Our slub jersey tees look different in bulk than the sample. What should the fabric spec say?
Slub is a deliberate irregularity, so "looks like the sample" is not enough. Fix the yarn, the fabric weight and a physical reference before bulk.
Our sample slub tee had soft, scattered slubs. The bulk tees have longer, heavier slubs in places and look almost striped on some pieces. The factory says slub is meant to be irregular. What should we have written down?
Main answer
Slub yarn is spun with intentional thick and thin places. Knitted into jersey, those thick places show as the slubs that give the fabric its textured look. The look depends on how long the slubs are, how thick they are compared with the base yarn, and how often they occur. Those settings come from the spinning program, so a different yarn lot, a different spinner or a changed program can give a visibly different fabric even when the yarn count on paper is the same. The factory is right that slub is irregular, but the type of irregularity can and should be specified.
Fix the yarn, not only the fabric
Ask the mill to name the slub yarn: base count, fibre, spinner and slub program or reference. Ask for the same yarn lot to be used across the order where possible, and for notice before any change. If the mill cannot hold the yarn, ask it to knit a new swatch for approval before bulk knitting, not after.
Specify the fabric around it
Give the construction, fibre content, target weight with a tolerance measured by a named method such as ASTM D3776, and width. A slub fabric knitted tighter or looser than the sample changes how the slubs sit on the surface. Add shrinkage limits after a named wash procedure such as ISO 6330, since slub jersey can relax differently from plain jersey.
Use a physical reference
Words cannot fully describe a slub effect. Keep a signed, dated swatch of the approved fabric, large enough to show the pattern repeat, with a copy held by the factory and the mill. Approve a bulk fabric header against it before cutting. Look at it at arm's length as well as close up, because striping or banding is easier to see from a distance.
Watch for striping
If slubs line up across the width, the fabric can look striped. This can come from the yarn program or from how yarn packages were mixed on the knitting machine. Agree with the mill that visible horizontal banding is a defect unless it matches the approved reference.
Check surface wear
Thick slub places can pill or fuzz more than the base yarn. Test pilling with a named method such as ASTM D3512 on washed fabric, and set a minimum rating with the mill.
Sources and further reading
- ASTM D3776/D3776M — Mass per Unit Area (Weight) of Fabric
- ISO 6330:2021 — Domestic washing and drying procedures for textile testing
- ASTM D3512/D3512M — Pilling Resistance: Random Tumble Pilling Tester
Standards and rules are summarised from their published scope or official guidance. Use the current edition and confirm requirements for your market.
Three perspectives on this question
Purchasing perspective
I'd put the slub yarn reference and a no-change clause in the fabric order, and require a new swatch approval if the mill has to change spinner.
Merchandising perspective
The slub look is often the reason a customer picks the tee. I'd judge the bulk header on a body form in normal light before signing off.
QC perspective
We'd lay several bulk pieces side by side at inspection and look for banding from a few metres away, comparing against the signed swatch.
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