Testliner 2.

Testliner 2 is a recycled-fibre outer liner for corrugated boxes — the European standard mid-tier answer to the more expensive virgin kraft liner. You will find it on hundreds of millions of shipping boxes moving through European supply chains every year: brown, slightly uneven in tone, occasionally showing specks of printed ink from the old cartons it was made from. The "2" in the name is a FEFCO grade number, not a quality ranking. FEFCO's grading system runs Testliner 1 (heaviest and strongest), Testliner 2 (standard workhorse), and Testliner 3 (lighter duty, higher recycled content). Testliner 2 is the family's centre of gravity, the weight at which European packaging converters made their peace between cost and structural performance. If you have ever opened a cardboard box and noticed that the outer face looks almost like kraft liner but slightly duller, slightly more textured on the cut edge — that is most likely Testliner 2 WPI-g-000889.

What it's used for

Testliner 2 is at home wherever a corrugated shipping box needs a respectable outer face at a price below virgin kraft liner. That covers a lot of ground.

The dominant application is the outer liner of single-wall corrugated boxes destined for the domestic European market. A typical construction runs Testliner 2 on the outside, fluting WPI-g-000864 in the middle at 112–127 g/m², and either another layer of Testliner 2 or a lighter Testliner 3 on the inside face. For non-critical goods — dry groceries, hardware, stationery, clothing — this all-recycled construction performs well and prices sharply against virgin alternatives.

E-commerce packaging has driven the largest share of Testliner 2 growth in the past decade. When a fulfilment warehouse boxes a hundred thousand orders a day, shaving three euros per thousand boxes off the liner cost adds up quickly, and the structural requirements are modest: the box must survive a journey measured in days, not ocean crossings. Testliner 2 at 150 g/m² handles that load case comfortably. The argument for upgrading to kraft liner only enters when export transit times extend, when stack heights on pallets increase, or when humidity during storage becomes a specification variable.

A more specific use case: European FMCG brands shipping ambient grocery products to retailers typically specify dual-liner corrugated with Testliner 2 on both faces, a construction the trade calls "full testliner." It is cheaper than a kraft-outer construction and meets most retailer transit testing protocols for dry goods at medium stack heights. The same brand with a premium product line might specify kraft liner WPI-g-000888 on the outer face only, keeping Testliner 2 inside to recover part of the cost premium.

One underappreciated application: Testliner 2 as the inner liner in boxes where the outer liner is a printed, higher-quality sheet. In those constructions the outside face carries brand graphics on white-top liner or semi-bleached kraft, while Testliner 2 on the inside supplies structural contribution at low cost. The box presents well, survives the transit, and the buyer never sees the inside face.

Origins and history

Testliner is a post-war European invention — or more precisely, a post-war European adaptation to constraint. The 1950s and early 1960s in Europe were a period of wood fibre scarcity relative to demand. North American virgin kraft liner was available but expensive to import. Northern European forests had been heavily harvested during the war years and were still recovering. At the same time, the industrial and consumer economies were expanding rapidly, and corrugated packaging demand was growing with them.

The practical solution was recovered fibre. Old corrugated cartons — the spent shipping boxes of the post-war consumer economy — were available in increasing quantities as supermarket chains and mass-market retailers grew. European paper mills, particularly in West Germany, the Netherlands, and the United Kingdom, developed processes to turn this recovered material into a usable liner grade. The result was a sheet that could function as a liner at competitive prices, though with lower burst strength than the virgin grades it substituted.

The name "Testliner" carries a technical provenance. The CEPI (Confederation of European Paper Industries) recovered-fibre classification system included a strength-testing regime for assessing the quality of sorted recovered paper feedstock, and the liner grades produced from this feedstock took a name that signalled their relationship to that testing discipline. This was not a marketing choice but an industrial one: buyers needed a clear signal that the sheet was made from tested recovered feedstock, not indiscriminate mixed waste.

FEFCO formalised the numbering in the 1960s when it published its code of international paper and board specifications. The Testliner 1 / 2 / 3 hierarchy locked in the industry's vocabulary for ordering and trading the grades. Testliner 1 was the strongest and heaviest, typically 150 g/m² and above, made from the cleanest DLK (double-sorted kraft liner) feedstock. Testliner 2 was the mid-tier standard at 115–200 g/m², made from a blend of OCC and DLK. Testliner 3 was lighter-duty, with a higher proportion of lower-quality mixed recovered fibre.

