Manganese Bronze (Manganese Brown, Bistre).—There is one good mineral color, however, which came into use early in the last century and which, while hardly ever used by professional dyers, is of interest to craftsmen. This color, in its chemical composition, greatly resembles the iron buff. It is quite cheaply produced by first impregnating the cloth to be dyed with a solution of a manganese salt (manganese chloride is the cheapest), and then, by means of a second bath of alkali, forming a deposit on the fibre of pink manganese hydroxide—corresponding to the greenish ferrous hydroxide—which, on exposure to the air, absorbs oxygen and forms the final brown color.
Unfortunately the alkali used in this case must be caustic alkali—potassium hydroxide orsodium hydroxide—and not one of the mild alkalies like the carbonates or bicarbonates, which will do for the iron color. And, therefore, although it is rather more expensive, and is somewhat liable to weaken the fabric, it is generally more convenient to obtain this color by a one-bath process. A purple solution of the salt known aspermanganate of potash, is prepared and the cloth dipped. After being immersed it is wrung carefully and shaken out, and the red or purplish color gradually changes into the final brown. As soon as this change has taken place the goods should be plunged into a hot soap bath and thoroughly scoured, both to remove any loosely adhering particles of color which cause rubbing, and to prevent tendering of the cloth.
The latter danger, however, is always present with this process and, therefore, full shades should not be dyed excepting on heavy, strong goods like rugs or very coarse yarns or cloth. Even then it should be done carefully and by successive dippings, with a careful washing, after the color has been developed in the air, between each bath.
This injury to the cloth which, hitherto, has been the great drawback to the permanganate process, can be avoided by dipping the goods, as soon as possible after leaving the dye-baths, into a solution containing glucose, as, for instance, two or three spoonfuls of Karo (corn syrup) or molasses in each gallon of hot water. Directly the purple-stained cloth touches this solution the color changes to brown, without affecting the strength of the materials.
This color, like the other mineral colors, is rarely, if ever, to be used on silk, being altogether too likely to injure the texture and the lustre of the material.
In at least one instance, however, it has been used on animal fibres with considerable success. During the critical part of the Boer war, it was at one time necessary for England to put as many of her troops as possible—especially her mounted troops—into the field. Among others the Scots Greys, distinguished at Waterloo and made famous in many other bloody campaigns as a fine old fighting regiment, were ordered to the front. There is a tradition, dating back over two hundred years, that the horses of this regiment must all be either white or grey in color. Some heaven-sent genius at the Horse Guards—the English War Department—hinted quite forcibly to the authorities that to send out a cavalry regiment on white horses to face the Boer sharpshooters, was rather a dangerous experiment. The authorities, therefore, consulted a well-known dyeing chemist. He advised them to send down, on the troopship, some kegs of permanganate; and to instruct the officers and men to sponge each horse with a weak solution of the salt, every day at “Stables.” This was done, and, in consequence, long before reaching Cape Town, the skin and hair of every horse was thoroughly colored a soft, quiet shade of brown.
The color produced by permanganate varies, according to the strength of the solution, or rather with the number of dips in comparatively weak solutions, from a light brownish tan to a full, rich, soft, seal brown. Pleasant shades, too, can be obtained by dyeing first with the iron rust dye and then covering with the permanganate. This color is discharged, not only from textiles but from the hands, by soaking in a solution ofsodium hydrosulphite (commonly used in dyeing indigo) and then washing.
PRACTICAL DYEING
Before proceeding to the practical dyeing instruction it is well to say a few words about the equipment needed for the work.
Fortunately no elaborate or expensive outfit is necessary, even for the beginner. And after one has had a little experience, it is astonishing what an amount of interesting, and even important work can be turned out with a few of the very simplest utensils. The essentials may be set down as follows: