Surface Performance / Exposure / Visual Grade
How Is Pilling Resistance Tested in Knitwear?
A pilling grade describes one specimen after one named exposure. Method, duration, preparation, and rating conditions determine what that grade can mean.
Pilling resistance in knitwear is tested by exposing conditioned specimens to controlled rubbing or tumbling, then visually comparing the resulting surface with the relevant standard photographs or descriptive scale. ISO 12945 provides separate procedures for the pilling box, modified Martindale, and random-tumble methods, followed by a visual assessment procedure. ASTM D4970 covers modified Martindale testing and ASTM D3512 covers random-tumble testing. The methods are not interchangeable: a valid result states the standard and edition, apparatus, specimen preparation, exposure stage or cycle count, any pretreatment, and the observed grade. On the common five-grade scale, 5 indicates no or minimal change and 1 indicates severe pilling, but a passing grade must come from the product specification rather than from a universal rule.
Pilling, fuzzing, and matting are related but different
Pilling is the formation of small fibre entanglements retained on the fabric surface. Before a stable pill forms, fibre ends can work out of the yarn and produce fuzzing. Repeated agitation may also compress or entangle the raised surface into matting. ISO 12945-4 addresses visual assessment of all three effects because a specimen can become visibly rough or flattened without developing a high count of discrete pills.
The mechanism begins with friction, but it is not determined by friction alone. Fibre length and strength, yarn twist, hairiness, blend composition, yarn structure, stitch density, loop length, brushing, washing, finishing, and the ability of an anchor fibre to retain a pill all influence the sequence. A weak fibre may release readily yet shed the pill; a stronger component can keep the entanglement attached. The companion note on why knitwear pills examines those material causes. The test discussed here concerns how surface change is produced and graded under controlled laboratory conditions.
Pilling resistance is also not the same property as abrasion resistance. A modified Martindale pilling procedure may use equipment related to an abrasion tester, but its pressure, movement, abradant, mounting, exposure, and endpoint follow a pilling method. An abrasion-resistance result records breakdown under another procedure and cannot replace a pilling grade.
One grade, one method
“Grade 4” is incomplete. Record whether it followed a pilling-box, modified Martindale, or random-tumble exposure, and identify the assessed stage and product state.
Choose the test method before setting the grade
Rotating pilling box
ISO 12945-1 mounts specimens on polyurethane tubes and tumbles them in a cork-lined rotating box for prescribed periods. The construction allows the mounted fabric surfaces to contact the box lining and one another while the tubes move freely. It is widely associated with knitted and woven apparel fabrics, but the applicable product specification still needs to state the exposure stages and any preparation. Seam position, specimen face, mounting tension, and tube condition can affect the result.
Modified Martindale
ISO 12945-2 and ASTM D4970 use a controlled rubbing action in a modified Martindale arrangement. Circular specimens move in a defined Lissajous path against a specified fabric or against paired specimens under low pressure. This creates repeatable multidirectional surface agitation. The operator observes the specimen at the required intervals rather than running automatically to one universal endpoint. Despite the machine name, the setup must not be treated as a Martindale abrasion test.
Random tumble
ISO 12945-3 and ASTM D3512 place prepared specimens in a cylindrical test chamber where air agitation makes them tumble against a cork lining and one another. The method can suit many woven and knitted fabrics, including some napped surfaces. It is not appropriate when a specimen cannot tumble freely. Chamber condition, cork renewal, air pressure, specimen preparation, and the specified exposure time all belong to the result.
Methods produce different mechanical histories, so a grade from one apparatus should not be converted into a grade from another. A client manual, recognised product standard, or established internal correlation should select the procedure. Where no method is prescribed, development teams should compare the candidate fabric, intended use, and existing approval history before creating a requirement.
Sampling and conditioning control comparability
Specimens should represent the production material and avoid selvedges, damaged areas, folds, or local anomalies unless those anomalies are the subject of the investigation. The sampling plan records roll, panel, colour, yarn and dye lot, finishing batch, face, course and wale directions, and garment stage. Multiple specimens are normally taken because knitted surfaces vary and because a single local result cannot describe a full lot.
Conditioning under the laboratory atmosphere required by the governing method allows moisture-sensitive fibres and structures to reach a more stable state before exposure and rating. ASTM D1776 provides general textile conditioning practice used by many ASTM procedures. Conditioning does not make all specimens identical; it removes an avoidable source of variation from comparison.
Pretreatment must be explicit. Laundering, dry cleaning, brushing, steaming, pressing, or relaxation can change fibre projection and dimensional state. Testing “as received” and testing after a care cycle answer different questions. If a specification requires both, each state should receive its own result. A production sample should not be compared with a washed development swatch as though preparation were immaterial.
Exposure stages and visual rating belong together
The laboratory stops or inspects specimens at the stages stated by the method or specification. There is no universal cycle count suitable for every construction. A result at an early checkpoint may reveal rapid fuzz formation, while a later stage may show pill retention, shedding, or matting. Reporting only the final number can conceal this progression when the specification calls for intermediate observations.
