4. First soda boil: 120 lb. caustic soda (solid), boil 12 hours, wash.
5. Chemick : bleaching powder solution 1° Tw., steep 2 to 4 hours, wash.
6. Second soda boil or " white boil " : 120 lb. soda ash, boil 12 hours, wash.
7. White sour : sulphuric acid 2° Tw., steep 2 to 4 hours, wash.
8. Blue, squeeze, and dry.
Scotch Process.
1. Wash.
2. Lime boil : 600 lb. lime, boil 10 hours, wash.
3. Lime sour : hydrochloric acid 2° Tw., steep 4 hours, wash.
4. Ley boil: 500 lb. soda ash, 40 lb. soft soap, boil 10 hours, wash.
5. Chemick : bleaching powder solution 1° Tw., steep 4 to 10 hours, wash.
6. White sour : sulphuric acid 2° Tw., steep 2 hours.
7. Wash, blue, squeeze, and dry.
This last process is for goods which weigh about 8 to 9 lb. per 70 yds.; when the cloth is heavier two ley boils are given, washieg between. For muslins weighing about 5 lb. per 70 yds., 400 lb. lime and 400 lb. soda ash are used instead of the quantities given.
Sometimes it hsppens that the goods contain coloured threads, either at the piece ends, " headings," along the borders, or even throughout the piece, and which must be preserved. In such cases, alight modifications are made in the process ; these can only be learnt by experience. If indigo blue or madder-lilac threads are present, the lime boil is omitted, and soda ash is used instead. If chrome-orange threads are present, the souring must be omitted. Green ornaments containing prussian blue require very careful treatment, and to be gently boiled for a short time with weak solutions of soft soap alone, followed by washing and chemicking.
For very light fabrics, such as book muslins, lappets, harness and Nottingham lace cmisins, &c., the so-called continuous process or chain bleaching is not used, owing to the delicate texture of the materials. In the. finest muslins, too, the warp threads are in psirs, owing to two threads having bean passed through one division of the iced in weaving, and the grey muslin has conse quently a somewhat stripy appearance. The chain bleaching process would not so readily separate the double threads of the warp, since the pieces, during the washing, &c., are always in a state of tension. Probably, however, the slack washing machines, to which reference will be made in speaking of linen bleaching, may be worth trying for fine muslin bleaching; in this case, the more rapid chain bleaehing would, of course, he employed throughout.
Each piece of the above-mentioned fine materials is made up iuto a loose bundle and thrown into the kier (generally low-press), along with lime water or soda ash solution, as the case may be, for the boilings. The washing is performed in " dash-wheels." Fig. 356 represents one of
these. It consists of a stoutly-made hollow wooden drum A, divided into four compartments, each quadrant provided with a hole B for putting in and taking out the pieces. Jets of water are admitted through openings C on both sides, and the dirty water runs off by small holes D in the periphery. E is the water main to supply the pipe F, which conducts the water through the openings C. The machine is so constructed that the water is turned on or off by the same leverage which throws the wheel into or out of gear. One or two bundles of cloth are put into each com partment, and, as the wheel revolves, are tossed from side to side. The dash-wheel is about 6 to 7 ft. in diameter, and about 30 in. wide. The speed should not be too slow, or the pieces will slide down the sides of the compartments ; but if too quick, the centrifugal force will hold them stationary. This washing is one of the very best, and is very gentle ; it has only been super seded by those described, wherever possible, on account of its slow and intermittent character. For ehemicking and souring, the stone tanks with false bottoms and drainers, as described above, are employed.
Instead of the squeezers, the "hydro-extractor " is used. Fig. 357 represents the best description, as constructed by Messrs. Duncan Stewart and Co., Glasgow. It c.onsists of a drum or cage made of close galvanized wirework, or of perforated copper sheeting, so supported by a spindle below that the whole can be made to spin like a top, but will stand upright when at rest. It is driven by friction from below, and can be made to revolve at the rate of about 1500 revolutions per minute, with a perfectly regular and smooth movement. The whole is proteded by a strong cast-iron case. The wet bundles of goods are placed in the cage, as evenly and equally as possible, so as to balance it; when it is made to revolve, the water is expressed by the powerful centrifugal force through the perforations and into the outer case D, whence it escapes by the pipe P. When taken out after a few minutes, the goods have lost all excess of water, and the treatment is so gentle, that the most delicate fabric is not injured.