The modern context adds a regulatory dimension. The EU Deforestation Regulation (EUDR), which entered its compliance phase in 2025, requires that virgin wood fibre in products placed on the EU market be traceable to non-deforested land. That requirement has accelerated the substitution of virgin kraft liner with Testliner 2 in some supply chains, particularly for brands with sustainability commitments that are easier to satisfy with an FSC Recycled certified sheet than with FSC Mix virgin kraft from complex multi-country fibre sourcing. CEPI data consistently shows European recycled containerboard production running at over 80% of total containerboard output, with Testliner 2 occupying the largest single grade position within that.

How it's made

The raw material for Testliner 2 is a blend of OCC (old corrugated containers) and DLK (double-sorted kraft liner) in proportions that vary by mill and market, typically 60–80% OCC with the balance in DLK. DLK commands a premium over OCC because it is cleaner, stronger-fibred, and produces a brighter finished sheet. Higher DLK proportions give a sheet that approaches Testliner 1 characteristics; lower DLK proportions slide toward Testliner 3 territory.

The bales arrive at the mill's pulper — a large drum or tub with rotating agitators — where the recovered paper is mixed with process water and mechanically dispersed into a slurry at 4–6% consistency. The pulper also removes obvious contaminants: plastic films, metal staples, adhesive labels. The resulting pulp passes through a screening sequence — coarse screens to remove large rejects, fine screens to remove ink particles and fibre bundles, cleaners to remove heavy particles by centrifugal separation.

A critical process step is the top-ply construction. Testliner 2 is almost universally made on a machine with two forming layers. The bottom ply uses lower-quality furnish — higher OCC content, shorter average fibre — while the top ply uses a better-quality furnish, typically higher DLK content and more carefully screened. The top ply is the surface that faces outward on the finished corrugated box: its quality determines printability and surface strength. This two-layer strategy allows mills to optimise fibre cost without compromising the customer-facing surface. A cross-section through a sample of Testliner 2 reveals the interface between the two layers as a faint density variation; on a fresh cut edge, the top ply often appears slightly denser and smoother.

Why does Testliner 2 have lower burst strength than kraft liner at the same GSM? The answer is hornification. When a cellulose fibre is wetted and then dried — which happens every time a corrugated box is recycled — the fibre wall partially collapses and the hydroxyl groups responsible for inter-fibre hydrogen bonding become less accessible. This is hornification, and it is irreversible. Each recycling cycle reduces average fibre length by 10–20% and reduces bonding potential further. Virgin kraft fibre has never been through this process; Testliner 2 feedstock has been through it at least once, often two or three times. The cumulative effect is a sheet that bonds less completely and therefore delivers lower burst and tensile strength per gram of fibre than virgin kraft. Good process engineering narrows the gap but cannot close it.

The finished sheet is wound to parent rolls and converted at the mill into the slit rolls that corrugated board plants use. Surface sizing — typically with starch, applied at the size press — is standard and critical for moisture resistance and surface bonding during corrugation.

Specs that distinguish it

The numbers that separate Testliner 2 from its siblings and from kraft liner:

• Basis weight — 115–200 g/m², with 125, 140, and 150 g/m² the most common commercial weights. Measured to ISO 536.
• Burst index — typically 4.5–5.5 kPa·m²/g (ISO 2758 Mullen test). Substantially below virgin kraft liner at comparable GSM (kraft liner 140 runs 6.5+ kPa·m²/g). This gap is the fundamental performance trade-off.
• Cobb value (60 s) — 20–30 g/m² on well-sized grades. Above 35 is a signal of under-sizing or wet-end chemistry issues.
• Brightness (ISO 2470) — 28–32%. Slightly higher than virgin kraft liner because the multi-stage washing during recycled pulp processing removes some coloured tannin compounds. If brightness exceeds 35%, the mill has added optical brightening agents or partially bleached the furnish — watch for this, as it adds cost without structural benefit.
• RCT and SCT — increasingly specified for recycled liner grades rather than burst alone. RCT index for Testliner 2 at 150 g/m² typically runs 2.0–2.8 N·m/g; burst underweights the short-fibre effect and can give a misleadingly high number on well-calendered sheets. SCT is the better predictor of ECT performance.

At equal basis weight, the gap between virgin kraft liner and Testliner 2 on burst index runs 25–35%. The price gap runs 15–20% in typical European spot markets. Whether the cost saving justifies the structural trade-off depends entirely on the application.

