1. What is kraft paper?
Kraft paper is paper made by the kraft pulping process: a chemical method that converts wood (or non-wood fibre) into long-fibre pulp by cooking chips in a hot alkaline solution of sodium hydroxide (NaOH) and sodium sulfide (Na₂S) called white liquor. The cooking dissolves lignin and frees cellulose fibres while leaving most of their length intact, which is why kraft paper is stronger than paper made by mechanical or sulfite routes. See our chemical vs mechanical pulping comparison for the full strength and yield breakdown.
The word kraft is German for strength. The process was invented by Carl F. Dahl in Danzig in 1879 and commercialised at the first Swedish mill in 1890. The 1930s recovery boiler closed the chemical loop, and kraft pulping overtook the sulfite process during the 1940s. Today it accounts for roughly 80% of global chemical pulp output per FAO 2024 forestry statistics. For the wider wood pulping process covering all routes, see our chemical pulping pillar.
Quick answer: Kraft paper is strong, brown (or bleached white), long-fibre paper made by alkaline chemical pulping. Brown kraft is unbleached. White kraft is bleached. Both come from the same process. The kraft route is dominant because chemical recovery makes it nearly closed-loop. For the foundational difference between pulp and paper, see our pillar definition.
2. Kraft paper types, full taxonomy
Most online guides list 4–6 kraft grades. The actual product space is much wider. Below are the 16 commercially recognised kraft grades, split by bleach status:
Unbleached kraft (brown, natural fibre colour):
Bleached kraft (white, finishable):
GSM ranges are indicative; specific mill grades vary by basis weight, machine speed and finishing pass per TAPPI standards.
3. Industrial kraft paper, the high-strength tier
Industrial kraft paper is a heavyweight unbleached grade (typically 120–300 GSM) engineered for tear and burst resistance rather than visual presentation. It is the workhorse behind cement sacks, chemical multiwall bags, void-fill protection for shipped machinery, and corrugating medium for heavy-duty boxes. Per CEPI's 2025 industry statistics, industrial-grade kraft accounts for roughly 35% of European kraft tonnage, with packaging end-use driving demand growth of ~4% per year.
Three sub-classes of industrial kraft:
- MD-strong kraft: fibre orientation optimised for the machine direction; ideal for sack tube extrusion.
- High-porosity kraft: engineered for cement-sack air permeability so dust escapes during filling without bag rupture.
- Wet-strength kraft: additives like polyamide-epichlorohydrin (PAE) resin lift wet tensile to 25–35% of dry strength for outdoor/construction use.
If your application needs >200 GSM with burst strength above 6 kg/cm², you're looking at industrial kraft, not retail kraft.
4. How kraft paper is made, 8-stage manufacturing process
The kraft manufacturing line runs in two functional zones: pulping (stages 1–4) converts wood to fibre; papermaking (stages 5–8) converts fibre to roll stock. Most modern mills run both zones on the same site for energy integration. For the full end-to-end paper making process covering every paper grade, see our step-by-step pillar.
Stage 1, Wood preparation: Debarked logs are reduced to chips sized 12–25 mm long × 2–10 mm thick per TAPPI wood preparation standards. Chip uniformity directly controls cook quality; oversize chips under-cook in the centre, undersize chips over-cook on the surface.
Stage 2, Digester cooking: Chips enter the paper mill digester (batch or continuous Kamyr design) with white liquor (NaOH + Na₂S, sulfidity ~25–30%). Cooking runs at 170–176°C for about 2 hours for delignification per IPPTA kraft sulphate pulping reference. Yield is about 50% of dry wood weight as brown stock pulp, with ~5% residual lignin in the pulp, per the same IPPTA reference.
Stage 3, Brown-stock washing + screening: The cooked pulp is washed in counter-current vacuum drums or pressure diffusers to remove black liquor. Screens (slot 0.15–0.30 mm) remove knots, shives, and oversize rejects.
Stage 4, Optional bleaching: For bleached kraft, the brown pulp moves to a multi-stage ECF (elemental chlorine-free) pulp bleaching process, typically a D-Eop-D-P sequence. For brown kraft, this stage is skipped and the pulp goes directly to stock prep.
