Four-Point

Four-point — usually written four-point burst or 4-point burst — is a burst strength test. A circular fabric specimen is clamped over a rubber diaphragm and pressed against a rigid plate by an extending ring until the fabric bursts. The force needed is recorded, in Newtons (or kgf, depending on the standard).

There are two main burst methods and they are not interchangeable:

For a woven mill, ISO 1419 four-point is the relevant one. Mullen is the knit and nonwoven method. If a supplier quotes a burst figure without naming the method, it is not interpretable.

What it actually measures

Four-point burst tests the fabric, not the yarn. Because the load is applied as pressure over an area rather than as a pull along an axis, the result reflects the cloth's behaviour as a plane — how it distributes stress, whether yarns can mobilise together, and how the weave structure responds locally. That is why the same fabric can have a burst figure that does not track with its tensile strength: burst rewards a structure that shares load across yarns, tensile rewards one that resists a direct pull.

A woven construction will normally burst at a much higher force than a knit of the same weight, because a knit can open and distort under local pressure while a woven structure holds until yarns break. Burst is therefore a strong discriminator between constructions.

Where it is used

Four-point burst is specified less often than Martindale or tensile, but it matters in specific places:

• Medical and hygiene fabrics — drapes, gowns, scrubs, where a local puncture is a clinical failure
• Protective and barrier fabrics — where a localized breach is unacceptable
• Geotextile and industrial cloth — bags, filters, filtration components
• Coated and laminated cloth — to check the substrate survives finishing
• Bag and sack fabric — where local stress is concentrated

For ordinary apparel and upholstery, four-point is rarely the governing test. It is worth asking for when the end use involves localised loading rather than distributed wear — that is the situation burst models.

Reading the number

General considerations rather than a specification table, because the useful figure depends entirely on the construction:

The last two are why burst figures vary between suppliers more than tensile figures do: a test on unconditioned cloth straight off the loom will not match a laboratory report taken a week later.

What to ask a supplier

1. ISO 1419 or ASTM D3786? For woven fabric it should be ISO 1419.
2. Conditioned or as-received? Ask for the conditioning time and atmosphere.
3. Greige or finished? A finish changes the result, and the finish is what you buy.
4. Tested in warp or weft, or an average? Woven fabrics can differ by direction.
5. Was the specimen taken from the edge or the body of the roll? Edge specimens can pick up selvage effects.

Why this is a mill conversation

Burst strength is one of those figures that is very sensitive to how the cloth was made — yarn tension, loom condition, and the finishing route. A trading intermediary quoting a burst number has taken it from a supplier's datasheet for a fabric that may not be the fabric in your order. Asking the mill directly, against your own construction, is the only way the number means anything.

Weaverine does not publish a four-point burst figure on this page. The result belongs to a specific construction and a specific condition state, and a generic number would describe cloth nobody is buying. Request the test report against your specification, and check that it names ISO 1419 and states the conditioning.