Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 1, 1802).djvu/311

Rh disengaged by the milling. Soft soap is preferred to hard, for this purpose, as the latter contains a considerable quantity of sea-salt, which is prejudicial to the cloth.

The management of coarse cloth in this operation is very different from that of fine; for the former, instead of being worked by the hands (a method which would be too expensive), is laid upon a table, rubbed over with soap, and then placed between what are called rubbing-boards, which have ridges and grooves from one side to the other, in the form of teeth.

The starching and blueing, which is the last operation, differs so little from the process employed by laundry-women, that it scarcely requires description. But it often happens, that the cloth, when exposed to dry in the open air, after being starched, is wetted by rain, which frustrates the effects intended by the operation: to remedy this inconvenience, many bleachers employ a dry-house, where the linen may be dried in all weathers.

As bleaching is a process connected with manufactures, and cannot be performed with advantage by private families, it is useless to enter into farther particulars. But the art is still susceptible of improvement; for scarcely a year elapses, which does not produce some new discovery in this useful branch of manufactures. We shall, therefore, content ourselves with communicating a few of such hints as may prove advantageous to the practical bleacher; and with which, we presume, there are many persons still unacquainted.

The new method of bleaching with the dephlogisticated or oxygenated muriatic acid, or spirit of salt combined with manganese, is founded upon the remarkable property which that acid possesses of destroying vegetable colours; and, though various attempts have been made to introduce it into this country, the difficulties or disadvantages attending it have prevented its general adoption. This acid was first applied to the purpose of bleaching, by M. ; and the particulars of the process are described at length in a treatise on bleaching, published a few years since at Edinburgh; and likewise in the Supplement to the Encyclopædia Britannica.

It is to be regretted, that no exact comparative statement of the difference of expence between the old and new methods of bleaching, has yet been laid before the public; but it is probable that the acid drawn from one pound of salt, will whiten four of linen cloth, without any addition. The expence in this case may appear trifling, but when we compute the vitriolic acid which is employed, and that the residuum is almost useless, it will soon be found to be very considerable; and upon the whole, the advantage may be only in the saving of time: but M. asserts, that by this method the texture of the cloth is less injured than by that hitherto practised.

The oxy-muriatic acid is also very generally used for bleaching paper. According to M., blotting-paper, when put into it, is bleached without suffering any injury; and old books, and prints, when soiled in such a manner as to be scarcely distinguishable, have been completely restored to their original state. The simple immersion of a print in this acid, is sufficient to produce that desirable effect; but with books, some ther