Stage 5, Stock preparation: Refining adjusts fibre length and freeness (target 350–500 mL CSF for sack kraft, 200–350 mL CSF for liner kraft). Wet-end chemistry adds sizing, retention aid, and wet-strength resin if needed.
Stage 6, Forming + pressing: Stock at 0.5–1% consistency is jetted from the headbox onto a moving wire. Water drains by gravity + foils + vacuum; the wet sheet (~20% solids) transfers to the press section where felts squeeze it to ~45–50% solids.
Stage 7, Drying: The sheet travels over 40–60 steam-heated cylinders at 110–130°C, exiting at 92–94% solids. Energy intensity for kraft drying runs 5–7 GJ per tonne of paper per IEA paper-industry benchmarks.
Stage 8, Reel + finishing: The jumbo reel is slit, rewound to customer reel sizes, and either shipped or routed inline to converting (bag-making, corrugating, sack tube extrusion).
5. The kraft pulping advantage, chemistry + recovery loop
What makes kraft pulping economically and environmentally viable is chemical recovery. The black liquor that leaves the digester carries dissolved lignin (organic) and spent cooking chemicals (inorganic). Instead of dumping it, modern kraft mills run a closed loop:
- Evaporation: black liquor concentrated from ~15% solids to 65–80% per IEA pulp and paper technology report.
- Recovery boiler: concentrated liquor burned; organic lignin generates steam (often supplying 60–80% of mill power); inorganic chemicals form a molten smelt of Na₂CO₃ + Na₂S.
- Causticising: smelt dissolved in water (green liquor) reacts with quicklime (CaO) → fresh white liquor (NaOH + Na₂S) ready for the next cook.
- Lime cycle: the byproduct calcium carbonate is calcined back to quicklime in a rotary lime kiln.
Recovery efficiency at well-run mills reaches ~90% per IPPTA chemical recovery technical paper, meaning <10% chemical makeup is needed per cook. This is the structural reason kraft dominates global chemical pulping: it pays for itself in chemical and energy savings within years of commissioning.
6. GSM ranges + grades by application
GSM (grams per square metre) is the most common buyer-facing spec for kraft paper. It's not the only spec that matters, burst index, tear index, ring crush, and tensile MD/CD also count, but it's the first filter buyers apply.
For corrugated boxes the buyer terminology differs: fluting medium is typically 100–200 GSM kraft; kraftliner (the outer face) is 125–440 GSM per TAPPI test methods.
7. Kraft paper applications by industry
Kraft paper is the most versatile pulp-based material on the market. The matrix below maps grades to industries:
Beverages-specific kraft is a growing sub-segment: kraft straws, kraft cup wraps, and kraft secondary packaging for craft beverages now use 90–200 GSM bleached or recycled grades with food-contact certification. Recycled kraft enters the mill as repulped fibre from sorted waste paper grades such as OCC, mixed paper, and old kraft sacks.
8. Decision matrix, which kraft type for your use case
Most kraft selection mistakes happen because buyers pick on GSM alone. The right kraft for a use case depends on three vectors at minimum: strength requirement, surface finish requirement, and food-contact / regulatory requirement.
The matrix above is a starting point. For high-stake applications (food contact, electrical, regulated industries), specify by functional standard (TAPPI test method, IEC dielectric class, FSSAI/FDA certification), not by GSM alone. If your application is sanitary or hygiene paper instead of packaging, see our tissue paper manufacturing process guide.
If you're a buyer with a specific spec, our supplier directory for kraft paper manufacturers lists verified mills by region, capacity, and grade specialisation.
9. Strength properties, what buyers should actually test
GSM tells you weight. The four tests below tell you whether the kraft will survive the job:
MD (machine direction) values typically run 2–3× higher than CD (cross-direction), which is why sack tubes are extruded with MD axial, a sack pulled in the wrong direction is much weaker.
10. Sustainability + recyclability
Kraft paper is one of the most defensible packaging materials on lifecycle metrics, with three caveats:
- Recyclability: Unbleached kraft is repulpable 5–7 times before fibre length degrades enough to drop strength below sack/corrugating grade per CEPI 2025 fibre cycle data. Bleached kraft recycles slightly fewer cycles due to brightness loss.
- Renewability: Wood inputs are from managed forests (FSC-certified mills source 60%+ from certified pools); kraft mills typically run on-site biomass cogeneration from lignin recovery, producing 60–80% of mill power internally.
