Performance fabrics: the claim has to survive a test report

The situation

Outdoor clothing is sold on claims printed on a swing tag. Every one of those claims has to be backed by a laboratory report that says the same thing. This lesson explains what the two headline numbers measure. A breathability figure quoted without its test method is not evidence, because one cloth can honestly carry four different numbers. And the layer that usually fails is not the waterproof one. It is a thin repellent finish on the outside.

6 November, 11:20. The lab report for PO NS-3308 arrives by email while 1,900 of the 3,400 jackets are already sewn.

The buyer is Nordvik Sport, Trondheim. Style SJ-42 is a men's three-layer softshell. FOB USD 31.80, order value USD 108,120. The hangtag artwork — approved, printed, sitting in the carton store — says 10,000 mm / 10,000 g/m2/24h, waterproof, seam sealed.

The report says three things:

1. Hydrostatic head, ISO 811 — how tall a column of water the fabric holds: 11,400 mm as received, 8,200 mm after 20 home washes.
2. Moisture vapour transmission, JIS L1099 B-1 — how much sweat vapour can escape: 9,100 g/m2/24h.
3. Water-repellency spray test, AATCC 22 — how well the outer face sheds water: 90 as received, 70 after 5 home washes.

The buyer's specification requires a spray rating of at least 80 after 5 washes, and at least 70 after 20. The jacket fails on the third line — and only the third line. The membrane is fine. The seams are fine. The finish that sits on the outside of the face fabric is not.

Water-resistant, waterproof, and the finish everyone confuses with both

A performance jacket carries two entirely different things. They are made by different suppliers, at different points in the chain.

A membrane or coating is a layer bonded to the face fabric. It is what stops liquid water. It is measured in millimetres of water column: how tall a column of water the fabric holds before the third drop appears on the other side.

A DWR — durable water repellent — is a finish padded or sprayed onto the face fabric's outer surface. It stops the face fabric wetting out, meaning soaking up water. It is not waterproofing, and it never was.

The consequence is the single most misunderstood thing in technical outerwear. When the DWR is gone, no water passes the membrane. The jacket is still, technically, exactly as waterproof as the day it was made. But the face fabric soaks. The soaked layer blocks vapour from escaping. The wearer's sweat condenses on the inside of the membrane. The wearer arrives wet, and reports that the jacket leaks. It did not leak. It stopped breathing, because breathability depends on a dry face.

The pressure points matter more than the rain. A rucksack strap, a knee on wet ground and a seated backside all press water against the fabric far harder than falling rain does. That is why a number that looks generous for a shower is the number that fails under a strap.

The breathability number is meaningless without its method

This is where merchandisers get beaten in a negotiation. So it is worth being exact.

MVTR — moisture vapour transmission rate, in grams per square metre per 24 hours — is not one test. It is at least four, and they do not produce comparable numbers on the same fabric. The laminate in SJ-42 was tested four ways by the same lab:

A supplier quoting 21,000 and a supplier quoting 4,600 may be selling you the identical laminate. Whenever a breathability figure appears without a method beside it, it is not data.

RET is the honest one, because it measures resistance rather than throughput. Under 6 is extremely breathable. 6 to 13 is very breathable. 13 to 20 is breathable. Above 20 is not breathable in any useful sense. The value on our laminate is 9.

Seam sealing is where a waterproof jacket usually leaks

An 80/12 needle leaves a hole around 0.7 mm across, and SJ-42 has about 11.4 metres of seam that has to be waterproof. A laminate holding 11,400 mm of water column with unsealed seams is a jacket with several thousand holes in it.

Sealing means a tape bonded over the stitch line with hot air at 420 to 480 degrees Celsius, running at 3.5 to 4.5 metres a minute. The tape is usually 20 mm wide for straight seams, and 13 mm for curved and complex ones. It is a separate operation, with its own machine and its own trained operator. It is not fast.

A taped seam has its own tests to pass:

• Hydrostatic head across the taped seam — typically at least 5,000 mm, and typically retested after 20 washes.
• Peel strength of at least 8 N per 25 mm, so the tape does not lift at the edge.
• A visual check that no tunnel or channel remains under the tape at a seam intersection. That is where nearly every real leak starts.

Costed, on SJ-42: 11.4 metres of sealed seam at USD 0.11 a metre is USD 1.25 a jacket, or USD 4,250 on the order. That is 3.9 percent of the FOB — for an operation many cost sheets forget entirely, until the sample comes back with a wet lining.

Wicking is a construction, or it is a finish that washes away

On the knit side of performance, the claim is moisture management rather than waterproofing, and it is tested differently. One test is vertical wicking height in millimetres after a set time. The other is AATCC 195, the moisture management test, which grades the way liquid spreads and moves through the two faces of the fabric.

Hold on to the same distinction as with DWR: a hydrophilic finish is a chemical on the yarn, and it leaves. A wicking construction does not leave, because it is geometry rather than chemistry — a channelled or profiled polyester filament, a double-knit with a water-hating inner face and a water-loving outer face, a capillary difference between the two layers. Ask which one you have been sold. And ask for the test after 20 washes, not as received.

What the failure cost, in dollars

Back to the report. The DWR is C0 — a fluorine-free chemistry the industry moved to as C8 was withdrawn and C6 restricted. C0 repels water well and oil badly, and it depends more on heat reactivation than the fluorinated finishes it replaced.

Three options were costed on the day the report landed.

The price reduction in option 2 is 6 percent of FOB — USD 1.91 a jacket on USD 31.80, across 3,400 jackets. The air freight in option 3 is 3,400 jackets at 0.62 kg each: 2,108 kg at USD 5.40 a kilo.

The factory took option 1 and asked the buyer for a four-day extension. The buyer granted it, because the jackets were physically in the building and the re-treatment was visibly booked. Total damage: USD 3,710 and nine days. Against a possible USD 11,383.20 for the same outcome shipped on time, and USD 7,242 for giving the claim up.

Act as a technical outerwear quality manager. I need to know whether the claims we are about to print can be defended. Style facts: buyer [BUYER], PO [NUMBER], style [STYLE], quantity [QTY] pcs, FOB USD [FOB], construction [2-LAYER / 2.5-LAYER / 3-LAYER / SOFTSHELL], face fabric [DESCRIBE], membrane or coating [DESCRIBE], DWR chemistry [C6 / C0 / OTHER]. The hangtag and the marketing copy say: [PASTE EVERY CLAIM WORD FOR WORD]. The test reports say: [PASTE EACH RESULT WITH ITS METHOD AND WHETHER IT WAS AS RECEIVED OR AFTER WASHES]. Do the following. First, take each claim in turn and tell me which specific test result supports it, or state plainly that nothing in the reports supports it. Second, for every breathability figure, name the method and tell me what the same fabric would read on the other common methods, so I know whether we are comparing like with like. Third, check the durability side: which results are as received only, and what the buyer's specification requires after washes. Fourth, tell me whether the seams are covered — taped seam hydrostatic head, peel strength, and whether they were retested after washes. Fifth, where a claim is not supported, give me the options in order of cost: reword the claim, re-treat the goods, or retest, and say what each is likely to cost and how long it takes. Be conservative: if a claim cannot be evidenced from a report in front of you, treat it as unsupported rather than probable.