Knit fabrics fail in ways that woven fabrics never will — because knit construction is a network of interlocked loops rather than a grid of crossing threads, and every loop carries residual stress that can rotate, curl, or grow the moment the fabric is relaxed, washed, or cut. A spirality angle that looks acceptable in the roll can twist a side seam 6 cm off-centre after one wash. A fabric that passes stretch testing can grow 8% in garment wear without triggering any standard test. These failures are invisible to woven-fabric protocols and to inspectors who do not know what to measure. This guide covers the four tests that matter most for knit quality — spirality, curling, stretch recovery, and growth — with the measurement procedures, the standards that govern them, the tolerance thresholds, and the root causes behind each defect. Teams managing knit quality programmes can book a 30-minute demo to see how iFactory tracks these parameters in real time.
Knit Fabric Testing — Spirality, Curling, Stretch Recovery, and Growth
Four knit-specific quality tests that woven-fabric protocols miss entirely. Measurement procedures for each, the AATCC and ISO standards that govern them, industry tolerance thresholds by fabric type, and the causes behind each failure — with the defect decision matrix for incoming inspection.
Spirality (AATCC 179): ≤5° acceptable, >5° conditional, >8° reject. Curling: inherent in single jersey, critical in double jersey. Stretch recovery: ≥90% for activewear, ≥85% for casualwear. Growth: ≤3% acceptable in garment wear. Courses per inch and wales per inch: measure before any other test — density drives all other knit properties.
Why Knit Testing Needs Its Own Protocol
Knit fabric is dimensionally unstable in ways woven construction is not. Three root causes explain every knit-specific test on this page — and why applying a woven-fabric protocol to a knit will miss every one of them.
Loop Structure = Residual Torque
Every knit loop carries the residual torque of the yarn that formed it. On a circular knitting machine with multiple feeders, yarn twist direction and machine rotation combine to create a systematic bias that rotates the entire fabric — the structural origin of spirality.
Free Edges = Bending Moment
At any cut or selvage edge, loops are no longer restrained by adjacent loops. Yarn bending stiffness pulls the edge toward its natural curvature, causing curl. In single jersey, selvage edges curl toward the technical back; cut edges curl toward the technical face.
Loop Mobility = Growth Under Load
Unlike a woven thread locked at every intersection, a knit loop can slide within the fabric under sustained load. This migration does not fully recover when load is removed — producing permanent elongation known as fabric growth.
Test 1 — Spirality (Skewness)
Spirality is a specific technical defect prevalent in single-jersey circular knits that manifests as a diagonal displacement of the garment's side seams. It is measured as the angle by which the wale or course line deviates from vertical or horizontal. It is the single most common cause of garment twist rejection in knit T-shirts and polos.
Root Causes and Corrective Actions
The causes of spirality divide into material causes — primarily residual torque in the yarn from twist-liveliness — and process causes connected with knitting on multiple feeders on circular machines. Yarn-side fixes include selecting low-torque or torque-balanced constructions; process-side fixes include adjusting feeder count or knitting direction. Anti-torque yarn finishing is the most reliable long-term solution for chronic spirality.
Test 2 — Fabric Curling
Single-jersey fabric is the most prone to edge curling. Selvage edges typically roll toward the wrong side, while cut edges curl toward the right side. Curling is inherent to single-jersey construction — a design consequence rather than a defect — but its severity must be quantified because it determines cutability, handling efficiency, and pattern accuracy in CMT operations.
Where Curling Occurs and Why
Curl Severity by Construction
Curl is measured as the depth (in mm) to which the edge rolls over a flat reference surface under zero tension after a 30-minute relaxation period. Acceptable curl depth is typically less than 15 mm on undyed fabric and less than 10 mm after dyeing and finishing, where compaction and anti-curl finishing should have reduced the raw curl.
Test 3 — Stretch and Recovery
Stretch and recovery are two separate measurements often confused. Stretch percentage describes how far a fabric extends under load; recovery describes how much of that extension returns when the load is removed. Both matter, but for different end-uses and at different specification levels.
Cut 200 mm × 50 mm in both directions. Mark two reference lines 100 mm apart at specimen centre. Condition at 21°C, 65% RH for 4 hours.
Apply load per standard (0.5 kg low-power, 2.3 kg higher-power). Measure distance between reference lines under load. Stretch % = (extended − original) ÷ original × 100.
Remove load. Allow 60-second recovery. Re-measure reference lines. Recovery % = (stretched − recovered) ÷ (stretched − original) × 100.
