[207] Herod., i, 195.
[208] Athen., ix, 77.
[209] ‘Hist. Nat.,’ xxv, 57, &c.
[210] {Transcriber’s note: Footnote omitted by publisher.}
Bleaching continued to be practised with no essential change of its principles until the discovery of chlorine, to which we shall presently refer. In the last century Holland obtained the best name for bleaching. The process passed then to Ireland and Scotland, and thence into England. It was even customary to send goods from this country to be bleached in Holland. The first attempt to vie with Holland was made, in Scotland, in 1749.
The first steps towards the modern or chemical system of bleaching were the investigations of Berthollet on chlorine, in 1784, but which were not communicated to the French Academy until the year 1787. The knowledge of the use of chlorine as a bleacher was soon afterwards brought to this country by the Duke of Gordon, and by Prof. Copeland of Aberdeen, and through them was practically applied by Messrs Milnes of that place. About the same time James Watt, a correspondent of Berthollet, successfully introduced its use in the neighbourhood of Glasgow, and then generously laid a statement of the results before the Manchester manufacturers. In enforcing the importance of the new substance and process on these gentlemen, he was ably followed and seconded by Dr Henry. In 1798, Mr Charles Tennant, of Glasgow, obtained a patent for a new bleaching liquor prepared by saturating lime water with chlorine; and another, in 1799, for dry chloride of lime, a substance which is still preferred as a bleacher to all other preparations of chlorine. The new or continuous process of bleaching, as it is called, and that which is at present in general use in all the chief bleach-works of Lancashire, was introduced by Mr David
Bentley, of Pendleton, and patented by him in 1828.
Proc. Bleaching is commonly said to be natural when exposure to light, air, and moisture forms the leading part of the process; and to be chemical when chlorine, chloride of lime, sulphurous acid, or other like substances are employed. In some cases, as with linen, the two processes are combined. The subject requires to be noticed under separate heads, depending on the material operated on:—
I. Bleaching of Cotton:—Cotton is more easily bleached, and appears to suffer less from the process than most other textile substances. On the old plan it was first (1) thoroughly washed in warm water, to remove the weaver’s paste or dressing; then (2) ‘bucked’ or ‘bowked’ (boiled) in a weak alkaline lye, or in milk of lime, to remove colouring, fatty, and resinous matters, insoluble in simple water; and after being (3) again well washed, was (4) spread out upon the grass, or bleaching ground, and freely exposed to the joint action of light, air, and moisture (technically called ‘crofting’). The operation of ‘bucking’ in an alkaline lye, washing, and exposure was repeated as often as necessary, when the goods were (5) ‘soured’ or immersed in water acidulated with sulphuric acid, after which they (6) received a final thorough washing in clean water, and were (7) dried, finished, and folded for the market. From the length of the exposure upon the bleaching ground this method is apt to injure the texture of the cloth; and from the number of operations required is necessarily expensive and tedious. It is therefore now very generally superseded by the system of chemical bleaching briefly described below.
In the CHEMICAL SYSTEM of bleaching the goods are ‘washed’ and ‘bucked’ as on the old plan, then submitted to the action of a weak solution of chloride of lime, and afterwards passed through water soured with hydrochloric or sulphuric acid, when they have only to be thoroughly washed, and to be dried and finished, for the entire completion of the process.