DEFECTS IN FABRICS
In a former chapter the intricately delicate structure of the knitted
loops was described, and the causes of some of the minor defects of
stitch were outlined when the utmost importance of a regular feed of
yarn to the needles was emphasized. Another important series of defects
in knitted articles are directly traceable to faults in the
stitch-forming parts of the machine, such as the sinkers and needles,
and many imperfections spring from faulty condition or adjustment of
these parts. The needle is perhaps the most delicate part of the frame
and constant attention has to be given to these if perfect knitting has
to be produced. Large firms find it to their advantage to engage an
operative for this special work alone, he inspects all frames and his
trained eye can soon detect the slightest fault of needle alignment and
he replaces faulty needles by casting new ones. The pliaring of needles,
as it is called, is an important part of the work of a modern knitting
factory, and care to these machine parts is at once reflected in the
quality of the fabric produced on the frames. A constant source of
trouble in knitting is the beard or spring of the needle, and if these
are not properly hardened or tempered their period of service is much
shortened, because the beard soon develops faulty action and refuses to
spring back into its former position after the removal of the presser.
If the beard has lost its spring the new yarn cannot be pushed properly
underneath, a common defect being for the stitch to be halved, one
portion of the thread going under and the other half over the spring of
the needle. These split stitches cause small puckerings in the texture
which seriously affect its market value, and when the yarn is split in
this fashion the stitch at this point has only half its strength, the
thread gets broken and a hole is caused in the fabric. Another defect in
the needle occurs when the beard is working out of its true position in
a vertical direction, the beard in place of going straight into the
groove lands a little to the right or the left when it catches the yarn
as it is drawn forward.
[Illustration:
FIG. 58
]
_Sinker and Needle Lines._—Sinker and needle lines are formed vertically
in the fabric and are due to needles and sinkers being out of alignment
in relation to their neighbours. If the needle is raised above or
depressed below the normal level of the needle line, or if it is not in
the exact central position in relation to the needle at each side a
defect will be formed, which will show vertically in the fabric. A
diagrammatic view of this kind of fabric blemish is given in Fig. 58
where the line is marked A and is formed by a vertical series of loops
of larger curves than those around. The sinker line and the needle line
are alike in general appearance except that the sinker line affects the
sinker wales and the needle lines the needle rows. The needle at A has
been pushed a little to the left so that more than normal spacing
occurs, and this causes an extra length of yarn to be served to the
stitch at this point. It might be more correct to say that this extra
length is supplied at the expense of the neighbouring loops at B and C
which are seen to be smaller than the normal. The needle in moving to
the left out of the true central position between its neighbours
enlarges the draw at one point, but makes a corresponding contraction of
the stitch at B where the needle has to be content with a shorter piece
of the yarn. This is the basic reason why these lines are so
conspicuous, the regular spacing of the needles is departed from and
there is always a large-size loop side by side with a shorter and more
contracted stitch. The sinker line may also be caused the same way and
has the same general appearance; if the sinker is not working in its
true central position between two needles there is a variation in the
length of loop which shows a line as before. In the case of the sinker,
the lines may be produced from another cause, and that is the wearing of
the sinker at its throat, the part employed for pushing the yarn between
the frame needles. This wearing of the sinker throat will tend to reduce
the size of the loop at that point, because it will not be able to take
a sufficient length of loop when pushed forward. Similar defects are
caused if the sinker is rough, and another blemish is known as
"cutting," where the yarn is totally or partially cut through as the
sinkers push the yarn between the needles. Cutting may be due to the
push of the sinker being too great, or it may be caused by yarn which is
not strong enough to stand the strain of loop sinking.
_Other Defects._—A very common defect which will prove disastrous if not
remedied is given at Fig. 59, known popularly as a "Jacob's Ladder."
This will be noted to be due to a stitch running down in a vertical
direction and caused in the first place by a breaking of the thread.
