Page:Encyclopædia Britannica, Ninth Edition, v. 3.djvu/838

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820
BLEACHING

pasteboard, in a Bramah press, and after a certain interval an iron plate is substituted for the pasteboard, to prevent any inequality in the pile. Finally, the folded pieces are prepared for the market by fastening a band of gilt and ornamented paper around each end, which with the imprinted device is in some way regarded as a guarantee

of good quality.

The whole operations of bleaching and finishing occupy on an average eight days, although goods can be hurried through much quicker if occasion arises. The cost, which of course will vary with the price of fuel and other circum stances, is very small as compared with the value of the material, and does not on an average, for shirting calicoes and the like, exceed lid. per fb weight of cloth.


Bleaching of Thread.


We have been favoured by Messrs J. and P. Coats of Paisley with the following outline of the processes in the bleaching of thread:—

1. The various Nos. of thread are prepared before boiling.

2. The first boil. The kier used is a common vomiter, into which are put water and a solution of caustic lye, the proportions being regulated by the number of pounds of thread to be treated.

3. The first bleach. The thread is placed in a box, and a sieve let down upon it. Underneath the box is a well which is filled with water and chlorine. The liquor is drawn up by a pump, and thrown upon the sieve, through which it passes, and filters through the thread into the well.

4. The thread is next moved into a souring-box, also covered with a sieve, where it is washed to take out the chlorine of the pre vious process.

5. A souring- well under the souring-box is now filled with water and sulphuric acid, and this mixture, called the sour, is pumped up on the sieve over the souring-box, through which it runs back into the souring-well, in the same manner as described in process No 3.

0. Before removing the thread from the souring-box it is washed with water through the sieve.

7. It is next washed in a washing-machine.

8. The scald, or second boil in kier. Various mixtures are used for it. Some prefer black soap and crystals of soda ; others use caustic lye.

9-13. Repetition of Nos. 3, 4, 5, 6, and 7.

14. The thread is now extracted, i.e., dried in hydro-extractors.

15. Stocking. The stocks are boxes about 3 ft. long, by 2 ft. wide, and 2 ft. deep, with a large wooden mallet hung in each, similar to those used in bleaching linen. The thread hanks having been properly prepared, so that they will not get loose, are put into the stocks with a mixture of hot soap and water, and beat there till of the proper colour. It is then taken out, and

16. Washed in washing-machine, and

17. Extracted.

18. The blueing process is done in a box filled with a solution of water and extract of indigo. As much thread is put in as the box will contain. It is let stand for a time, after which it is taken out and thrown on a barrow.

19. It is next taken to extractor and dried, and

20. Placed in the stove. After being a sufficient time there it is

21. Removed to cooling shed, where it is hung up to cool.

22. It is now taken to stretching-machine, where it is passed over hot rollers to take out the curl and moisture received in cool ing shed.

23. Taken to warehouse, where Nos. are classed and made up in bundles.


Bleaching of Linen.


The bleaching of linen is a much more tedious and difficult operation than the bleaching of cotton. The process of water-retting, or rotting, by which the fibre is separated from the woody portion of the stalk, lodges a large proportion of colouring matter in the fibre, with which it enters into very intimate combination. The amount of colouring matter which has thus to be dealt with in the bleaching of linen is very great, being as much as one-third of the entire weight of the fibre. In the early part of the century a great amount of public attention was given to a plan proposed by Mr James Lee for preparing flax fibre without the process of steeping or retting, by which it was affirmed that, among other advantages, it would only be necessary simply to wash, in soap, linen fabrics made from fibre so prepared, to render them pure and white. Mr Lee obtained a special Act of parliament allowing the specification of his patent to remain sealed for seven years, and his plans were entered into in a most full and laborious manner by the Irish Linen Board. After the expenditure of many thousands of pounds on his machines and experi ments, the plan had to be entirely abandoned as a failure. More recently, Chevalier Claussen renewed the attempt to prepare flax without steeping, by breaking it by means of machinery, separating the refuse part of the stalk from it, and then by a chemical process splitting the hollow fibres, so as to reduce them to a soft cottony state fit for spinning by means of the cotton-spinning machinery. The fibre was proposed to be split by steeping the prepared flax in a solution of carbonate of soda, and then plunging it into dilute sulphuric acid. The sudden evolution of carbonic acid gas within the hollow tube of the flax was said to have the effect of splitting up the fibre and reducing it to fine flat threads possessing the felting properties of cotton. Sir Robert Kane, in his Report to the House of Com mons, May 20, 1852, states that the whole process failed. The machinery for the beating and cleansing of the flax failed to separate it sufficiently from the refuse part of the stalk ; and the chemical process for the splitting of the hollow tube only broke up small portions of the exposed ends, leaving the greater portion untouched. Various other plans of preparing flax fibres without water or dew- retting have from time to time been proposed and patented, but hitherto none of them has stood the test of extended practical operation. Till towards the end of last century the bleaching of linen both in the north of Ireland and Scotland was accomplished by bowking in cow s dung and souring with sour milk. In the year 1764 Dr James Ferguson of Belfast received a premium of 300 from the Irish Linen Board for the application of lime in the bleaching of linen. Notwithstanding this reward the use of lime in the bleaching of linen was for a long time after wards forbidden in Ireland under statutory penalties, and so late as 1815 " Mr James Barklie, a respectable linen-bleacher of Linen Vale, near Keady, was prosecuted for using lime in the whitening of linens in his bleach- yard." The bleaching of linen to the present day is conducted much more in the primitive fashion of last cen tury than is the practice with cotton-bleaching. Owing to the stiffness and inelasticity of flax fibres, a great part of the machinery used for cotton is not available for linen, and solutions of acid and bleaching-powder require to be used in a very dilute condition for linen fabrics, involving frequent repetitions of the various processes before a satisfactory white is produced. " Crofting," or exposure to the air on grass, is also very largely resorted to in the bleaching of linens, especially for plain shirting and sheeting, which necessitates the possession of very extensive grass parks in connection with works, and renders the pro cess both tedious and subject to the influences of the weather. A large proportion of linen cloth is half-bleached or improved in the yarn before being woven, and it con sequently requires less bleaching than that which comes in its original " green " condition. The following is an outline of the two chief methods, with and without crofting, as pursued in the principal Scotch linen bleachfields at the present day:—

I. WITHOUT CROFTING. 1. Limed. 2. Boiled in open kier for about 6 hours. 3. Washed at washing-mill or stocks, 4. Soured with hydrochloric acid, and piled in sour for some hours. 5. Washed at stocks. 6. Boiled in soda-ash for 8 or 1 10. Boiled in alkali for G or 7 10 hours. hours. 7. Again boiled. 8. Liquored in chlorine solution and piled up. 9. Washed. 11. Liquored in chlorine solution. 12. Washed. 13. Soured with sulphuric acid.

14. Washed.