Test course and wale directions independently. Four-way stretch fabrics must meet specification in both directions independently.
| End Use | Min Stretch % | Min Recovery % | Typical Elastane % |
|---|---|---|---|
| T-shirts / casual tops | 25 – 40% | ≥ 85% | 0 – 3% |
| Fitted activewear | 50 – 75% | ≥ 90% | 5 – 10% |
| Compression / sports | 75 – 100% | ≥ 95% | 15 – 25% |
| Swimwear / leotards | 100%+ | ≥ 98% | 20 – 30% |
| Underwear / base layer | 40 – 60% | ≥ 90% | 5 – 8% |
Test 4 — Fabric Growth
Growth is permanent extension — the residual elongation that remains after a fabric has been stretched in wear and the tension removed. Unlike recoverable stretch, growth accumulates over the life of the garment. Certain heavy-rib knits can grow or elongate in length while shrinking in width — a phenomenon known as the Poisson effect in textile geometry. Growth testing simulates repeated wear cycles and measures permanent elongation after each cycle.
Density Testing — The Prerequisite for Every Knit Test
Before any of the four tests above are meaningful, fabric density must be measured. Courses per inch (CPI) and wales per inch (WPI) determine the stitch architecture that drives every knit property. A batch with CPI or WPI outside specified tolerance will fail downstream tests for structural reasons, not material ones.
Knit quality testing is not woven testing with a different fabric. It is a different test list entirely.
Spirality, curl, growth, and recovery require knit-specific protocols that most incoming inspection programmes do not include. iFactory's quality module covers all four with roll-level tracking, tolerance flagging, and defect trend analysis. A 30-minute demo builds a live knit quality dashboard against your incoming specification.
Frequently Asked Questions
Is fabric curling a defect or a feature of single jersey?
It is inherent to single-jersey construction — a consequence of the structure rather than a manufacturing defect. Edge curling is a feature of single-jersey construction, not a defect. The issue arises in CMT operations where severe curl reduces usable cutting width, causes pattern misalignment, and slows automated cutting equipment. The threshold — typically less than 15 mm curl depth in the relaxed state — is a handling-efficiency limit rather than a quality limit. Anti-curl finishing, compaction stentering, and fabric relaxation before cutting are the three controls that manage curl to workable levels. If curl consistently exceeds 20 mm, check whether stitch length is outside specification — excessive loop size increases the bending moment at the edge. Contact iFactory Support for a curl control procedure.
What is the difference between spirality and skewness in knitted fabrics?
Skewness in a woven fabric refers to weft deviation from perpendicular to the warp — a thread-line angle. Spirality in a knit refers to the rotation of the entire loop structure around the fabric's vertical axis — a fabric-wide torque. Weft-knitted structures are affected by loop inclination (skewness) and structural rotation (spirality) — related but distinct distortions. AATCC 179 measures the combined result in washed fabrics as a single skewness angle because in garment practice both manifest as twisted side seams. Use spirality as the production term and AATCC 179 as the test reference.
Can spirality be corrected after knitting?
Partially. Relaxation, compaction, and stentering can reduce spirality by allowing residual torque to discharge before dyeing and finishing. These processes address fabric stress but do not remove the yarn's underlying twist liveliness — meaning spirality can re-emerge after laundering. The only durable correction is at the yarn stage: using low-torque, torque-balanced, or anti-twist-treated yarn. For persistent post-wash spirality, check whether yarn twist direction opposes the knitting machine rotation direction — this combination systematically increases spirality and cannot be fixed by finishing. Book a demo to see how iFactory tracks spirality by yarn lot.
What causes a fabric to have good stretch but poor recovery?
Recovery is driven primarily by fibre and yarn elasticity, not knit structure alone. A cotton single jersey without elastane typically achieves 25 to 40% stretch but returns to only 80 to 85% of its original length — the remainder is permanent growth accumulating over wear cycles. Adding 3 to 5% elastane raises recovery above 90% because the elastane filaments act as recovery springs. Loop length also matters: longer loops increase stretch but reduce recovery because the filament has more travel before it reaches its elastic limit. Always specify both minimum stretch and minimum recovery — reporting stretch alone is insufficient for fit-critical garments.
How should knit fabric be conditioned before testing?
Conditioning is not optional — moisture content changes the relaxation state of knit loops and shifts every measurement. The standard environment is 21°C ± 2°C and 65% RH ± 4% for a minimum of 4 hours, per ISO 139 and AATCC 79. Fabrics from the knitting machine or finishing line should be relaxed flat for at least 24 hours before conditioning begins — machine tension holds loops in a distorted state that takes time to discharge. Fabrics tested without adequate conditioning typically show 10 to 30% lower spirality and 5 to 10% higher recovery than the same fabric after conditioning, producing falsely optimistic results. Contact iFactory Support for a standard incoming inspection conditioning procedure.
Track spirality, curl, recovery, and growth by roll — before they become garment rejections.
Roll-level knit quality data — CPI, WPI, spirality angle, curl depth, stretch percentage, recovery percentage, and growth — logged against supplier, machine, yarn lot, and finish batch. iFactory gives quality teams the trend data to reject upstream before cutting, not after make. A 30-minute demo builds the live quality view on your incoming roll data. Sessions available this week.