Once this severance has taken place the stitch loses its supports and
unravels as long as the least strain is imposed upon it. The method of
repairing this is to take the last perfect stitch in the run and link it
up with the slack thread of the course immediately above until the whole
fabric has been restored, the top stitch being secured suitably to
prevent a repetition of the unravelling. This linking of the stitch can
be done very rapidly by an experienced hand with the aid of a turning
hook which is indispensable for repairing all defects in the knitted
texture. If the loops get severed by a cross cut the process of
repairing the break is much more complicated and requires greater skill
to rehabilitate. The cut loops have to be unravelled to give a perfect
row of stitches on which to base the repair, and the missing courses
have to be entirely rebuilt by the needle of the operative. In
reconstructing those missing stitches, they have to be formed as nearly
as possible of the same size as will correspond to the fabric gauge, and
it requires years of experience for a worker to acquire the ability to
reconstruct the fabric in such a way that the rent will be
imperceptible. In some hosiery districts the saleable quality of their
products is much reduced owing to faulty repairing of cross
imperfections, in many cases the practice prevails of simply drawing the
stitches tightly together and securing them. To repair a large hole in a
knitted structure the usual way is to patch by cutting the broken part
out in the form of a square running directly crosswise with the loops
and directly vertical with the wales of the fabric. The patch is made
from a piece of fabric identical in gauge and texture with the ground
fabric, and the stitches are knitted to each other crosswise at the top
and bottom of the square, a perfect union being possible; vertically the
patch is seamed and joined to the ground fabric by a row of ordinary
sewing which is drawn round to the back of the garment and which, if
skilfully performed, gives but little indication of the blemish. A
worker skilled in this branch of repairing knitted fabrics proves of the
greatest value to any knitting mill, and her efforts result in the
salving of large numbers of expensive garments which might otherwise
have to be disposed of at sacrificial prices.
[Illustration:
FIG. 59
]
[Illustration:
FIG. 60
]
_Slurgalling._—This term is applied to several defects in knitted
fabrics which are the bane of hosiery manufacturing and belong to the
type of imperfections which it is extremely difficult to repair, whilst
in many cases it is not a practical possibility. A few stitches of this
kind of imperfection are given herewith in Fig. 60, which is a
diagrammatic enlargement of the wrong side of the plain knitted loop
where the defect is shown plainly by means of the black coloured
stitches appearing crosswise in the fabric. It consists of a tightening
of the loops due to a momentary increase of the tension of the thread
during knitting; the stitches become constricted and at once injure the
general amenity of the fabric. Even minor variations in yarn tension
will cause these crosswise defects in the cloth, and they are so minute
in their formation that it is almost impossible to repair them. If any
irregularity creeps into the tensioning of the thread as the carrier is
moving from right to left as compared with its motion from left to
right, then the variation in the size of the loops may be perceptible at
alternate courses and occur right across the fabric. Small obstructions
on the yarn surface such as knots, burrs or slubs, will produce a
momentary catch on the aperture of the thread-carrier and cause this
cross constriction of loops; a rough carrier nose is a fruitful source
of trouble if any grooves are being worn in the instrument. In some
machines a worn slurcock may be the cause of such irregularities.
[Illustration:
FIG. 61
]
_Stitches of Variable Symmetry._—These defects are illustrated in
various forms in Fig. 61, which gives a diagrammatic view of the chief
variations which are met with in single stitch formation in the knitted
texture. During knitting the yarn usually forms itself into curved
loops, but various conditions have to be met if this curving has to be
perfect. Should the knitting yarn be lacking in yielding property curves
will not eventuate, but will be replaced by various distorted
formations. Very often the mechanical structure of the yarn makes it
impossible for the thread to fall out in nicely-shaped curves, this
taking place when the constituent fibres are tightly arranged in the
yarn or when they are composed of long fibres drawn with meticulous
precision in parallel order side by side. A much more suitable thread is
worked from shorter materials which gives a freer scope of direction.
This renders the thread less rigid and makes it more amenable to loop
formation, whilst the beneficial effects of lubrication or damping of
dry yarn have already been referred to. Several typical examples of
these deficiencies are illustrated in Fig. 61 by means of the stitches
marked 1 to 4. Stitches 1 and 2 show a mal-formation of loop due to a
straightening of the yarn, the fibres are too long and do not yield in
loop formation. With hard yarns which are thick for the gauge of the
frame, these straightened loops may occur six or eight together and have
the effect of tightening the fabric at that point, at other times they
take up a direction leaning to the right or the left which greatly
impoverishes the goods. The more usual type of mal-formation is given in
loops 3 and 4 where the stitch, unable to content itself with the length
of yarn allotted to it, takes up an enlarged area. These are termed
"pinholes," and when scattered all over a fabric seriously undermine its
value.
Manufacturers are often baffled by a plain fabric issuing from the frame
of the rotary type using bearded needles which shows an effect like 2
and 1 rib, that is, there is a minute opening after every second stitch
which, by its general appearance, resembles 2 and 1 rib, the space
giving the impression of the open part formed by the vertical row of
loops which go to the back of the texture. Wherever this is detected
attention should be given to the dividing of the loops in the machine.