- Caveats: Coated kraft (CCK, PE-coated) and wet-strength kraft are harder to recycle in standard streams, they need specialised facilities. Bleached kraft from non-ECF mills carries higher chlorinated effluent burden; ECF and TCF (totally chlorine-free) mills are now the global default per IEA paper-industry decarbonisation report.
For brand-owners citing kraft for green claims: use unbleached, uncoated, FSC-certified kraft for the cleanest LCA story.
Beyond softwood kraft, agro-residue fibres extend the sustainability story further. Bagasse, the fibrous residue from sugarcane crushing, is a strong non-wood alternative for converters wanting to mix or fully replace wood pulp. See our guide on sugarcane bagasse pulp sheet sourcing for verified Indian suppliers and grade specifications.
11. Kraft paper market + pricing
Global kraft paper demand was approximately 52 million tonnes in 2024, projected to reach 65 million tonnes by 2030 at a CAGR of ~4% per FAO Forestry production database 2024. The Indian kraft market alone was valued at over $1 billion in 2020 with growth in the mid-single digits annually per IPMA industry statistics, driven by e-commerce, cement, and packaged-food demand. Alternative-fibre kraft is also growing fast in India; see our bagasse plate making machine guide for the non-wood route.
Indicative kraft paper prices (mill gate, May 2026):
Prices are indicative ranges only, final pricing depends on order volume, MOQ, port-of-delivery, currency at order time, and supplier mill terms. USD to INR conversion at ₹96.28 per Morningstar / Google Finance 18 May 2026 rate. For live quotes use our kraft paper quote tool.
Multi-currency reference (top 10 paper-industry currencies, approx 18 May 2026 spot per 1 USD):
12. Starting a kraft paper plant, capex, licences, payback
For investors and machine-buyers researching a new kraft paper plant, the project structure breaks into four cost pillars:
USD to INR conversion at ₹96.28 per Morningstar / Google Finance 18 May 2026. Project costs are highly site- and capacity-specific; figures are indicative only.
Indian licence stack (typical requirements): - Industrial / SSI registration - Factory licence (State Labour Department) - Environmental clearance (Category-B by capacity, MoEFCC / SEIAA) - Consent-to-establish + consent-to-operate (State Pollution Control Board) - ISO 9001 + ISO 14001 (buyer requirement, not statutory) - BIS registration for specific grades - GST registration
Payback timing: A well-run 100 TPD recycled-kraft plant in India typically reaches operational breakeven in 18–24 months and capex payback in 4–6 years at 80% utilisation per IPPTA member-mill data. Virgin-fibre mills run longer paybacks (6–8 years) because of higher raw-material cost.
For machinery, the most cost-efficient kraft paper line specifications are available from established suppliers like Parason Machines, which offers turnkey paper machine solutions with stock prep, headbox, press, and dryer sections sized for 30–500 TPD output. For a broader supplier shortlist by region, see our paper mill equipment list and the WPM business directory.
A broader view of OEM choices is available in our comparison of paper mill machinery and equipment manufacturers, covering kraft-specific suppliers across Germany, Finland, Austria, India, and China by deckle width, speed envelope, and TPD capacity.
13. Choosing a supplier, kraft paper procurement checklist
Whether you're buying kraft rolls, kraft converting machinery, or a turnkey kraft plant, the supplier evaluation checklist is the same five categories:
- Grade specialisation: Does the mill actually make your grade? Many mills make 4–5 grades; very few make all 16.
- Capacity + MOQ: Match TPD and roll-width capability to your order volume.
- Certification stack: FSC chain-of-custody, ISO 9001/14001, food-contact certifications (FDA/FSSAI) if relevant.
- Geography + logistics: Inland mills add 10–18% freight to coastal export shipments; choose by destination port.
- Quality testing: Insist on TAPPI-certified test reports (T 403, T 414, T 494, T 822) per consignment, not annual averages.
Browse our kraft paper manufacturers directory for region-filtered shortlists. For a specific quote with grade + GSM + tonnage filled in, use the equipment inquiry form or request a technical consultation.
Wood preparation is the first stage of any chemical pulping line. For the full mechanical conversion sequence, see our guide on the chipping process in paper making.
