Selecting the optimal containerboard combination (Testliner 1/2/3, Recycled Fluting, Semi-Chemical Fluting, White Top Liner, and Kraftliner) is the core technical determinant of carton stacking strength, box compression resistance (BCT), and unit packaging cost. Turkish paper mills produce top-tier containerboard grades that combine high burst strength, excellent runnability at 300+ m/min corrugator speeds, and competitive export pricing.
1. Technical Classifications: Testliner vs Fluting vs Kraftliner
Containerboard is split into two foundational categories: Linerboard (the flat outer and inner facings of the corrugated board) and Fluting/Medium (the wave-shaped fluted core that provides cushioning and vertical crush resistance).
Testliner is produced from recycled paper fibers, enhanced through surface sizing with cationic starch to achieve strong burst and scuff resistance. Testliner 1 offers superior virgin-like properties (Burst Index > 2.6 kPa·m²/g), Testliner 2 represents the industrial workhorse (Burst Index 2.0 - 2.4), and Testliner 3 serves cost-sensitive applications. Fluting is engineered for Short Span Compression Strength (SCT) and Concora Medium Test (CMT), preventing board collapse under heavy warehouse stacking loads.
Mechanical Specifications Comparison across Primary Paper Grades
| Paper Grade | Standard GSM | Burst Index (kPa·m²/g) | Cobb60 (g/m²) | SCT CD (kN/m) @ 125 GSM | Primary Application |
|---|---|---|---|---|---|
| Testliner 1 (TL1) | 100 — 175 | 2.6 — 3.0 | 25 — 32 | 1.85 — 2.10 | High-end export cartons & printed boxes |
| Testliner 2 (TL2) | 90 — 200 | 2.0 — 2.4 | 28 — 35 | 1.65 — 1.85 | Standard industrial corrugated packaging |
| Testliner 3 (TL3) | 80 — 160 | 1.6 — 1.9 | 32 — 40 | 1.45 — 1.65 | Economical secondary shipping cartons |
| Recycled Fluting | 80 — 160 | 1.4 — 1.8 | Not sized (>60) | 1.70 — 2.20 | B, C, E, micro-flute corrugated core |
| Semi-Chemical Fluting | 110 — 180 | 1.8 — 2.4 | Controlled (35-45) | 2.30 — 2.80 | Heavy-duty agricultural & frozen goods export |
| White Top Testliner | 125 — 200 | 2.4 — 2.8 | 25 — 30 | 1.80 — 2.15 | High-definition flexo & retail POS boxes |
2. The Engineering Link: Calculating Box Compression Test (BCT) from Paper Specs
Corrugated converters must guarantee that finished boxes do not crush under multi-pallet warehouse stacking. The standardized McKee Formula bridges the gap between raw paper specifications and finished box compression strength (BCT):
BCT = 5.87 * ECT^0.51 * (t * Z)^0.49 (where ECT is the Edge Crush Test derived from liner and medium SCT values, t is board caliper, and Z is box perimeter). By increasing the SCT value of the fluting from 1.6 kN/m to 2.1 kN/m, converters can reduce the liner grammage from 140 GSM to 125 GSM while maintaining the same BCT, saving 8-12% in raw material cost.
3. How to Specify a Reel Order: The Buyer's Checklist
A precise order prevents most quality disputes. When you request a quotation for reels, give the mill: the paper grade and grammage (GSM) with tolerance; the reel width and the tolerance you can accept; the core inner diameter (commonly 76 mm or 150/152 mm, depending on the mill and your unwind stand); the maximum reel outside diameter and weight your handling equipment can take; the number of splices allowed per reel; the moisture target; and the test results you expect, such as burst index, Cobb60, SCT or CMT.
Also state the packaging (wrapping, edge protection, banding), the destination port, the preferred container type and the incoterm. A complete specification lets the mill confirm availability quickly and lets Dash quote a delivered price without rounds of clarification questions.
4. Choosing the Right Grade for Your Box
For general shipping cartons, a Testliner 2 outer with recycled fluting is the standard economical construction. For export boxes that will meet humidity, cold storage or long sea transit, choose a liner with a lower Cobb value and a fluting with higher CMT/SCT, or add a semi-chemical fluting. For retail-ready and printed boxes, a white-top liner provides the print surface, while kraftliner offers the highest strength and moisture resistance for produce and heavy goods.