In stitch formation for an average bearded needle machine the loops are
first sunk over alternate needles, and thereafter equalized or divided
over all the needles. When the equalization is not accurately performed,
as is the case when the divider sinkers are not pushed sufficiently
between the needle or are pushed too far, then the ribbed effect will be
produced. Another common defect occurs at the selvedge consisting of a
variable tension of the end loops, some being large and others
constricted. This may be due to the yarn having too much play at the
edge, so that the end two sinkers are permitted to draw more than their
quota of yarn for stitch formation, which makes the edge raw and
unsightly and gives trouble in seaming when the quality of the seam is
variable owing to the different size of loop. The remedy for this
imperfection lies in an adjustment of the snappers which exercise a drag
on the thread just when the end sinkers show a tendency to take more
than their share of yarn.
INDEX
Angora rabbit fur for knitting, 86
Artificial silk knitting yarns, 78
Average counts in knitted web, 50
Bad selvedge, causes of, 134
Bearded needle, function of, 57
—— ——, stitch formation with, 59
Blue, characteristics of, 119
Bobbin building, principles of, 94
Camel hair, uses of, 86
Cardigan rib stitches, 25
Cashmere yarns for hosiery, 85
Check designs in circular frames, 115
Clan hosiery, colour principles of, 120
Colour harmony, principles of, 122
—— contrast, 124
Constants for yarn calculations, 40
Correct texture, essentials in, 74
Cotton knitting yarns, 76
—— and wool mixtures, 83
—— yarns, setting of, 74
Cotton's patent power frame, 65
—— —— —— ——, gauging of, 67
Courses and wales, comparison of, 74
Crochet, hand, 7
Cut-up trade, 12
Damping of hosiery yarns, 96
Defects in knitted colourings, 117
Differential motion in winding, 95
English heel on full-fashioned hosiery, 105
Factory winding, disadvantages of, 91
Fancy trade, requirements for, 88
Flat knitter, technicalities of, 19
Folded yarn calculations, 46
—— thread, to find missing counts in, 53
—— yarns, costing of, 49
Footwear machines, gauges of, 100
Formulae, explanations of, 47
Foster winding frame, 94
French heel on full-fashioned hosiery, 106
Full-fashioned hosiery, manufacture of, 104
Full fabrics, description of, 70
—— -fashioned knitting, 13
Goat hairs, peculiarities of, 87
Green, place of, in knitted goods, 121
Griswold circular knitter, 99
Hand-frame knitting, 61
Hand knitting gauges, 10
Heat-retention, theory of, 5
Horizontal colour stripes, 109
Hosiery, definition of, 5
"Jacob's Ladder" defect, 129
Knitted coats, colouring of, 123
—— fabric, structure of, 1
—— ——, weight calculations, 42
—— ——, length calculations, 45
Knitting, knop effects in, 116
—— and weaving, 9
—— process, 11
—— yarns, wheeling, 27
—— ——, lamb's wool, 29
—— ——, Shetland, 30
—— ——, natural, 31
—— ——, fingering, 33
—— ——, dry-spun, 34
—— ——, counts of, 37
—— ——, mercerized, 78
—— ——, spun-silk, 79
Latch needle frames, loop formation on, 16
Laundering, rules for, 108
Loop length, variations of, 73
Merino fabrics, 84
Natural tints in underwear, 108
Needle lines in fabric, 127
Nettle fibre yarn, 88
Orange, place of, in knitted goods, 120
Patching knitted webbing, 130
Patterns from flat knitter, 23
Pattern styles in knitted goods, 110
Pigment colour theory, 117
Pinholed work, 133
Purple, place of, in knitted goods, 121
Reconstructing broken stitches, 130
Red, characteristics of, 118
Rib stitch, characteristics of, 22
Ribbed footwear, making of, 103
Seamless hosiery trade, 14
Secondary colours, production of, 119
Separating colours, 125
Setting of knitted fabrics, 68
Silk and wool fabrics, 81
—— ——, uses of, 82
Sinker lines in fabric, 129
Slurgalled work, 131
Split stitches, 127
Stitch formation on circular frames, 102
Take-up in knitting calculations, 52
Tuck pressers, 112
—— stitch structure, 114
Vertical striped goods, 111
Washing, precautions in, 107
Weight percentages, 55
Winding of hosiery yarns, 90
Woollen yarns, setting of, 72
Yarn testing for counts, 38
—— conversion calculations, 40
——, variation in setting, 68
—— package, essentials of, 90
—— clearing system, 96
Yarns suitable for frame gauge, 75
Yellow, characteristics of, 118
—— tint in knitted goods, 107
_Printed by Sir Isaac Pitman & Sons, Ltd., Bath, England_
TRANSCRIBER'S NOTES
1. Silently corrected simple spelling, grammar, and typographical
errors.
2. Retained anachronistic and non-standard spellings as printed.
3. Enclosed italics font in _underscores_.