Kraft Paper Manufacturing Process
From wood or recycled fibre to finished reel, kraft and craft paper production is a continuous balance of fibre quality, refining, machine settings, and drying energy. Understanding the process helps buyers interpret mill certificates and set realistic specifications.
Pulping and fibre preparation
The kraft (sulfate) process cooks chips or prepared recycled furnish to separate fibres from lignin. Virgin pulping targets long, strong fibres; recycled lines add cleaning, screening, and de-inking stages depending on source quality.
Fibre mix directly affects burst factor, tear, and how the sheet runs on the corrugator. Mills with disciplined quality gates reject furnish that would destabilise BF/GSM targets.
Stock preparation and refining
Before the paper machine, pulp is refined to develop fibre bonding and target freeness. Refining energy influences strength versus drainage speed—too aggressive refining can hurt machine runnability; too little can leave the sheet weak at a given GSM.
Forming and wet press
On the wire or forming section, fibre mats into a continuous sheet. Consistency here drives GSM uniformity across reel width—critical for corrugators that run at high speed.
The wet press removes water mechanically before the drying section, improving energy efficiency and sheet density.
Drying, sizing, and winding
Multi-cylinder drying (as in many Indian packaging mills) evaporates remaining moisture to target levels. Exit moisture that is too high risks reel damage and weak corrugating; too low can make the sheet brittle.
Surface sizing or starch application may be used where printability or surface strength is required. Finished paper is wound into jumbo reels, then slit to customer width.
Our Morbi facility is configured for high-volume craft paper output—see facility for capacity and operations context.
Quality control and release
Typical release tests for packaging grades include GSM, moisture, burst (BF), and sometimes ring crush or tensile. Certificates should map to the grade name on your purchase order.
When auditing a new mill, ask about:
- Frequency of online GSM and moisture checks
- How out-of-spec reels are quarantined
- Traceability from reel number to production shift
What buyers should specify upstream
Clear orders reduce mismatch at dispatch:
- Shade (natural / golden), BF band, GSM
- Reel width, diameter, and core size
- Acceptable moisture range at receipt
- Whether certificates must accompany each lot
Nexa Papers produces 150 MT/day of craft paper in Morbi within BF 12–20 and GSM 90–180.
Conclusion
Manufacturing discipline—not marketing claims—determines whether paper repeats from reel to reel. Visit or correspond with your mill early, align on test methods, and trial before programme volumes commit.