| 
| ated and the fibre becomes swollen. 
| steeping water. 
I. AAR 
trot 
with a hot alkaline lye. The process of exposing 
and bucking 1 is repeated two or three times until 
the fibre is white. 
Cleansing—the third process—is effected by 
laying the goods in lukewarm water acidulated 
with sulphuric acid, and finally washing them 
thoroughly at the dash-wheel. Cotton ieee about 
5 per cent. of its weight in bleaching. 
It is remarkable that we cannot yet explain 
the manner in which bleaching is performed, 
whatever process is pursued. In the present 
case, it is probable that air and moisture (arising 
from rain, dew, or artificial sprinkling), influen- 
ced by solar light, oxidize the colour on the fibre, 
even without the assistance of alkali. But by 
exposure, the colour becomes more soluble in al- 
kali, and hence each successive bucking removes 
the portion decomposed. The final sowring re- 
moves any earthy matters which may have be- 
come attached to the fibre during the process, 
and neutralizes the last portions of alkali, which 
would have been difficult to remove by water 
alone. By the preparatory fermentation, the 
weaver’s paste, containing starch and gluten, un- 
dergoes successively the saccharine, vinous, and 
acetous fermentation, by which gluten and sine 
substances are dissolved in the acetic acid gener- 
Care must 
be taken to stop the operation before the putre- 
factive process commences, which would injure 
the fibre. 
The above operations are sometimes slightly 
varied. To hasten and complete the fermenta- 
tion, bran or rye-flour may be added to the 
The addition of alkali or lime 
(which is sometimes used) lengthens the fermen- 
tation, and should only be used where it is too 
rapid. If the goods be greasy, fermentation, 
being injurious, is omitted, and they are then 
merely boiled some hours in water, and washed. 
A bath of milk of lime is sometimes given imme- 
diately after fermentation and before bucking, 
which materially assists the bleaching, but it 
acts injuriously, unless all the weaver’s paste has 
been destroyed by fermentation and washing. 
At the present time nearly all the cotton of com- 
merce is bleached by chlorine, the atmospheric 
agents being employed as very subordinate assist- 
ants. 
Linen. —¥lax, when not retted, contains but 
little colouring matter, which can be removed by 
a few washings with soap and alkali, but the pu- 
trefactive process of retting produces a colour 
which requires a tedious series of operations to 
remove. ‘Io employ the chlorine process alone 
would undoubtedly shorten the time of bleaching, 
but the colour adheres so pertinaciously to the 
fibre, and so obstinately resists decomposition, 
that the strength of the fibre would be impaired. 
Hence a tedious atmospheric bleaching is always 
resorted to for linen, combined to a limited ex- 
tent with chlorine. Hven with this process, the 
long exposure to light, air, and moisture, the oft 
BLEACHING. 
443 
repeated operations necessarily weaken the fibre, 
as may be inferred from the loss by bleaching, 
which may often amount to one-third or 30 per 
cent. of the weight. 
The process without chlorine, as practised in 
Silesia and Bohemia, consists of, lst, steeping, ex- 
posure to light, &c., and washing; 2d, bucking, 
exposure, and sewing. 
After fermentation and washing, the linen is 
steeped for 12 hours in a solution of potash or 
waste lye (1000 water to 1 or 14 lbs. potash) at 
the temperature of 70° to 80°, ne out, and, 
without being washed, caren out upon grass 
to the action of the air until dry, and for several 
hours after. It is again steeped and exposed to 
the air, the temperature of the solution being 
gradually raised at the last steeping, but not 
above 170°. ‘The steeping and exposure being 
repeated 2 to 5 times, the linen is washed in the 
dash-wheel, steeped again 1 to 3 times in alkaline 
solution, eal then properly bucked. 
The bucking solution contains at first 4 lbs. 
potash to 1000 water, and the temperature be- 
ginning with 95° is increased during 18 hours to 
boiling. The linen is then exposed to the air as 
before, while still hot, and wet with the solution 
until fully dry. This alternate bucking and ex- 
posure is repeated 8 or 10 times, the alkaline 
solutions being rendered a little stronger, but not 
exceeding 4 Ibs. to the 1000 of water ; the linen 
is then washed in the dash-wheel. It is again 
steeped and again bucked several times, the 
liquors employed being weaker, and the linen 
exposed on the grass for a longer time, and being 
kept moist by sprinkling. 
Thus, after steeping 8 to 10 times, bucking 12 
to 15 times, and as often exposing it, which ope- 
rations require 60 to 70 days, the fen is suffi- 
ciently white for domestic use. But for a pure 
white, it is next passed through a bath acidulated 
with sulphuric acid, steeped, bucked 2 to 3 times 
more, and exposed, again passed through the 
acid, and finally cleansed in the dash-wheel. The 
whole process requires 80 to 90 days, and the linen 
loses from 12 to 25 per cent. of its weight, the 
less in proportion to its fineness. 
The theory of the above process may be thus 
explained :—The stem of flax and hemp consists 
of the inner woody part, or boon, surrounded by 
the har] like a fibrous sheath, oad externally the 
cuticle. The harl is witli with the boon and 
cuticle by a cement of gluten, gum, resin, &e., 
which is destroyed by retting (putrefaction in 
water or moist air). When the retting is com- 
pleted, the harl is easily separated from the 
others, but beside its natural colour, it has re- 
ceived a deposit of a humus-like substance, of a 
more or less dark colour, which is insoluble 
in boiling water, in acids, and alkalies. But 
when it has been exposed to the air, light, and 
moisture, it becomes soluble in caustic and car- 
bonated alkali. The bleaching succeeds much 
better when the fibre, imbued with alkahy, is eX- 
oe: 
