Holes, needle lines, barré and skew are everyday quality problems in weft knitting, on both circular and flat machines. The same fault can have more than one cause, so diagnosis starts with what the cloth looks like and then works back to the yarn, the needles and the settings.
ASTM D3990 is the ASTM terminology standard for defects in woven and knit fabrics. The official store page confirms that scope; it does not publish the individual definitions. The descriptions and remedies below come from Cotton Incorporated’s Defects Glossary on CottonWorks, and from the technical bulletins TRI 3015 (holes), TRI 1002 (barré) and TRI 2002 (skew, torque and spirality). TRI 2007, on machine setup, is written for circular machines. The published examples are mostly circular, though the same yarn, needle and tension checks apply on a flat-bed machine.
Yarn count, machine gauge and stitch length belong together when you judge whether a yarn is too coarse for the hook; see Yarn Count Systems Explained. Fabric mass is GSM. The structures in which these faults most often appear are compared in Single Jersey vs Rib vs Interlock. Start with direction: CottonWorks classifies many knit defects as vertical, wale-direction faults or as horizontal, course-direction faults. Isolated defects sit in one place; finishing defects may appear only after compaction, dyeing or tentering. For laboratory tests more generally, see Fabric Testing: Methods, Equipment and What Results Mean.
Holes
A hole is an opening where yarn has been broken, cut, or prevented from interlooping. CottonWorks records two knit examples: a lint ball interfering with interlooping in a double knit, and fabric “pulverised” during compaction in a single knit. TRI 3015 adds that holes are often first seen at garment inspection, so the cause may lie in knitting, later physical damage, or chemical damage during bleaching or finishing.
Yarn-related causes in TRI 3015 include a yarn too coarse for the gauge or hook; thick and thin places; yarn too weak for the tightness, tension and stitch length in use; twist so high that the yarn kinks; poor knots or splices, including long tails that double or triple the diameter; excessive hairiness; and high trash. If the stitch length is too short, the extra stress can make holes; if it is too long, drop stitches are more likely than holes. Machine causes include high yarn tension; a feeder timed too early or too late; a creel or path that rubs the end; take-down tension that is too high, or so low that previous loops ride up; worn or bent hooks, worn cams, and dials or cylinders out of centre; and incorrect sinker or cylinder-to-dial timing. After knitting, fabric can be snagged, over-spread, pinched in a compactor, or cut by sewing needles. Chemical damage includes over-activation of hydrogen peroxide by iron, over-processing, and over-crosslinking with resin.
Prevention follows the same list: match yarn count to gauge, reject serious thick or thin places, keep twist within the bulletin’s suggested ranges (a twist multiple of 3.2 to 3.8 for ring-spun cotton and 3.6 to 4.2 for open-end; higher twist can cause problems), tie knots correctly, keep the yarn path clear, and keep needle beds clean and properly lubricated. To examine a greige hole, look under magnification, count how many yarns are broken or separated, and decide whether a yarn looks cut or pulled apart. A hole on one wale points to that needle; more than one hole on the same wale is a reason to check the knitting elements.
Dropped stitches
CottonWorks defines dropped stitches, in double-knit examples, as stitches that fail to form because of a malfunctioning needle or jack. They are warp-line, vertical defects. They are not the same as a press-off, in which needles cease to function and the fabric falls off a circular machine or the design is destroyed.
TRI 3015 links drop stitches to thick and thin yarns, twist liveliness, poor knots or splices, and hairiness with lint build-up. Stitch length that is too long makes drop stitches more likely than holes. Yarn tension that is too low, or a feeder timed too early or too late, can leave the yarn badly positioned and produce either holes or drop stitches. The remedy is to replace or repair the needle or jack, clear wax and lint from guides, and correct stitch length, feeder timing and input tension. On patterned machines, treat random dropped stitches as a selection problem as well; that case is covered under tuck and miss faults below.
Needle lines and runs
CottonWorks defines a needle line, in a double-knit example, as the result of a bent needle. It is a vertical, wale-direction fault. A closely related defect is a run: a vertical line of unformed stitches from a broken needle or jack, shown on single-knit fabric and listed as a major defect. TRI 1002 adds that worn needles generally produce length-direction streaks, and that uneven cylinder-height needles can produce wavy barré, so a vertical line may also be a needle that is worn, badly seated, or of a different height from its neighbours.
Replace the damaged or worn needle, and check neighbouring needles, latches and tricks at the same time. A scheduled needle check during style changes, the subject of TRI 2007 for circular machines, stops one bad needle from marking a whole roll.
Barré and streaks
Cotton Incorporated, citing ASTM terminology in TRI 1002, defines barré as an unintentional, repetitive visual pattern of continuous bars and stripes, usually parallel to the filling of a woven fabric or to the courses of a circular-knit fabric. In a warp knit, barré normally runs in the length direction, following the yarn. A barré streak can be one course wide or several courses wide, a “shadow band”.
CottonWorks gives two weft-knit examples that produce a barré appearance: a coarse yarn at one feed, and a machine that continues to run with one yarn broken or missing. Both are weft-line, horizontal defects. A related appearance is a fine yarn or a loose course, which can look like fine width-wise cracks and can be hard to tell apart on the back of a single knit.
