To the length and width which the finished product is to have, we must add
a certain allowance for shrinkage and _taking up_ of warp during weaving.
It may differ from one to ten per cent., according to the texture and weave
of the fabric, and can be ascertained with sufficient accuracy by
stretching out and measuring a thread of warp and filling and comparing
their length with the respective measurements of the sample to be
reproduced.
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3. THE STOCK AND ITS DYE
Under this heading we must give the particulars as to nature, _twist_,
_quality_ and _size_ of the silk, and the directions for the dyeing,
whether _bright_ or _souple_, and in what colors, also whether to be
weighted or not.
The size is generally ascertained (in practical work) by comparing it with
other silk of which the exact count is known. Another method is to count
the number of cocoon threads which a thread of the sample contains, adding
to that 1/3 or ¼, according to the quality of the silk; the result will be
the count in deniers. To obtain it in drams, divide the latter number by
17,3 as 1 dram is equal to 17,3 deniers.
Suppose we find 20 cocoon ends in a thread of silk: add 1/3, and we have
26-2/3 deniers, which, divided by 17,3 make 1,54 drams.
As silk is always more or less uneven, it is safer to count the cocoon
fibers of several threads and to take average thereof.
It requires the experience of years to judge with any degree of certainty
as to the origin and quality of silk, whether it be "classical," "extra,"
"sublime," etc.
There are machines wherewith to ascertain exactly the twist, that is, the
number of turns the silk has received in the throwing process.
In the dyeing we distinguish two great classes, of which the names
themselves give a good definition. "Bright" has a brilliant luster, while
"souple" has more of a dull, subdued appearance. To find out whether the
silk has been weighted in the dyeing process, we may compare it with other
silk of which the exact conditions are known, or we may burn a small
quantity of it. Unweighted silk does not burn readily and leaves a residue
of white ashes, while heavy weighted silk burns lively, leaving black,
charry ashes.
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4. REED CALCULATION
We count the number of repeats of the weave in a given space, generally ¼
or ½ inch, and multiply this with the number of threads one repeat
contains, which gives us the reduction of the warp.
Suppose we had a taffeta, which, as we know, has only 2 ends to a repeat,
and counted 30 interlacings per ¼ inch on one pick; we would have 60
threads per ¼ inch or 240 per one inch. In this case the reed may be 80 by
3 or 60 by 4.
Another instance: In an 8-shaft satin we count 10 warp-threads, which bind
on the same pick in ¼ inch; this, multiplied by 8, equals 80 ends per ¼, or
320 per one inch; the reed will be an 80 with 4 in a dent or a 64 by 5.
In short, the number of the reed is found by dividing the number of
warp-threads that are to go in one dent, in the number of ends per inch.
Sometimes, the reed marks are clearly visible in a sample by holding the
latter against the light. Silk fabrics move with very few exceptions within
the limits of 50 and 90 dents per inch.
To learn the full number of dents required for the width of the cloth,
simply multiply the dents per one inch with the width, adding a certain
allowance for shrinkage. The edges, of course, must also be taken in
consideration, and very often the dents that are taken up by the latter are
used to counter-balance that shrinkage.