A returned mosquito net almost never has a hole in the middle of a panel. It has a split along a seam, a tear where a corner was pulled, or a line of perforations where the stitching ran. The fabric was not the weak point. The join was. And because the join is invisible in a photograph and unglamorous in a brochure, it is the first place cost gets taken out.
Looking in the wrong place
Buyers evaluate netting the way they evaluate woven fabric: they look at the sheet. Mesh regularity, hand feel, weight, colour. All of that is about the cloth. None of it predicts whether the product will hold together.
The reason is geometric. A 156-mesh fabric has roughly 80 percent open area. The material is a lattice of thin members with large gaps between them. In a densely woven fabric, a sewing needle slides between warp and weft yarns, pushing them aside. In an open mesh there is nothing to push against — the needle either passes through a hole or it pierces a filament.
Which one happens depends on the ratio of needle diameter to aperture, the yarn's ability to deflect, and the stitch density. Change any of those and the damage rate changes. This is why two factories can produce identical cloth and deliver products with very different service lives.
Why the needle is the problem
Three distinct damage mechanisms operate at the stitch line:
Filament severing. The needle cuts some filaments in the yarn it passes through. At 75D with 36 filaments, losing a few is survivable — the remaining filaments carry the load. At 50D the same needle removes a larger fraction of the cross-section, and the yarn at that stitch is permanently weakened.
Perforation lines. Stitches spaced closely together create a line of holes that act as a pre-cut tear path. Under load, the fabric does not tear across the seam — it tears along it, following the perforations. This is the most common failure geometry in cheap netting and it looks like the seam “unzipped.”
Stress concentration. The seam is a stiffness discontinuity. The stitched line is far less extensible than the open mesh around it, so when the panel is loaded, strain concentrates at the boundary between stitched and unstitched material. The first stitch at each end of a seam carries a disproportionate share.
Reference specifications respond to this by requiring bursting strength for net and seams as a single figure. That phrasing is deliberate. A flat-goods number that the seam cannot match describes a fabric, not a product.
The four seam decisions
| Construction | How it works | Weakness | Where it belongs |
|---|---|---|---|
| Overlock (3 or 4 thread) | Wraps the edge with looping threads and trims it | Trims the edge, cutting yarns; dense needle line creates perforations | Low-cost volume products, non-structural joins |
| Flatlock / coverstitch | Joins two panels flat with no raised ridge | Needs more handling time; machine setup is fussier | General-purpose netting where the seam will be loaded |
| French seam | Encases raw edges inside a folded seam, sewn twice | Slow, adds bulk, doubles thread consumption | Premium products, exposed seams, skin contact |
| Bound edge | Wraps the join in a woven tape or binding | Costs material and labour; adds weight | Load-bearing corners, attachment points, tie-outs |
Beyond the seam type, three parameters decide the outcome:
Stitch density. Ten to fourteen stitches per inch is the working range for fine netting. Below ten, the stitch length is long enough that individual stitches can be snagged and pulled. Above fourteen, the needle holes begin to merge into a continuous perforation line and the seam becomes a tear guide. More stitches is not more strength.
Thread choice. The thread should match the fabric's fibre and, critically, its shrinkage. A cotton-wrapped thread on polyester netting shrinks differently after the first wash, puckering the seam and loading the stitches unevenly. Bonded polyester thread in a tex size matched to the fabric weight is the standard answer.
Needle size and point. A smaller needle removes less material. Ball-point needles, designed to deflect around yarns in knits, help on multifilament mesh but do less on very open structures where there is nothing to deflect against. This is one of the few places where a factory's experience shows up as a measurable difference in returns.
Diagnosing a seam by how it fails
The failure mode tells you which decision was wrong, which is useful when you are evaluating a sample or a return:
| What you see | What it means | What to change |
|---|---|---|
| Fabric tears beside the stitch line; thread intact | The seam is stronger than the cloth. This is the good outcome | Nothing. The construction is working as designed |
| Thread breaks, fabric intact | Thread is too weak or has degraded in UV | Heavier or UV-stabilised thread |
| Fabric splits along a line of holes | Perforation line from excessive stitch density or oversized needle | Reduce stitches per inch; smaller needle |
| Seam opens at one end and runs | No back-tack or bar-tack at the terminus; load concentrated on the first stitch | Reinforce seam ends; bound corners |
| Seam puckers and pulls after washing | Thread shrinkage mismatched to fabric | Match thread fibre and shrinkage to the netting |
Note the first row carefully. A good seam is designed so that the fabric fails before the seam does, because fabric failure is local and seam failure is catastrophic. If you pull a sample apart and the stitch line opens first, the product has its priorities inverted.
What to put in the specification
Most netting purchase orders specify the fabric and say nothing about the join. That is where the money is lost. A workable specification clause:
- Seam type named explicitly — flatlock, French, or bound, not “sewn.”
- Stitch density stated as a range, for example 10–14 stitches per inch.
- Thread specified by fibre and size, with shrinkage matched to the netting.
- Bursting strength for net and seams at the same minimum, per the reference figure for the yarn weight.
- Reinforcement at corners, tie-outs and any point where a load is applied, by method not by intention.
Five lines. They cost nothing to write and they close the gap between a fabric sample and a finished product that survives its second season.
What this means when you buy
Two minutes of physical testing on a sample will tell you more than any specification sheet:
- Pull a seam apart. Grip either side and pull until something gives. Fabric tear beside the stitch line is correct. Thread break or a run along the perforations is not.
- Count the stitches. Hold a ruler against the seam. Fewer than ten per inch means long stitches that snag; more than fourteen means the seam is a tear guide.
- Look at the seam ends. The first and last stitch of every seam carries the highest load. If there is no back-tack or bar-tack visible, the seam will open there.
- Wash one sample. A single warm wash reveals thread shrinkage mismatch as puckering along the stitch line. This is the failure that appears in the customer's hands, not in inspection.
If a quotation is materially cheaper than others at the same fabric weight, the seam is usually where the difference was taken — shorter stitch runs, overlocked instead of flatlocked, lighter thread. Ask what seam type is used before asking for a discount.