Variants and family

Testliner 2 sits in the middle of a three-grade family, all made from recycled fibre, that spans most of the European corrugated liner market:

Testliner 1 is the premium end — typically 150 g/m² and above, made from the cleanest DLK feedstock, with burst indices approaching (but not reaching) virgin kraft performance. Mills sometimes market Testliner 1 as a drop-in substitute for kraft liner in domestic applications. The fibre cost for Testliner 1 is significantly higher than TL2 because clean DLK is a limited and contested recovered paper grade.

Testliner 2 (this grade) WPI-g-000889 — the standard, the default, the commercial centre of gravity. 115–200 g/m², OCC and DLK blend, burst index 4.5–5.5.

Testliner 3 is lighter duty — typically 100–140 g/m², higher mixed waste content, lower burst and RCT. Used as inner liners in lower-cost single-wall constructions and in applications where structural loading is minimal. Also used as inner liner in dual-testliner constructions alongside Testliner 2 on the outer face.

White-top Testliner is a premium variant with a bleached or semi-bleached top ply applied over a standard recycled-fibre base. The white surface enables higher-quality print than natural brown testliner while retaining the recycled-fibre cost advantage in the base. It competes with white-top kraft liner in retail shelf-ready packaging applications. The top ply is typically 15–25 g/m² of bleached chemical pulp; the base is standard TL2 furnish.

Outside the strict TL family, a related grade worth knowing is the generic Test Liner WPI-g-000863 entry in the WPI database, which captures the broader historical category before the FEFCO number system fully standardised.

Buying notes

Three things worth checking before you commit to a testliner purchase:

"Kraftliner" in the sales pitch, testliner in the box. Some converters and distributors use "kraft liner" loosely to mean any brown liner grade that performs adequately. If a spec sheet uses the word "kraft" but the fibre composition shows any recycled OCC content, the sheet is Testliner regardless of the marketing language. Ask explicitly for a fibre composition analysis. Virgin kraft liner runs 80–95% softwood tracheids on fibre microscopy; Testliner 2 shows significant short-fibre hardwood and mixed cellulose populations. The burst index will also tell the story: below 6.0 kPa·m²/g at 140 g/m², you are not buying kraft liner.

Brightness above 35% is a warning, not a feature. On a standard Testliner 2, ISO brightness runs 28–32%. Anything above 35% means the mill has added optical brighteners, partially bleached the furnish, or blended in a significant proportion of office waste paper (which is partially bleached and lighter). None of these is necessarily wrong, but they add cost without structural benefit and can affect the sheet's performance in printing and surface-coating applications. Confirm the ISO 2470 value on a physical sample.

RCT matters more than burst for recycled grades. Burst strength measures rupture resistance under outward hydraulic pressure — a failure mode that rarely governs corrugated box performance. Box failure under stacking loads is a compression event; the relevant metrics are RCT or SCT (which predict ECT at the board level). Well-calendered Testliner 2 can show burst numbers that overstate its compression performance because calendering densifies the sheet and improves the burst result without improving compressive strength proportionally. If your application is high-stack or export, specify RCT and hold it. Typical minimum RCT index for structural Testliner 2 at 150 g/m² is 2.2–2.5 N·m/g.

For sustainability certification: FSC Recycled is the compliant choice for testliner grades, not FSC Mix or FSC 100%. FSC Recycled certifies that the entire fibre input is post-consumer or pre-consumer recovered paper — appropriate for a grade made from OCC and DLK. FSC Mix would imply a combination of virgin and recycled fibre, which misrepresents the grade. Under EUDR, FSC Recycled testliner has a simpler compliance path than virgin kraft because recovered fibre is exempt from the deforestation traceability requirement.

Related reading

• Kraft paper — the complete guide — the hub for the kraft and liner family, with context on where Testliner sits in the competitive landscape.
• Fluting — the corrugated medium that runs between the two liner faces.
• Ring crush test (RCT) — the compression metric that matters most for recycled liner grades.
• Edge crush test (ECT) — the board-level stacking-strength metric your liner feeds into.

Sources

• FEFCO — Code of International Paper and Board Specifications — source for the Testliner 1/2/3 grade numbering system.
• CEPI — Key Statistics 2023: European Pulp and Paper Industry — European recycled containerboard production share data.
• ISO 7263-1:2018 — Corrugating medium: Determination of flat crush resistance after laboratory fluting — referenced for fluting test methodology context.
• TAPPI T-403 — Bursting strength of paper — burst index test methodology.
• McKinlay, A. — Paper and Board Manufacture (TAPPI, 1982), Ch. 11: Recycled fibre processing — background on hornification and recycled fibre strength degradation.