TRI 1002 sums up the causes in one word: inconsistency. In the fibre, that can be poor control of diameter or colour, or too high a coefficient of variation of micronaire in the laydown. In the yarn, it includes mixing counts, spinning systems, blend levels, suppliers, twist, hairiness or wax, and differences in mercerisation or conditioning. In knitting, the bulletin lists improper stitch length or tension at a feed, variation in fabric take-up, excessive lint, variation in oil content, worn or uneven-height needles, and a double feed end.
To investigate, examine both sides on a flat table, then view the cloth under fluorescent and ultraviolet light, which makes mineral oils easier to see. Record the frequency, direction, light or dark character, and repeat length of the streaks. An Atlas Streak Analyzer impression can help to separate physical streaks from dyeability differences. If the cause looks physical, compare twist and linear density in light and dark courses, and use microscopy to check for mixed spinning systems or mixed S and Z twist. Prevention is consistency: keep lots apart, and equalise stitch length and tension at every feed.
Spirality or skew
Cotton Incorporated’s TRI 2002 treats skew, torque, spirality, bias and shear distortion as names for the same phenomenon: knitted wales and courses angularly displaced from a right angle. If the wales lean from the vertical, the bulletin calls it wale skew; if the courses lean from the horizontal, it is course skew. The displacement can be expressed as a percentage or as an angle in degrees. A figure in that bulletin labels wale skew as the result of wale loop distortion.
Cotton single jersey is particularly prone to this when it is allowed to relax. Causes in TRI 2002 include yarn twist and twist liveliness, twist direction, the spinning system, stitch tightness, the number of feeders, the rotational direction of the knitting cylinder, and the finishing techniques used. In tubular goods, yarn-related skew often appears as wales spiralling around the tube while the courses stay closer to the horizontal. The bulletin’s practical conclusion is that the best answer is either plied yarns or alternating feeds of opposite twist. If singles yarns must be used, resin finishing is said to offer reasonable control. AATCC lists Test Method 179, Skew Change in Fabrics After Home Laundering; TRI 2002 includes it as an appendix. Official AATCC pages confirm the title, not the procedure.
Oil spots
CottonWorks describes oil spots as deposits of oil that have fallen onto the fabric from some processing step. They are typically round or tear-drop in shape, but they can be irregular.
TRI 1002 lists variation in oil content among the knitting-machine causes of barré, and notes that mineral oils glow under ultraviolet light. Streaks that glow under UV light suggest improper preparation, which can happen when a spinner or knitter changes the oil or wax without a matching change in scouring. TRI 3015 asks for proper lubrication of needle beds and knitting elements, which reduces fabric-forming stresses and wear, together with cleaning to avoid lint, grime and yarn wax. Lubricate the machine correctly, keep oil off the cloth, and make sure preparation can remove the oil and wax actually on the yarn.
Slubs and thick or thin yarn
CottonWorks defines a slub, on single-knit fabric, as a short, thick or heavy place in the yarn. It is an isolated defect. A different, width-wise appearance is a coarse yarn at one feed, already mentioned under barré, or a fine yarn that can resemble a loose course.
TRI 3015 treats thick and thin yarns as a cause of variable tension, holes and drop stitches, and tells the knitter not to use yarn with high imperfections, especially very thin or thick segments. Check yarn quality in the fabric and in inventory when holes look as if the yarn has been pulled apart at a thick or thin place. The remedy sits mainly in the yarn: clearer winding, agreed limits on slubs and thin places, and not mixing lots at the creel. A slub already knitted in has to be cut out or downgraded.
Tuck and miss faults
A tuck is not always a fault. In a piqué or other designed structure it is an intentional stitch, as explained in the jersey, rib and interlock article. It becomes a defect when it is unintentional.
CottonWorks defines unwanted tucking as the result of a malfunctioning needle. Tucking occurs when a needle retains one loop, takes on one or more additional loops, and then casts all of them together. A related single-knit defect, birdseye, is the result of erratic and unintentional tucking caused by a malfunctioning needle. A skip stitch, in a double-knit example, is the result of a stuck jack that fails to actuate the needle, so a stitch is skipped. When the yarn is picked up for the next stitch, a float is formed on the face of the fabric. Mis-selection is described as a pattern corrupted by the random dropping of stitches, which may be the result of sticking jacks or erratic yarn feed.
Replace or free the needle or jack, clear the tricks, and check that the intended cam or selection path is actually being followed. If the fault is isolated to one wale, start with that needle. If stitches are dropped at random across a pattern, look at jacks, selection and yarn feed together.
Pin holes and other small holes
In the CottonWorks glossary, pin holes are a finishing defect: holes resulting from running the fabric over a pin tenter, when the pins venture too far in from the selvage and distort or tear the fabric.
Small holes in knitted fabric are often something else, and they should not be assumed to be tenter pins without evidence. TRI 3015’s greige examination is the right way to tell a single-needle problem, a thick or thin yarn, a lint ball, or later mechanical damage from a pin-tenter mark near a selvage. Compactor damage, also listed by CottonWorks as a hole in single-knit fabric, is a finishing cause rather than a knitting one.
