BLEACHING OF RAGS 31
this has been done the roll should be eased off and the stuff brushed out
carefully.
Important fibrillation takes place in the breaker, and when strong rags are
being treated, care and skill in die breaking of them will make the beaterman's
work much easier and quicker at a later stage. The washing and breaking
of rags should on no account be hurried, as this only means bad washing and
often needless cutting up of the fibres, and consequent loss of small fibres,
besides preventing the proper defibring of the stuff in the beater, and making
the stuff work free on the machine.
Rags can never receive too much washing; the more they are washed with
clean pure water, the better.
RAG BLEACHING
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After the rags have been thoroughly washed and broken in, they are ready
to be bleached, and this operation either takes place in the breaker itself, or the
rags may be emptied into potching engines on the floor below and bleached
with a bleaching solution.
Wherever it is carried out, the bleaching consists of adding to the rag stuff
a bleaching solution of known strength, which is prepared as described in the
chapter on bleaching. The dry weight of rags in the potcher is known, and
a sufficient quantity of bleaching liquor is added, in pails, to give the required
percentage of dry bleaching powder. Supposing the strength of the solution
is 6° Twaddell, then each gallon of liquor will represent £ Ib. of dry bleaching
powder, so that if the breaker holds 100 Ib. of rags, and it requires 3 per cent
of bleach to bring them to the required colour, it will be necessary to add
6 gallons of the liquor.
No hard-and-fast rule should be made as to the number of gallons to be
put into each grade of rags, but rather a standard for colour should be adhered
to, in order to give regularity to the stock. It happens often that one boil of
rags will only require 2 per cent of bleach, while the next may require as much
as 4 per cent to give the same colour. Such wide variations as this should
not, of course, occur if the sorting and boiling have been properly carried
out, but with some 'prints' great trouble is experienced in getting rid of certain
colours, due to the so-called fadeless dyes in use for printing shirtings and
such-like textiles.
It is the practice in some mills to run the bleached stock into steeps or
drainers and there to allow the bleach to exhaust itself This method has the
advantage that it allows the bleaching in the potcher to be more rapidly carried
out, and it also enables the whole of the bleaching action of the liquor to be