In "cotton poplin 40x40", poplin is the weave and 40x40 is the yarn count in the warp and the weft. Both directions use a 40s cotton yarn, which is a fine yarn. In "cotton twill 2/1", the numbers describe how the threads interlace, not how fine the yarn is.
Mills in Gujarat and elsewhere in India speak in this shorthand all the time. If you copy it into an enquiry without knowing what is missing, you will get quotes for different fabrics and not realise it.
What is poplin fabric?
Poplin is a plain weave: each weft thread goes over one warp thread and under the next. What makes it poplin is the density. There are more warp threads per inch than weft threads, so the fabric shows a very fine rib across its width. It feels smooth, crisp and light, which is why it is used for shirts, blouses and light dresses.
The background to the weave family is in poplin, oxford, twill and dobby: how shirting fabrics differ. This article goes one step further and shows how the notation is built.
How do you read 40x40?
The first number is the warp count and the second is the weft count. These are usually English cotton counts, written Ne. A higher number means a finer yarn, so 40s is finer than 30s and coarser than 60s. If the count is for a blend or a different system, such as denier for a filament, the spec should say so.
A full poplin spec normally has a second pair of numbers after the counts, for example 40x40 / 133x72. This is the thread density: warp ends per inch by weft picks per inch. The counts say how fine the yarn is. The density says how tightly it is packed. Our guide to thread count, EPI and PPI explains why the density matters more to hand-feel than the count alone.
If you only send 40x40, a mill can offer a loose, light fabric or a dense, heavy one and both match your words. Always add the density, or the finished weight in grams per square metre.
What does twill 2/1 mean?
In a twill, the weave steps one thread sideways on each row, which creates the diagonal line you can see on the face. The 2/1 describes the repeat. The warp thread passes over two weft threads and then under one. A 3/1 twill passes over three and under one, and gives a stronger diagonal and a more warp-faced look.
A 2/1 twill is a standard choice for chinos, work trousers and shirts. It drapes better than plain weave, hides marks better and is usually a little heavier and more hard-wearing for the same yarn count.
Two more details are often left out. The first is direction: a right-hand twill and a left-hand twill look different on the same fabric. The second is which face is the right side. If your product depends on the diagonal direction, say so.
What a complete fabric line looks like
A mill can quote accurately only if the line contains every item below. These are the parts we ask buyers to confirm before we send an enquiry:
- Fibre and blend, such as 100% cotton, or cotton with a percentage of polyester or elastane.
- Weave: plain (poplin) or twill 2/1, 3/1, with direction if it matters.
- Warp and weft counts, such as 40x40, and whether they are combed or carded.
- Thread density in ends and picks per inch, or the target weight in grams per square metre.
- Finished width, measured between the selvedges, and the finish: peach, mercerised, easy-care or none.
- Dyeing method and shade, plus the colourfastness and shrinkage limits you will test against.
Putting it into a spec
The easiest way to avoid confusion is to write the spec once in a fixed format and use it for every supplier. How to write a fabric specification for an Indian mill gives a template, and it is worth sending a physical swatch with it. The swatch settles any argument about what "40x40" was meant to look like.
Also keep in mind that the same numbers on paper can still produce a different fabric. Yarn quality, finishing and the loom setting all affect the result, so approve a pre-production sample against your own tests before you confirm the order.
Next step
If you are not sure how to translate a sample or a competitor's fabric into a spec a mill can quote against, we can do it with you. We find and audit manufacturers, check samples and have lots tested. Book a free sourcing review and bring the fabric with you.