After exposure, specimens are assessed in the specified viewing arrangement under controlled illumination. The evaluator compares them with the applicable photographic standards or written descriptions. On the usual scale, grade 5 represents no change or negligible change, grade 4 slight change, grade 3 moderate change, grade 2 severe change, and grade 1 very severe change. Half grades should be used only when the governing procedure permits them.
Visual assessment contains human judgement, so lighting geometry, viewing distance, specimen orientation, reference set, and assessor training matter. Two evaluators may be required, with disagreement resolved according to the laboratory procedure. Loose fibres should not be casually removed before rating. The report should state whether pilling, fuzzing, and matting were each considered and should note unusual colour change, abrasion, wrinkling, or distortion rather than forcing every surface event into the pilling number.
A laboratory grade is not a forecast of every wearer
A controlled test ranks materials under a defined exposure. Real garments encounter variable pressure, humidity, body movement, bags, seat belts, outerwear, laundering, and wear duration. Flat specimens do not fully reproduce seams, ribs, pockets, underarms, side panels, elbows, or layered contact. The test can support comparison and production control, but it cannot promise that pills will never appear.
A high grade at a short exposure is not automatically stronger evidence than a slightly lower grade at a longer prescribed exposure. Nor does grade 5 mean that the fabric is generally superior: a finish that temporarily suppresses fibre movement may alter softness, loft, colour, or recovery. Surface performance must be read with the intended handle and construction. The note on fabric-hand evaluation explains why softness and surface mobility should not be reduced to one mechanical result.
There is no universal pass grade. A fine-gauge base layer, brushed luxury knit, dense outerwear structure, and sculptural hand-knit do not share one use condition or one acceptable surface. The requirement should reflect product category, intended care, risk area, client standard, benchmark garment, and stage of approval. Method repeatability and laboratory uncertainty should also be considered when a result sits on the limit.
Use the test to locate a process decision
Development testing is most useful when it remains linked to yarn and process variables. Record fibre composition and length distribution, yarn count and twist, ply, spinning system, stitch structure, loop length, gauge, take-down, washing, milling, raising, shearing, softener, pressing, and final dimensions. If a grade changes, this record helps distinguish material substitution from knitting or finishing drift.
A trial can compare controlled alternatives: a tighter or longer loop, revised twist, another brushing intensity, a changed washing route, or a finish adjusted within the desired handle. Change one principal variable at a time where possible. Then confirm the selected route on a full panel and a complete garment, because seams, joining, rib tension, and local friction zones can expose behaviour absent from a small swatch.
Bulk verification should use the same method, preparation, exposure, and rating basis as approval. Anne's Process sets stitch development, sampling, fitting, finishing, and factory handoff within a traceable sequence. Material outcomes can be reviewed in Work; the technical role is outlined in About. Product-specific requests can be directed through the contact form.
Write the pilling requirement so it can be repeated
A complete specification states the standard and edition, apparatus, specimen face and direction, number of specimens, conditioning practice, pretreatment, mounting materials, load or pressure where relevant, exposure stages, assessment standard, permitted grading increments, and minimum result at each required stage. It also defines whether the requirement applies to fabric, garment panels, finished garments, or all three.
The report should identify the sample and lot, colour, product state, date, laboratory, deviations, individual grades, calculated or agreed overall grade, and observations for fuzzing or matting. Reference photographs of the tested specimens can support traceability, although they do not replace assessment under the standard viewing conditions. When buyer and supplier results differ, a pre-agreed referee laboratory and method prevent the dispute from becoming a comparison of incompatible procedures.
Common questions about knitwear pilling tests
What does pilling grade 5 mean?
It means no visible change or negligible pilling under the named method and exposure stage. It does not mean the garment can never pill in wear.
What does grade 1 mean?
Grade 1 represents very severe surface change on the standard five-grade scale. The report should still state the method, stage, and whether fuzzing or matting accompanied the pills.
Is the pilling box better than modified Martindale?
Neither is universally better. They create different exposures. The appropriate method is the one required by the product specification or supported by a relevant correlation for that construction and use.
How many cycles should a pilling test run?
There is no universal count. The governing standard, client manual, or product specification defines the inspection stages or duration. A cycle count without the method is not a complete requirement.
Is a pilling test the same as an abrasion test?
No. Even when a Martindale platform is used, the specimen mounting, counterface, pressure, motion, duration, and assessment differ. Abrasion and pilling require separate results.
Can washing improve or worsen the result?
Yes. Care can remove loose fibre, raise the surface, relax the structure, or change a finish. The result must state whether the specimen was tested before or after a defined care procedure.
A useful pilling result preserves its conditions
Pilling resistance becomes comparable when the specimen, preparation, apparatus, exposure, viewing system, and acceptance point are fixed. Removing any one of those conditions turns a grade into an impression rather than a specification. Preserving them allows development and production teams to connect visible surface change to a material or process decision without claiming that a laboratory chamber can reproduce every garment life.