A short time ago a teacher of handicraft dyeing was expatiating, in my presence, upon the impropriety of using any of the new chemical processes for dyeing, and insisted that the only way to dye indigo was to set up a vat, and feed it, and work with it as our ancestors used to. It was suggested to her that it would be at least two or three days before cloth could be dyed in such a vat. “Eight or ten days at the earliest,” was the reply. And when it was hinted that the vat would have to be frequently stirred during all that time, she proudly answered, “Stirred regularly and thoroughly every single half-hour, night and day, during the whole period.” “H—m,” remarked a bystander, “that’s a little worse than sitting up with a baby sick of the croup.” Somehow the great advantage of this particular process over the modern ones, by which a proper bath can be prepared in perhaps five minutes, failed to impress itself on some of her listeners. _Modern Chemical Vats._—As soon as it was understood just what chemical action was going on in the vats, and the object of it, chemists began to find out methods for reducing the indigo without the necessity of a long, tedious, and even nasty fermentation process. They first introduced the “copperas-lime” vat, where the reduction was done by the use of ferrous sulphate (green vitriol or copperas), and slaked lime was the alkali used to keep the indigo white dissolved. Later they introduced zinc dust, a very powerful reducing agent, in place of the copperas, avoiding in this way the large amount of precipitated iron oxide which always forms in the copperas vat, and leads to the loss of dye, and muddiness and dulness of color, necessitating a special clearing bath of dilute mineral acid. At present the most satisfactory method is to use the chemical known as _sodium hydrosulphite_, as a reducing agent, in a bath made strongly alkaline with caustic soda. Hydrosulphite is not expensive; it acts very rapidly, leaving no sediment; it causes no loss or waste of the indigo; and it does its work perfectly. Hence, with its introduction, the dyeing of indigo has become extremely simple. To still further shorten and simplify the process, the large manufacturers not only furnish indigo already ground up to a fine paste with water, but also supply it already reduced by hydrosulphite or some other reducing agent, so that it is almost ready to dye with as it is, and will dissolve almost instantaneously in an alkaline bath with the addition of just a little more reducing agent. Such products are the Indigo Vat III (_Metz_), and the Indigo Solution 20% (_Badische_). By using either of these, the preparation of a vat large enough to dye 3 or 3½ pounds of cotton is the task of but a few moments. These special preparations, however, are more expensive than the regular 20% pastes, and the hydrosulphite vat is so easy to prepare that the saving of time is hardly worth the extra cost. DYEING DIRECTIONS