384 



BLEACHING 



dors such as those just described cannot bo used. Largo wheels of cast-iron are 

 employed, consisting of two concentric cylinders, between which is a closed spaco 

 heated by steam. The cloth is by this means heated on one side only, not passing 

 from cylinder to cylinder, in which case the side next to the heating surface would be 

 changed every time. The larger the cylinder or wheel, the more rapid is the drying, 



as there is more surface of cloth exposed to it at a time ; it can, for the same reason, 

 be turned more rapidly round. Well-finished goods will not rise when heated, except 

 on the pattern. Messrs. Bridson have a large business in jacconets for artificial 

 flowers on account of this peculiar finish. They are formed of a plain cotton cloth, 

 but stand the pressure of hot irons without curling. 



No essential difference is made in bleaching muslins, except that sometimes weaker 

 solutions are employed for very tender goods. Mr. Barlow makes no difference as a 

 rule in the strength given in describing his process ; with very strong goods, he some- 

 times uses the liquids stronger. 



It is desired occasionally to bleach goods which have coloured threads woven into 

 them, or colours printed on them. In these cases great caution must be used. It 

 is needful to use weak solutions, but more especially not to allow any one process to 

 be continued very long, but rather to repeat it often than to lengthen it. This may 

 be stated as a general rule in the bleaching of goods. It would indeed be possible to 

 do the whole bleaching in one operation, but the cloth would be rotten. This arises 

 from the fact that, at a certain strength, bleaching -liquor or soda is able to destroy 

 the fibre ; but another and less strength does not act on the fibre, but only on such 

 substances as colouring-matters. This care is needed when printed goods which have 

 a white ground are treated. The white ground takes up colour enough to destroy its 

 brilliancy, and soaping does not always remove it. The bleaching then is effected by 

 using bleaching-liquor at A Twaddle. Some persons put a Turkey-red thread into 

 the ends of the pieces. The original use of this seems to be scarcely known among 

 the manufacturers. It was used as a test of the mode of bleaching employed. If 

 strong solutions be used, which are apt to spoil the cloth, the colour of the dyed 

 threads will be discharged. When the separate system is employed, this is evaded 

 easily ; it is the practice to keep the ends containing the red threads out of the liquid, 

 allowing them to rest on the side of the vessel. 



Sometimes chlorate of potash is used for the same purpose, souring as with the 

 bleaching-powder. The colours may, in this manner, bo made much more brilliant 

 than before, although a little excess will discharge them. A good deal of the effect 

 may be owing to the better white given to the ground. Besides these processes for 

 bleaching, another was at one time introduced, which consisted of immersing the cloth 

 in a solution of caustic alkali, and afterwards steaming in a close vessel. It is not 

 now in use. Alkali of 1020' specific gravity was used. 



The new or continuous Process. This method owes its introduction to David 

 Bentley, of Pendleton, who patented it in 1828. It consists in drawing the goods in 

 one continuous line through every solution with which it is desired to saturate them. 

 This is done by connecting the ends of all the pieces. The motion of rollers draws 

 the chain of cloth thus formed in any desired direction, and through any number of 

 solutions any given number of times. We shall allow him to use has own words. 



