Bursting Strength of Corrugated Boxes Explained
Bursting strength, or BS, is the pressure a corrugated board can withstand before it ruptures, tested on a burst tester and usually reported in kg per square centimetre. It is the most common strength number on Indian box specifications. Higher BS means the board resists rough handling and point pressure better.
What the test actually does
A sample of board is clamped over a rubber diaphragm. Pressure rises underneath until the board gives way, and the reading at rupture is the bursting strength. It is a quick, repeatable check, which is why units run it batch by batch rather than once in a while.
What moves the number
| Factor | Effect on BS |
|---|---|
| Paper GSM | Heavier liners raise BS directly |
| Paper quality | Higher grade kraft raises BS at the same GSM |
| Ply count | More layers, higher BS |
| Moisture | Damp board tests lower, sometimes sharply |
| Glue application | Poor bonding weakens the sheet |
What to ask your supplier
- Which BS the quoted board is built to deliver for your spec.
- Whether BS is tested per batch and whether a report is available on request.
- How board is stored in monsoon months, since moisture quietly drags BS down.
BS is not the only number that matters. Stacking performance depends more on edge crush values, which is a separate test. But as a first filter for board quality, BS remains the most practical check a buyer can ask for.
Frequently asked questions
What unit is bursting strength measured in?
Commonly kg per square centimetre in India. Reports may also show it in kPa.
Is BS the same as box strength?
Not exactly. BS measures the board sheet. Whole-box performance also depends on flute, size, moisture and how the box is closed.
Why did the same box test differently in two seasons?
Moisture. Humid air lowers test values, which is why storage and conditioning matter.