As soon as the indigo is dissolved and properly diluted, damp the fire and cover over the solution; after it is settled put in a pattern, which, when taken out, will turn blue on being exposed to the air; if it does not, more clear lixivium must be added. Of this solution of indigo such proportions are to be added to the woad vat as are directed in the preceding process. _Rules to judge of the state of the woad vat._ The vat is ready for working, and to dye blue, when the sediment at the bottom, on being taken out of the vat changes to a fine brown-green. When the froth which rises in great bubbles on the surface is of a fine Prussian-blue, and when the pattern which has been steeped an hour, comes out of a dark grass-green, and changes in the air to a blue; when the liquor is clear and reddish, and the drops which stick to the rake are brown; when the sediment changes colour on being taken out of the liquor, and becomes brown on exposure to the open air: when the liquor is neither harsh nor greasy to the feel, and neither smells of lime nor of ley, the vat is known to be in a proper state for working. _Indications when a vat has had too much or too little lime._ These extremes ought to be carefully avoided. When the lime is deficient, or a pattern comes out of a dirty grey, and the sediment does not change its colour, there is scarcely any effervescence on the vat; the liquor smells only of lime, or of the lixivium of lime. _To remedy the deficiency of lime._ If the vat be not too far gone, after the addition of a little bran, madder, and some woad, then try the patterns from hour to hour; thus you will be enabled to judge. A _deficiency_ of lime is evident when there is no effervescence on the liquor; and when, by dashing about the surface of the liquor, it makes a hissing noise, and by the bursting of a number of small air bubbles, which as soon as they are formed break, and appear tarnished, and are not large, nor of a fine colour; the liquor too has an offensive smell, like rotten eggs; it is harsh and dry to the feel, and the sediment, as has been before observed, does not change colour when taken out of the liquor. Sometimes such a condition of the vat is absolutely irremediable; but when not gone too far, sprinkle some lime into the liquor, and stir it. If you can thus remedy the defect, and bring the liquor to smell of lime, and to feel soft, cover the vat, and let it stand. If, at the expiration of an hour and a half, the effervescence begin, you may put in a pattern; in an hour afterwards, it may be taken out, and regulate your process by the degree of green which the pattern has imbibed; but, in general, when vats are thus out of order, they are not so soon recovered. _To work a vat which is in proper order._