Martindale Abrasion for Bag Fabric: Choosing the End Point, Reading the Rating and Setting a Knit-Specific Acceptance Figure

The Decision Order: Six Choices Before Commissioning a Test

A Martindale result is the output of six choices, and only one of them is the number everyone talks about. In order: whether abrasion is the governing risk at all, which end point the method should measure, which nominal pressure applies, which abradant and change interval, which specimen and direction, and finally what counts as an acceptable result.

Working in that order takes about fifteen minutes and prevents the common outcome, which is a report with a number that is technically correct and commercially silent. A buyer who starts at step six has already skipped the decisions that determine whether the number means anything.

The order also makes the conversation with a laboratory short. A request that arrives with the end point, pressure, abradant and construction already chosen can be quoted and scheduled immediately; one that asks for Martindale testing on a bag fabric generates three rounds of clarification.

Decision 1

Is abrasion the governing failure mode, or does the bag fail on seams, handles or colour first?

Decision 2

End point: breakdown under ISO 12947-2, mass loss under Part 3, or appearance change under Part 4

Decision 3

Nominal pressure: 9 kPa for apparel-weight use, 12 kPa for heavier duty

Decision 4

Abradant: standard wool, changed at the interval the method sets

Decision 5

Specimen: the production construction, with gauge and yarn count stated, tested in both directions

Decision 6

Acceptance figure: a cycle count plus a rating, never a cycle count alone

Step One: Decide Whether Abrasion Governs at All

Before commissioning anything, ask what the returns desk actually sees. If complaints are about handles pulling away, a seam opening, or a colour transferring onto a shirt, abrasion is not the governing risk and testing it first is spending the test allowance on the wrong row of the matrix.

Abrasion governs where the bag meets a repeated rubbing surface: a base set down on pavement, a body carried against a coat seam, a strap against a shoulder. It sits alongside tensile strength to ISO 13934-1 or ASTM D5034, seam strength to ISO 13935-2, and colour fastness to the ISO 105 series, and none of those four substitutes for another.

For a first programme, run all four on five pieces per colourway. The cost is modest relative to a season, and the result tells a buyer which row actually governs for this construction, so subsequent seasons can test one row instead of four and still be defensible.

There is a second reason to run the full set once: it converts an argument into a measurement. A dispute about whether a bag failed because the surface wore or because the join gave way is settled in one afternoon by two reports, and settled in a way that survives a retailer's question rather than resting on whoever spoke most confidently in the meeting.

Step Two: Choose the End Point

ISO 12947 is published in parts and each part measures a different thing. Part 2 determines specimen breakdown, the point at which a stated number of threads or loops have broken. Part 3 determines mass loss. Part 4 assesses appearance change, covering fuzzing, pilling and colour change.

For a bag, Part 2 and Part 4 are the two that matter and the choice between them is commercial. Breakdown answers how long until the panel holes through. Appearance change answers how long until the panel looks tired, and for a branded bag that threshold usually arrives first.

Where the two are close, specify both and accept whichever binds first. Where a buyer can only fund one, appearance change is the better single choice for a knitted body and breakdown is the better single choice for a base panel, because those are the ways those two surfaces actually get returned.

Step Three: Choose the Pressure

ISO 12947-2 works at two nominal pressures, 9 kPa for apparel-weight end uses and 12 kPa for heavier duty. The same fabric produces a materially lower cycle count at the higher pressure, so the pressure is not a detail and a report without it is not comparable with another report.

For bag fabric the split is usually by panel rather than by style. A body panel rubbing a coat is reasonably modelled at 9 kPa. A base panel meeting pavement, or any panel on a work or travel bag, is better modelled at 12 kPa, and stating two pressures on one submission form is normal and adds no lead time.

One caution: because the two pressures give different counts, changing pressure between seasons silently invalidates the trend line. Where a buyer tracks abrasion results across programmes, fix the pressure in the specification and do not move it.

Step Four: Choose the Abradant and the Change Interval

The standard abradant is a specified wool fabric, and it wears. The method sets the interval at which it must be changed, and a laboratory that runs past that interval produces results that drift progressively lower across the specimens in a batch. This is a common and entirely avoidable source of a suspicious spread.

Ask the laboratory to state the abradant and the change interval on the report. It is one line, it costs nothing, and it is the fastest way to tell a genuine fabric inconsistency from a method artefact when a spread looks odd.

Where a bag has a specific adversary, such as a coated base against concrete, a project-specific abradant can sometimes be agreed. That is a deviation from the standard and must be recorded as one, because a result obtained against a non-standard abradant is not comparable with any published figure.

Step Five: Choose the Specimen and the Direction

Test the construction that ships, not a representative swatch. State the gauge, the yarn count and the finished grammage on the submission form, and require the report to repeat them. A body knitted at E12 from a 300D yarn and a base knitted at E7 from a 600D yarn are two fabrics needing two submissions.

A knitted panel has a course direction and a wale direction, and they do not abrade alike. Where the method allows directional testing, test both and require both on the report. A single figure is usually the better of the two, and a buyer who does not ask for both will not know which one was reported.

Specimen count matters as much as direction. Five specimens gives enough information to see a spread; one gives a number with no context. Where the test allowance genuinely allows only one, record that the figure is indicative rather than a specification limit, so it is not reused as one next season.

Step Six: Choose the Acceptance Figure

An acceptance figure for a bag fabric has two components: a cycle count and a rating. For breakdown the cycle count is the result. For appearance change the rating is the result and the cycle count is the point at which it was assessed, so a specification needs both: 20,000 cycles with a pilling rating of at least 4, for example.

Pilling is rated on a 1 to 5 scale under the ISO 12945 series, where 5 is no change and 1 is severe pilling. Appearance change and colour change are assessed against grey scales running 1 to 5, where 5 is no change. A buyer who writes a cycle count but no rating has left the more informative half of the result unspecified.

Calibrate the figure against something already owned. Test a bag the buyer sells successfully and set the new target at or above that result, rather than against a published table, because end-use severity varies far more between ranges than any generic table can capture.

Where a Martindale Result Breaks Down on a Knit

A Martindale machine rubs flat, and a knitted surface is not flat. The loop stands proud of the plane, so abrasion concentrates on the crown of the loop first, which is why knit fuzzing appears so much earlier than knit breakdown and why a breakdown-only figure systematically overstates the serviceable life of a knit body.

The second issue is that a knit moves. Under the multidirectional Lissajous rub the loop can distort and shift, so the abraded area is not identical to the specimen area and edge effects appear sooner than they do on a woven fabric of similar mass. This is normal and is not a laboratory error, but it means knit results should not be compared with woven results.

The third is coated and laminated constructions. ISO 12947-2 excludes them and directs coated-surface abrasion to the ISO 5470 series. A coated knit needs the second method, and a buyer who asks for more Martindale cycles instead is asking for a number outside the scope of the method.

Turning the Six Decisions into One Specification Line

The six decisions compress into one clause with seven fields: method and part, pressure, abradant, end point, minimum cycle count, minimum rating, and the tested construction with its gauge and yarn count. Written once, it can be reused across colourways and seasons with only the construction line changing.

Add the reference sample clause and the clause is complete. Requiring the laboratory to test the same construction as the approved reference, and naming that reference on the report, closes the last route by which a strong number on a different fabric can satisfy a written requirement.

Frequently Asked Questions

People Also Ask