Supply and commercial
Why does the second batch feel different from the first?
Nonwoven is made from fibre and air, so small batch variation is normal. The question is whether the difference is inside the specification you agreed, and whether that specification was written tightly enough.
At a glance
Specification at a glance
| Property | Normal batch variation | Becomes a defect when |
|---|---|---|
| Weight | ±1.5 to 3 g/m² | Outside the stated tolerance |
| Hand feel | Noticeable to touch | Changes the product feel at retail |
| Tensile | ±10 % typical | Below the minimum |
| Colour | Within Delta E tolerance | Visible side by side in one pack |
| Width | ±2 mm | Causes line stops |
What causes it
Fibre lot, humidity, line speed and bonding temperature all shift a little between runs. A supplier who reports the batch values lets the buyer see that variation before the goods ship.
When to tighten the specification
If the product is judged by hand or by shade, tighten those properties and accept the cost. If it is judged by strength, tighten tensile and let the hand move.
Send the specification question with the numbers
Width, weight, roll build or a claim to resolve: tell us what the line sees and we answer with the tolerance and the next step.
Questions
Common questions
Should batches be identical?
No, that is not physically achievable. They should be inside the agreed tolerance.
Can I ask for a specific batch?
For a trial yes. For production, the batch code is recorded so you can trace which one you received.
Does a premium grade vary less?
Usually, because more is spent on fibre consistency and line control. Ask for the batch data rather than the assurance.