_Preparation of the dye vat._ The vessel used should be deep and upright so that an unnecessarily large surface is not exposed to the air, and a sufficient space for dyeing is obtained above the sediment. A galvanised dust bin, or a barrel (provided it is not of oak or any other wood which contains tannin), make good indigo vats. Put 16 gallons of water in the vat at a temperature of 65-70 deg.F. In order to counteract the effects of the atmospheric oxygen contained in the water of the vat, additions of zinc dust and lime are made some hours before the stock solution is added. A pinch of zinc dust and an ounce of lime, previously slaked, should be added and the vat stirred. Stirring must always be done gently and smoothly, every effort being made not to take air into the vat. At the same time it must be stirred up from the bottom so that the sediment is mixed with the liquor above it. The best tool for this purpose is a broom stick, to one end of which a piece of wood is nailed, like a garden rake. When all is ready, carry the stock solution to the dye vat, and, to avoid splashing through the air, hold it in the water of the vat while gently pouring out half its contents. Stir up the vat and cover it until it shows a clear yellow colour under the surface of the scum. This may not happen for 24 hours. A good way to test the colour of the vat is to push back the scum with the edge of a saucer or plate, then dip it halfway into the liquor. Against its white surface the colour of the liquor will be plainly seen. It should look like good light ale. If the liquor is greenish and sufficient time has elapsed, another pinch of zinc dust and a little more lime must be added as before, and the vat again stirred, allowed to settle and again tested. A little difficulty may be found in getting the vat to start, but once it has worked well no difficulty will be found in starting it again. It will work more easily as it gets older. As indigo does not penetrate easily, every effort must be made to help it to do so. The stuff to be dyed must be thoroughly scoured so that no particle of grease, size, or any other impurity is present. Every effort must be made to prevent unreduced indigo from attaching itself to the cotton. Never begin to dye in a vat which is greenish. The unreduced indigo will attach itself to the stuff and be wasted. Your time will also be wasted in washing it off. The vat should be thoroughly stirred and allowed to settle each day before dyeing begins. When the sediment has settled, the froth should be carefully skimmed and kept to return to the vat when the day's dyeing is finished.