What is BF in Craft Paper?
Burst factor (BF) is one of the first numbers corrugated buyers check on a mill certificate—and for good reason. It indicates how much hydraulic pressure the paper can withstand before rupture, which correlates with box strength when combined with the right GSM and flute profile.
What burst factor measures
Burst factor is derived from the burst strength test (commonly Mullen burst in many markets). The test applies increasing pressure to a clamped sample until the sheet fails. BF normalises burst strength relative to basis weight so you can compare papers of different GSM on a more level basis.
On Indian mill test reports you will often see BF listed alongside GSM, moisture, and sometimes ring crush (RCT). Treat BF as one variable in a system—not the only measure of “good paper.”
Why BF matters for corrugated buyers
Higher BF generally supports stronger board combinations: you may achieve target compression strength at a lower GSM, or improve stacking performance for warehouse and export lanes. Conversely, overspecifying BF adds fibre cost without benefit if your box design already exceeds customer requirements.
Common pitfalls include:
- Specifying high BF on medium only, while liner grade is too light for the load
- Ignoring moisture content at the corrugator (wet paper behaves weaker than lab-tested reels)
- Comparing BF across mills without aligning GSM, shade, and test method
Typical BF ranges in packaging programmes
Programme buyers for agri-produce, tiles, beverages, and general industrial cartons often work in roughly these bands (confirm with your structural designer):
- 12–14 BF: lighter mediums, cost-sensitive inner packs, some single-wall applications
- 14–16 BF: workhorse grades for medium and lighter liners
- 16–18 BF: heavier mediums, export lanes, higher stacking
- 18–20 BF: demanding combinations where mill and converter discipline must be high
Nexa Papers manufactures craft paper from 12 BF to 20 BF within 90–180 GSM, in natural and golden shades, from Morbi.
BF and GSM work together
Two sheets with the same BF but different GSM will not perform identically on the corrugator or in the finished box. When trialling a new supplier, run parallel tests at your target GSM rather than accepting BF alone from a certificate.
For guidance on basis weight selection, read choosing GSM for corrugated applications. For how BF relates to ring crush, see burst factor vs ring crush test.
How we confirm BF at Nexa Papers
Quality records are maintained per production run. Before placing a programme order, share your:
- Target BF band and acceptable tolerance
- GSM and shade (natural or golden)
- Flute type (A, B, C, E, etc.) and whether the grade is medium or liner
Our operations team will confirm available grades and suggest trial reel sizes. Call operations or use the contact page for specification sheets.
Conclusion
BF is a practical shorthand for paper toughness, but successful packaging programmes balance BF, GSM, moisture control, and board design. Use BF to shortlist grades, then validate on your corrugator with real loads and transit conditions.