good quality, free from stones, badly burnt pieces or any other insoluble material, so that when slaked it should give a fine smooth pasty mass.
Lime should not be slaked too long before using, as it absorbs carbonic acid from the atmosphere, whereby carbonate of lime is formed, and this is useless for liming cloth. The pasty slaked lime may be mixed with water to form the milk of lime, and this can be run from the cistern in which it is prepared into the liming machine as it is required; the supply pipe should be run into the bottom of the trough of the liming machine and not over the top, in which latter case it may splash on to the cloths and lead to overliming, which is not to be desired on account of its liability to rot the cloth. The amount of lime used varies in different bleachworks, and there is no rule on the subject; about 5 lb. to 7 lb. of dry lime to 100 lb. of cloth may be taken as a fair quantity to use.
The lime boil has for its object the removal or rather the saponification of the resinous and fatty matters present in the grey cloth, either naturally or which have been added in the process of weaving, or have got upon the cloth accidentally during the processes of spinning and weaving. With these bodies the lime forms insoluble lime soaps; these remain in the cloth, but in a form easily decomposable and removable by treatment with acids and washing. Soda or potash is not nearly so good for this first boiling as lime—for what reason is somewhat uncertain, but probably because they form with the grease in the cloths soluble soaps, which might float about the kier and accumulate in places where they are not required and thus lead to stains, whereas the insoluble lime soap remains where it was formed. The lime also seems to attack the natural colouring matter of the cotton, and although the colour of the limed cloth is darker than before boiling, yet the nature of the colour is so altered that it is more easily removed in the after processes. Besides
these changes the starchy matters put into the cloth in the sizing are dissolved away. Great care should be taken to see that the goods are evenly laid in the kiers, not too tight, or the liquor will not penetrate properly; and not too slack, or they will float about and get entangled and more or less damaged. Then again care should be taken, especially when using low-pressure kiers, to see that the supply of liquor does not get too low, in which case the goods in the upper part of the kier are liable to get dry and are tendered thereby. So long as the goods in the kiers are not allowed to get dry there is no risk of damage; this trouble rarely arises with the Barlow and injector kiers. The inside of the kiers should be kept well limed, so that the goods shall not come in contact with the bare iron or metal of which the kier is constructed, as this would be very likely to lead to stains being produced which are by no means easy to remove. It is usual, and it is a good plan with almost all kinds of kiers, except the Mather and Edmeston kiers, to put a number of large pebbles or small stones at the bottom of the kier, which serves to make a false bottom on which the goods rest and through which the liquor penetrates and flows away. Before using, the stones should be well washed to free them from dirt and grit.
The lime boil is carried out in what are called "kiers". Many forms of kiers have been devised, but the one in most general use is that known as the "injector kier," of which a drawing is given in Fig. 4, of the form made by Messrs. Mather & Platt of Salford. Injector kiers are made to work either under a pressure of 40 lb. to 50 lb. of steam per square inch, when they are called high-pressure kiers, or at a pressure of 15 lb. to 20 lb., when they are called low-pressure kiers. The one shown in the drawing is intended for low-pressure kiers. The principle of construction is the same in all, the details varying somewhat with different makers. Injector
Fig. 4.—Mather & Platt's Low-pressure Bleaching Kier.
kiers consist of a hollow, upright iron cylinder made of plates riveted together; the top is made to lift off, but can be fastened down tightly by means of bolts and nuts as shown in the drawing. From the bottom, and placed centrally, rises a pipe, known as the puffer pipe; this terminates at the
top in a rose arrangement. The lower end of the pipe is perforated. A jet of steam is sent in at the bottom of this pipe, and by its force any liquor at the bottom of the kier is forced up the puffer pipe and distributed in a spray over any goods which may be in the kier. The liquor ultimately finds its way to the bottom of the kier ready to be blown up again. This circulation of the liquor can be maintained for any length of time and through its agency every part of the goods gets thorough and effectual treatment.