the bleaching of linen are, except
in one or two unimportant particulars, the same as were used in the
middle of the 19th century. In principle they resemble those used in
cotton bleaching, but require to be frequently repeated, while an
additional operation, which is a relic of the old-fashioned process,
viz. that of "grassing" or "crofting," is still essential for the
production of the finest whites. Considerably more care has to be
exercised in linen bleaching than is the case with cotton, and the
process consequently necessitates a greater amount of manual labour. The
practical result of this is that whereas cotton pieces can be bleached
and finished in less than a week, linen pieces require at least six
weeks. Many attempts have naturally been made to shorten and cheapen the
process, but without success. The use of stronger reagents and more
drastic treatment, which would at first suggest itself, incurs the risk
of injury to the fibre, not so much in respect to actual tendering as to
the destruction of its characteristic gloss, while if too drastic a
treatment is employed at the beginning the colouring matter is liable to
become set in the fibre, and it is then almost impossible to remove it.
Among the many modern improvements which have been suggested, mention
may be made of the use of hypochlorite of soda in place of bleaching
powder, the use of oil in the first treatment in alkali (Cross &
Parkes), while de Keukelaere suggests the use of sodium sulphide for
this purpose. With the object of dispensing with the operation of
grassing, which besides necessitating much manual labour is subject to
the influences of the atmospheric conditions, Siemens & Halske of Berlin
have suggested exposure of the goods in a chamber to the action of
electrolytically prepared ozone. Jardin seeks to achieve the same object
by steeping the linen in dilute nitric acid.

Since the qualities of linen which are submitted to the bleacher vary
considerably, and the mode of treatment has to be varied accordingly, it
is not possible to give more than a bare outline of linen bleaching.

Linen is bleached in the yarn and in the piece. Whenever one of the
operations is repeated, the strength of the reagent is successively
diminished. In yarn-bleaching the sequence of the operations is about
as follows:--(1) Boil in kier with soda ash. (2) Reel in bleaching
powder. This operation, which is peculiar to linen bleaching, consists
in sus