Density is the figure that gets written into a purchase order and then measured by nobody. This is what it controls, how to measure it, and what happens when it drifts.
What density actually controls in cotton/T.C
The real weight and durability driver, and the number suppliers omit.
That makes it a design decision rather than a purchasing one, which is why changing it after the product is fixed costs more than changing the material.
For Cotton and T/C fabric, the working range is 88×56 to 133×72 threads/inch. Inside that band the choice is commercial; outside it, the product changes category and so does the price.
What 88×56 to 133×72 threads/inch does not tell you
| Position | Value | Effect on cotton/T.C | Where it shows up |
|---|---|---|---|
| Floor | 88×56 to 133×72 threads/inch | Lowest cost, least margin for process variation | Pilling on blends within a season |
| Working middle | 88×56 to 133×72 threads/inch | Predictable performance at a normal price | Nothing to negotiate, nothing to explain |
| Ceiling | 88×56 to 133×72 threads/inch | Best performance, highest cost | Cost the end product may not recover |
Specifying the ceiling is only justified when the end product carries a warranty that would be expensive to honour. Otherwise it is cost without a customer-visible benefit.
The figure that decides the outcome is not density itself but the tolerance around it. A supplier who quotes 88×56 to 133×72 threads/inch without a tolerance has not quoted a specification, and the first lot will define the tolerance for you.
How to measure density
The reference method here is Colour fastness to washing, run to ISO 105-C06, with an acceptance of >= grade 4. The method is the easy part; sampling and conditioning are where reports diverge.
Take samples from the beginning, middle and end of the run. A single sample from the top of a roll tells you about the top of that roll, and density varies more across a run than most buyers expect.
Record the measured value rather than pass or fail. A marginal pass on density tells you the process is running at the edge, which is the information you need before the next lot rather than after it.
Density does not stand alone
Density moves with weight (100-250 gsm) and with shrinkage (<= 3 % pre-shrunk, <= 6 % raw). Tightening one usually costs money in another, and a supplier who accepts every tolerance without comment has either not understood the interaction or is planning to substitute.
When you change density, re-check the two neighbours before you approve the sample. Most of the samples we re-make are caused by a change in one figure that was not followed through.
The clause to write for density
The line below is the version we can quote against without inventing anything. Density appears with a tolerance and a test, not as a standalone number.
65/35 polyester/cotton twill, 21s x 21s, 108×58, 240 gsm, 160 cm, sanforised shrinkage <= 3 % after 3 industrial washes, colour fastness to washing >= grade 4, Pantone 19-4127 TCX
A specification without a test method is a preference. It becomes a requirement when the method and the acceptance value are both named, because then a substitution is visible.
When density goes wrong
Pilling on blends. Surface fuzz and balls at cuffs and collars.
The cause is usually short staple and a high polyester content that migrates to the surface.
The test that catches it: ISO 12945-2 at 2000 and 7000 rubs.
What to specify instead: Longer staple, lower polyester ratio, or a singed and bio-polished finish.
The pattern is consistent: the failure appears months after delivery, is hard to attribute, and the cost lands on the buyer. That is the argument for measuring density on every lot rather than on the development sample.
Four questions about density, before you order
- What tolerance do you hold on density, and what did your last three lots measure against it?
- Which method do you use for colour fastness to washing, and which laboratory signs the report?
- When density falls outside 88×56 to 133×72 threads/inch, do you rework, downgrade, or ship and hope?
- Which of weight or shrinkage would you move first to hit a lower price?
The answers are more useful than a certificate, because they show whether the process is controlled or merely inspected. Full ranges for cotton/T.C are on the product page, and the measurement regime is described on the quality control page.
Questions buyers ask before ordering
Do you offer FR finish?
We can arrange it through a partner finisher, with certification. It changes hand and strength, so we sample before quoting.
Do you supply 3-cycle shrinkage figures?
Yes, and we recommend insisting on them. A 1-cycle figure hides progressive shrinkage, which is what ruins uniforms.
From quotation to specification in seven lines
Leave the tolerance and the method out and every dispute is settled by whoever needs the goods more.
- Composition: the figure you will accept inside the 100 % cotton / 65-35 / 80-20 T/C band, the tolerance on it, and the method used to measure it.
- Yarn count (16s / 20s / 21s / 32s / 40s): name the number, not the word. If the answer only repeats the band, ask which point inside it is being offered for this order.
- Construction: 1/1 plain / 2/1 twill / ripstop is the market band. Fix the figure you will test at goods-in, and the instrument you will test it with.
- Density (88×56 to 133×72 threads/inch): fix the value per shipment, and state who pays for the re-test if a lot lands outside it.
- Sample retention: one production sample per lot stays with the mill for twelve months. Claims are settled against it, not against memory.
- Test reports: name the standard as well as the test. A pass on a development sample is not a pass on a production lot.
- Deviation rule: anything outside the agreed bands is reported before shipment, not after arrival.
Questions worth asking before the price is agreed
The questions below are the ones that cannot be answered from a catalogue, which is exactly why they are worth asking.
| Question | Answer that should worry you | Answer that holds up |
|---|---|---|
| Who signs the test report, and against which standard? | “Our QC department signs it.” | A named standard, a named method and a signature that belongs to somebody who can be asked again next year. |
| How do you hold yarn count inside 16s / 20s / 21s / 32s / 40s? | “That is standard for us, no problem.” | The last three lots’ readings, the instrument used and who signs the report. Shade variation between lots starts here. |
| What happens if density misses the 88×56 to 133×72 threads/inch requirement? | “It will not happen.” | A re-test clause, the tolerance on the re-test, and the point at which the lot is remade rather than discounted. |
Need density specified and tested against your end use?
Send the end use, the quantity and the destination market, and we will come back with a specification that meets it, a price at your volume and the test reports that back it up. Samples are free for qualified programmes; we charge the courier only.
Related reading
Sample cut with your values on it · Neutral packing and private label · Consolidation, documents and lead times
