Burst Factor vs Ring Crush Test
Burst factor (BF) and ring crush test (RCT) values both describe paper strength—but they stress the sheet differently. Corrugated buyers who understand both tests make fewer mismatches between mill certificates and corrugator reality.
Burst factor in brief
Burst testing applies hydraulic pressure until the sheet ruptures. BF relates burst strength to grammage so papers at different GSM can be compared more fairly. BF is ubiquitous on Indian packaging mill certificates and buyer POs.
Deep dive: what is BF in craft paper.
Ring crush test (RCT) in brief
Ring crush measures compressive strength of a narrow strip formed into a ring—relevant to how liner and medium resist crushing forces in the flute structure. RCT is especially discussed for liner grades in some export specifications.
When BF is the primary gate
BF is often the first filter for medium and general-purpose liner grades in domestic corrugated programmes. It correlates with perceived “toughness” and is easy to specify on orders.
When RCT gains weight
Some brand owners and structural specs emphasise RCT on liner for stacking-intensive lanes. If your customer sheet lists RCT minima, request mill data alongside BF—not all grades are optimised identically for both.
Comparing mills fairly
Align:
- Test standard and sample conditioning (moisture, temperature)
- Same GSM and shade lot
- Whether values are minimum guarantees or typical averages
On the corrugator
Lab tests do not replace finished box compression and drop testing. Moisture, flute crush, and joint quality can dominate field performance. Store reels properly; see moisture and storage.
Nexa Papers specification practice
We manufacture craft paper BF 12–20, GSM 90–180, natural and golden shades. Share your full test requirement list when enquiring so operations can confirm fit.
Conclusion
Use BF and RCT as complementary indicators, not competitors. Specify what your box must survive in transit, then choose paper tests that best predict that outcome—and validate on your line.