Urbana union. [volume] (Urbana, Ohio) 1862-1872, 1869-08-04
The Process of Bleaching.

TIE ancient Egyptians used an alkali,
extracted from the ashes of plants, for
bleaching cloths and other articles, and
by this process the cOlOTing matter
which the cloth contained was some
what imperfectly removed. If the ar
ticle subjected to the liquid steep was of
a deep and fixed dye, the alkali failed
to render it perfectly white. Goods of
faint tint were usually freed from all
trace of their original color. The pro-
cess, however, was unsatisfactory, both
on account of the time consumed as we'll
as the great injury done to the mateTi-
al, as the alkali cut the fibre to a great
er or less degree. For a long period q
substitute was sought in vain, but the
experiments of chemists at last led to
the introduction of other and better sub
tances. These were employed i'll bleach
ing cOttOns, linens, wOOlens, silks, straw,
leather, and other articles. Linen goods,
manufactured in Ireland and Scotland,
where, until about the commencement
of the last century, sent to Holland to
be bleached. Several months were re-
quired for this purpose, butwarm wealth
er and sunshine were essential to the
process, and cloths sent in the au-
tumn were not returned until the eX-
piratiOn of an entire year. This pTac-
tice gave the name of Hollands to this
class of linens. Bleaching is entirely a
chemical process, and it has attained its
present importance by the use of chemi-
cal discoveries; but it is yet imperfect.
Iy understood. Only constant practice
and very close observation serve tx
make the means employed meet the re
quirements, especially when fabrics arr
of delicate fibre. Pure q. c. soft watel
is much better than spring q. 2. hard
water for bleaching purposes, and il
connection with the action of the sun,
rays, will in a short time reduce the col.
or of all articles to a lightes shade.
To render articles free from grease and
gIutinOus substances, they are first i'm
mersed in alkali, and are thus rendered
more susceptible to the action of the
bleach.
The art Of extracting color, long q Sc
cret in the low counties, was the alter
nate sleeping of fabrics in alkaline liQu-
Ors of different strength, called buck
ings, followed by thorough boiling and
washing, and long exposure upon close
ly trimmed lawns or meadow lands
The articles bleached were also frequent
Iy sprinkled with water during the day;
this process is called cTOfting The cloth
in sour milk, and subsequently made
white by repeated washings and croft
ings.
One DR.. Hope employed diluted sui
phuric acid as a substitute for sour milk,
and in the course Of few hours perform
ed that which had previously required
months to accomplish. After this much
time was consumed in finishing, particu-
laTly crOfting.
In Bohemia, linens are subjected to Il
fermenting process, then boiled, STEPPED
in alkaline liquors, and crOfted upon the
grass; each of these several operations
being repeated alternately, q great num-
Der of times, during two or three months.
To render the cloth perfectly white, it
is afterward placed in a bath acidulat-
ed with sulphuric acid, immersed in ak
ali, again crOfted, and finally complete
ly cleansed by washing in a revolving
cylinder, called a dash-wheel
The discovery of chlorine gas in IVA
led to a great timprOvementin bleaching.
The gas was used in solution in water;
but its preparation was found detriment-
al to the health of the wOrkmen, and the
fibre of cloth was injured by its action
when stepped in the mixture. Chloride
of lime was first prepared in IT98, and
used in the form of a saturated liquid
solution, but the year following. dry
Of lime, or bleaching powder,
was made.
The new process varies somewhat, ac-
cOrding to the fabric under treatment
Cotton goods are first subjected to the
operation Of singeing off the loose fibers,
by passing the cloth over heated cyIin-
dcrs. Next it is soaked several hours in
water, followed by the use of the dash
wheel. Boiling in lime water is resort
ed to in order to dissolve the grease.
which is eradicIted by soft water. The
sOUring process dissOlves out the lime,
and succeeding washing prepares the
cloth for bleaching. The cloth is now
in Il dilute solution of chloride
Of lime. For every pound of cloth there
is used half a pound of chloride of lime,
dissolved in three gallons of water
washing follow, and includ- t
ing the calendering, these processes are /
repeated about twenty-five times. BY /
his mode there can beas much perform ,
,d in two or three days as formerly re- /
IUired months of care and labor to ac- /
The cost amounts to about /
.wenty cents per piece of twenty-fOUr
Yards of ordinary sheeting.
Bleaching linens by the new process
IS effected by stepping, boiling, wash
ng, securing, etc, involving about
Wenty operations, in connection with
.rOfting from thirty to sixty days.
WoOleus are secured in II warm bath
If ammoniacal lye, or caustic soda, to
rec them from the oily and waNy mat
er, and after being rinScd i'm pure soft
water, the bleaching is effected 10y
means of sulphurous acid gas. The
FOODS are suspended in q close room, and
he apartment is filled with the vapur il
If burning sulphur, which, uniting with
he oxygen of the air, forms the gas.
N from twelve to twCnty-fOur hours the
olOrs are destroyed. The cloth is then
thoroughly washed in q warm weak
,ath of soft soap, to render it soft and
,liable.
Silks are washed in n solution of soap K
Kept at the temperature of about 80 de-
Tees Fahrenheit, and afterward rinsed
'ir, placed i'm linnen bags, and boiled
or an hour or two in weaker solutions of
oap, made 10y adding to the water
wcnty pounds of soap for every hundred
pounds of silk. Various shades of white
ne given to the silk, without further
bleaching, 10y the use of very weak dives
If either litmuS or indigo. Steam is al /
10 used for bleaching silks.