Fabric testing and lab reports: what to request and how to read them

A specification that cannot be measured is not a specification but a wish. Writing good fabric or fast colour into a contract writes nothing enforceable. Laboratory testing is what turns those phrases into numbers, and makes acceptance or rejection a matter of measurement rather than opinion.

Weight testing

The simplest test and the most useful. A standard circle of fabric is cut and weighed on a precision scale, giving grams per square metre. It is applied at several points across the roll, because weight can vary within it. Specify the required weight with a permitted tolerance in the contract, because every ten grams short is a saving for the factory and a loss for you in the feel of the product.

Shrinkage testing

The garment is measured, then washed and dried according to the care instructions printed on its own label, then measured again. The difference is expressed as a percentage in length and width. Untreated cotton shrinks 3% to 5%. Specify pre-shrunk fabric and set the permitted figure after three washes rather than one, because shrinkage accumulates.

Colour fastness tests

• To washing: does the colour fade or bleed onto adjacent white fabric.
• To rubbing: does colour transfer when rubbed dry and wet. Critical on dark shades and denim.
• To perspiration: important for sportswear and hot markets.
• To light: important for anything displayed in a window or worn under strong sun.
• To saliva: mandatory on clothing for small children.

Results are given on a graded scale where a higher number is better. Specify a minimum acceptable grade in the contract rather than simply asking for the report.

Pilling testing

The fabric is mechanically rubbed for a set number of cycles then compared against a reference scale. This is the test that reveals whether the t-shirt will look old after a month. Carded fabric pills faster than combed, and polyester blends are more prone than pure cotton. If your product is for retail, this test is worth specifying.

Tensile and tear strength

Measures the resistance of fabric and seams to separating. More important in uniforms and workwear than in an ordinary tee, and essential where the garment faces repeated stress.

Chemical safety testing

Covers banned aromatic amines, formaldehyde, heavy metals and pH. Legally required in many markets and effectively mandatory for childrenswear. Usually requested within textile safety certification.

How to read a lab report

• Check the date: an old report does not cover a new production lot.
• Check the sample description: is it the same fabric at the same weight in the same colour? A report on white proves nothing about black.
• Check the applicant name: is the report in the name of the factory sewing your order?
• Read the standard used, not only the result, because a result without a standard means nothing.
• Check the issuer: a known independent laboratory rather than the factory's internal lab.

Who pays, and when?

Testing is an additional cost normally borne by the importer, sometimes shared by the factory on large orders. The right time to request it is at fabric approval, that is, before production begins, not after the goods arrive. Testing after arrival proves the problem rather than preventing it.

Frequently asked questions

Do I need all these tests? No. Choose what fits your product: weight, shrinkage and colour fastness as a minimum, adding pilling for retail and chemical safety for childrenswear.

How long do they take? Usually three to seven working days.

Is the factory's own report enough? As an initial signal yes, but the report you rely on in a dispute must come from an independent laboratory.

We arrange testing at the fabric approval stage and attach the reports to the order documents.