Every step up in grade costs more per ton but can allow a lighter grammage for the same box strength, so compare the cost per box, not the cost per ton.
5. Receiving, Storing and Testing Reels on Arrival
Paper is hygroscopic: it takes up and gives off moisture depending on the surrounding air. Keep reels wrapped and stored on pallets or on their side on a dry floor, away from open doors, and let reels reach the plant temperature before unwrapping if they travelled in a very cold or hot container. Handle with clamp or core-tip equipment; a dent on the edge can cause web breaks on the corrugator.
On arrival, check reel count and weights against the packing list, inspect the wrapping for water marks and record the reel identification numbers. Send samples to your lab for GSM, moisture, burst and Cobb before the reels go on the machine, and report any deviation to the supplier promptly, in writing and with photographs.
6. How Containerboard Is Made: Recycled and Virgin Fibre
Containerboard is the family of papers used to make corrugated boxes. It is made from fibres: either recycled fibres from used cardboard, or virgin fibres from wood. The choice of fibre largely decides the strength, colour and price of the paper.
Recycled grades such as testliner and recycled fluting start as OCC and other recovered paper. The fibres are separated in a pulper, cleaned, mixed with starch and other additives, and formed on a paper machine into a continuous sheet that is dried and wound into a jumbo reel. Virgin grades such as kraftliner come from wood chips cooked in a chemical process (the kraft process) that keeps the fibres long and strong. Long fibres give higher strength and better resistance to moisture, which is why kraftliner costs more.
Between the two are blended grades. A mill may add a share of virgin or high-quality fibre to a recycled base to raise the strength of a top-grade testliner, or apply a white top layer of bleached fibre to give a printable surface. Knowing this helps you understand why two papers of the same grammage can behave differently and why their prices differ.
7. Grammage, Width and Reel Weight in Practice
Three numbers describe most of a reel: the grammage in grams per square metre, the width in metres and the length of paper wound on it. They let you calculate the weight and check what you are being charged for.
Reel weight in kilograms = width (m) × length (m) × grammage (g/m²) ÷ 1,000.
Worked example: a reel 2.0 m wide and 6,000 m long of 125 g/m² paper weighs 2.0 × 6,000 × 125 ÷ 1,000 = 1,500 kg. If the mill delivers the same paper in a 1.5 m width, the same length weighs 1,125 kg. A full container of about 20 to 26 tons therefore holds roughly 13 to 17 reels of the first size, depending on core weight and packaging.
Why this matters: the price is per ton, but the box maker cares about area. A heavier grammage gives more strength but fewer square metres per ton. A lighter grammage gives more boxes per ton but must still meet the strength you need, which is why the best choice is the lightest grade that reliably passes your box tests.
8. Why Humidity Changes Paper Strength
Paper is made of cellulose fibres, and cellulose absorbs water from the air. As the moisture in the paper rises, the bonds between fibres weaken and the sheet becomes softer and weaker. Compression strength can fall noticeably in humid conditions, and boxes that are strong in a dry warehouse can collapse in a humid port or cold store.
This is why specifications refer to standard conditions and why suppliers use sizing agents to slow water uptake. It also explains practical rules: keep reels wrapped until use, avoid storing them directly on damp floors, and let reels warm up before unwrapping if they have travelled through a cold climate.
For export boxes that will face a humid sea voyage or cold-chain storage, choose paper with a lower Cobb value and a fluting that keeps its strength when damp, and consider that the box may need a slightly higher grammage than the same box used only indoors.
9. Common Mistakes When Buying Reels
Buying on price per ton alone. A cheaper paper that needs a heavier grammage or causes more breaks on your machine can cost more per box. Compare cost per box and machine efficiency.
Ordering without stating the machine limits. If you do not specify core size, maximum reel diameter and weight, splices allowed and width tolerance, you may receive reels that your unwind stand cannot handle.
Ignoring the test conditions. Values from different laboratories are only comparable if the method and conditioning are the same. Ask which standard was used.
Skipping the trial order. The best way to judge a paper is to run it. Start with a trial quantity, record runnability, waste and box test results, then commit to larger volumes.
Poor storage on arrival. Reels stacked in a wet corner or left unwrapped in a hot warehouse lose quality that the mill cannot be blamed for. Agree handling rules with your warehouse team.
