime, and turn white, the coloring substance used is indigo. But if treated with a little potash, and it becomes brown, it will prove to be Prussian blue, the application of a little sulphuric acid having the effect of turning it blue again.
What are known to trade as “Canton Green teas” are made from tea-dust and exhausted leaves ground up fine and aglutinized with a preparation of gum, glue or other starchy substance to unite and hold them together and then artificially colored or glazed. This fabrication is readily detected by crushing the so-called leaves between the fingers or rubbing them between the hands, upon which they leave a yellowish-brown stain, greasy in nature. Or by powdering a small quantity of the alleged leaves and treating the dust with a dilution of sulphuric acid it becomes very much discolored, and if it assumes a leaden-blue color on the application of caustic potash it is colored with Prussian blue. Again, place a small quantity of the leaves in a cup or glass and pour on boiling water, they will immediately begin to disintegrate and form a thick, gluey deposit at the bottom of the vessel. By treating this precipitate with a little iodine the mass will become separated and dissolve into its original dust.
FOREIGN OR SPURIOUS LEAVES IN TEA.
Another reprehensible form of adulteration is the substitution or admixture of foreign or spurious leaves obtained from other plants, which resemble in structure but differ widely in character from the true tea-leaf, such as those of the willow, plum or ash. Millions of pounds of these leaves are annually picked, cured and colored in the same manner as tea in China, and used for the purpose of increasing the bulk and reducing the cost, while in England, particularly, the leaves of the birch, elm, willow, chestnut, poplar and hawthorne have been extensively used for the same purpose. The coloring material used in the latter country differs from that used in China and Japan being still more dangerous and injurious to health. This form of adulteration, however, is trivial when compared with the former one, but, nevertheless, the expert and analyst are frequently called upon to deal with it to a much greater extent than most people imagine.
Such foreign leaves in tea may be best detected by their botanical character or by the absence of the special structural marks which distinguish the genuine tea-leaf from that of all other leaves in the vegetable kingdom, for while the true leaf bears a strong resemblance to that of the willow, ash and plum, it varies, however, in size form and structure. The border of the true tea-leaf is more regularly serrated, the serration stopping just short of the stalk, and the venations are very characteristic, the veins running out from the mid-rib almost parallel to one another, but altering their course before the border of the leaf is reached, and turning so as to leave a bare space just within the border of the leaf. So that in making an examination of a sample of tea for the purpose of ascertaining whether these distinctive characteristics are present in the leaves under treatment, it will be found convenient to pour hot water on them so as to soften, uncurl and spread them out more easily, as otherwise considerable difficulty will be experienced owing to the brittleness of the tea-leaves in the dry state.
TRUE TEA-LEAVES.
