The well-wetted materials are placed in the reduced dye-bath, and stirred and worked for five or ten minutes, or longer, according to the depth of shade experienced. For full shades, however, as in the case of indigo, it is much better to build up the color by successive dippings than to try to put it all on in one bath. For heavy goods the addition of a little Turkey red oil, about half a tablespoonful to the gallon, is an advantage, though not absolutely necessary. When thoroughly impregnated with the dye-liquor, the goods are taken out, wrung carefully, two or three times, to remove the waste liquor as evenly as possible, and then shaken out and exposed to the air for fifteen or twenty minutes. They are then boiled in a soap bath for about twenty minutes, and then well rinsed, and dried. This hot soap bath, as before mentioned, is of great importance in most of these colors, not only for getting rid of loosely fixed dyestuff, but for oxidizing and fixing the color itself. For dark shades it is well, as in the case of the Sulphur colors, to add salt—three or four tablespoonfuls per gallon of dye-liquor—to the bath, taking care to have it well dissolved before the goods are entered. This is always done when dyeing with Helindone Yellow 3GN, _Metz_. The shades of these new Vat colors are extremely bright and clear, and, by combining these properly, any desired effects may be produced. The splendid series of reds and scarlets for the first time allow the characteristic shades of Turkey red to be obtained, in one bath, and of at least equal, if not of superior fastness to the original. One peculiarity of these colors is their extreme fastness, not only to light and washing, acids and alkalies, but also to various oxidizing agents, such as chloride of lime or bleaching powder. Accordingly goods properly dyed and finished with these dyestuffs can be entrusted with safety, so far as the color goes, to agencies which would speedily ruin fabrics dyed in any other manner. CHAPTER VII THE BASIC COLORS In an earlier chapter it was mentioned that the modern dyestuffs originated with the discovery by Perkin, in 1856, of the violet coloring matter known as Mauveine. This dye was made by the oxidation of the then rare chemical, aniline. Following this discovery, other chemists, especially in France and Germany, soon obtained from the same chemical or from substances very closely resembling it, a considerable quantity of powerful and brilliant dyestuffs of the same general character.