Loop distortion
TRI 2002 uses “wale loop distortion” for the lean of wales that produces wale skew, already discussed under spirality.
A different kind of loop movement appears in finishing. In Cotton Incorporated’s ISP 1009 shrinkage guide, corrugation or wrinkling of the surface because of improper loop movement during compaction is a known finishing defect. CottonWorks records compactor creases on single-knit fabric when wrinkles on a folded tubular selvage are compressed into hard creases. Those are not knitting faults, but they can be mistaken for them if greige cloth is not inspected first. Use plied yarns or alternating twist to limit spirality, avoid mixing S and Z lots, and set the compactor so that loops are compressed evenly.
A quick fault-finder
Confirm the direction of the fault, then test the most likely cause first. This table is a starting point, not a substitute for looking at the cloth.
| What you see | First places to look | Typical correction |
|---|---|---|
| Isolated hole; yarn pulled apart | Thick or thin yarn, knot, splice, lint ball | Check yarn quality; clear lint; review tension and stitch length |
| Hole or holes on one wale | Bent, worn or damaged needle | Replace the needle; check neighbouring elements |
| Hole after finishing, near a crease or selvage | Compactor pinch or pin tenter | Reset the compactor or pin line; inspect greige cloth first |
| Vertical dropped stitches or a run | Needle or jack not knitting; stitch length too long; tension too low | Repair the element; correct stitch length, feeder timing and tension |
| Fine vertical line (needle line) | Bent or worn needle; uneven needle height | Replace and equalise needles |
| Horizontal bars or a shadow band (barré) | Mixed yarn lots; stitch length or tension at one feed; oil or wax | Segregate lots; equalise feeds; use UV if oil is suspected |
| Fine width-wise crack | Fine yarn or a loose course | Check that feed’s yarn and stitch cam |
| Wales leaning; garment twists after washing | Yarn torque; single jersey; finishing tension | Ply or alternate twist; relax without adding torque |
| Round or irregular oil mark | Oil from a processing step | Correct lubrication; improve preparation |
| Short thick lump (slub) | Yarn irregularity | Improve clearing; do not mix packages |
| Unwanted tuck, birdseye, float or broken pattern | Malfunctioning needle or stuck jack; erratic feed | Repair the element; check selection and yarn feed |
FAQ
Is a hole always a knitting fault? No. TRI 3015 distinguishes knitting causes from later physical damage, such as snagging, over-spreading or compacting, and from chemical damage in bleaching or resin finishing. CottonWorks also records holes created by lint during knitting and by compaction.
How do I tell a needle line from a dropped-stitch run? A needle line, in the CottonWorks double-knit example, is the result of a bent needle and may be a relatively fine vertical mark. A run is a vertical line of unformed stitches from a broken needle or jack. Both follow a wale.
Why does barré sometimes appear only after dyeing? TRI 1002 states that barré can be caused by physical, optical or dye differences in the yarns, by geometric differences in the fabric, or by a combination. Dyeing can reveal a difference that was already present. Ultraviolet light can show mineral oil.
Do these faults occur on flat machines as well as circular ones? Yes, in principle. A bent needle, a thick place in the yarn, a bad knot, or a wrong yarn tension will mark a V-bed fabric as surely as a circular one. The published examples are mostly circular; apply the same checks on a flat machine.
Can I correct spirality in finishing alone? Finishing can relax the fabric and, if singles yarns must be used, TRI 2002 says resin finishing offers reasonable control of skew. The same bulletin still puts the best answer in the yarn: plied yarns or alternating feeds of opposite twist.
Sources
- ASTM D3990-12(2020), Standard Terminology Relating to Fabric Defects (official scope: defects in both woven and knit fabrics).
- CottonWorks Defects Glossary (Cotton Incorporated), including the individual entries Needle Line (0179), Run (0174), Dropped Stitches (0189), Hole (0183), Hole (0184), Slub (0182), Tucking (Unwanted) (0185), Birdseye (0178), Skip Stitch (0186), Mis-selection (0187), Coarse Yarn (0172), Missing Yarn (0173), Fine Yarn - Loose Course (0191), Press-off (0192), Oil Spot (0132), Pin Holes (0147) and Compactor Creases (0181).
- Cotton Incorporated, TRI 3015, Guide to Evaluating and Reducing Holes in Knitted Fabrics (2002).
- Cotton Incorporated, TRI 1002, Barré (1992).
- Cotton Incorporated, TRI 2002, Knit Fabrics and the Reduction of Torque (2001).
- Cotton Incorporated, TRI 2007, Weft Knitting Style Change-Over and Machine Setup Procedure (2004).
- Cotton Incorporated, ISP 1009, A Guide to Improved Shrinkage Performance of Cotton Fabrics (2004): compaction defects from improper loop movement.
- AATCC, Standard Test Methods and Procedures: listing for AATCC TM179, Skew Change in Fabrics After Home Laundering.
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