CCK Release Paper Explained: How Clay-Coated Kraft Liners Work — and How to Spec Them

Updated July 2026 · A materials-side guide for plant engineers, converters, and procurement.

CCK release paper is a clay-coated kraft release liner: a kraft-paper base sealed on one side with a fine clay (kaolin) layer and then a silicone coating, so a pressure-sensitive adhesive peels away cleanly at a controlled release force. That three-part construction – kraft, clay, silicone – is why one CCK grade dispenses smoothly on a high-speed converting line while another drifts mid-reel. This guide explains the mechanism, how to read a release-force spec, how to choose basis weight, and how to diagnose the faults that stop a line.

What Is CCK Release Paper?

CCK (clay-coated kraft) release paper is a kraft-paper liner coated on one side with a fine clay layer and then silicone, so that a pressure-sensitive adhesive releases cleanly and at a predictable force. The clay seals the porous kraft surface so the silicone stays on top of the fibres instead of soaking in – and that single detail is what keeps release force uniform roll to roll.

To understand why the clay matters, picture the alternative. Bare kraft paper is porous. Coat it with silicone and the silicone wicks into the fibre network unevenly, so the amount left on the surface – the part that actually controls how the adhesive lets go – varies along the reel. Release force then changes as you run. The clay (kaolin) coat gives the silicone a smooth, closed surface to sit on. As the Pressure Sensitive Tape Council notes, a clay-coated kraft surface is “closed” and “allows less silicone,” which is both a cost lever and a consistency lever.

A finished CCK liner is a stack of four functional layers:

• 1. Kraft base – supplies strength, stiffness, and tear resistance for high-speed dispensing.
• 2. Clay coat – the kaolin barrier that holds silicone on the surface (silicone holdout).
• 3. Silicone coating – the low-surface-energy release layer the adhesive peels from.
• 4. Functional reverse-side coating (optional) – a back coat that improves lay-flat, dimensional stability, and printability.

That last layer isn’t a detail. The move from an open (uncoated) reverse side to a functional reverse-side coating is exactly what turned CCK from a compromise liner into a die-cutting workhorse. If you want the broader family context first, see our primer on how a release liner works before you go deeper on clay-coated kraft.

CCK vs PCK, Glassine, SCK & PET: Which Release Liner Wins When

CCK differs from PCK in one place that decides everything: the release surface is mineral clay, not extruded polyethylene. That makes CCK stiffer, more heat-stable, and paper-recyclable, while PCK (PE-coated kraft) lays flatter and resists moisture better. Neither is “best” – the winner depends on your climate, your die-cutting precision, and your recycling obligation.

The contrarian aspect you won’t find on most product pages: CCK isn’t automatically #1. According to the most cited industry figures, clay-coated kraft represents about 44% of the release-liner market, PE-coated kraft is 40%, and glassine plus SCK total near 12% with film liner the remaining 3% (AWA “Pressure-Sensitive Graphic Films” study, through Adhesives Magazine). But the worldwide number hides an important market distinction: In Europe, CCK has about 77% market share, while in the US, PE-coated kraft dominates at approximately 49%, with CCK coming in at 40%. That’s due to historical context-US CCK grades were conventionally shipped with an open reverse side, which was detrimental to dimensional stability. As a result, US converters favored PCK.

Think of this table as a guide to decision-making, not a scoreboard. Opt for CCK for paper recyclability, resistance to heat, and consistent printability on the reverse for standard label and tape converting applications. Choose glassine if precision die cutting and visual transparency are key; the densified surface of glassine provides cleaner cuts than CCK, which can experience cracking in its coating when subjected to very fine and detailed die cuts. SCK serves as a cost-effective balance, PCK is the go-to for stable lay-flat performance in high humidity and composite lamination, and PET is best when the process is primarily governed by high temperature or exceptionally thin material gauges. If the decision rests between CCK and a paper-based alternative, refer to our comparative guide on glassine release liner for in-depth information on the latter; the glassine release liner grades page lists product specifications.

Before honing in on CCK, consider this broader perspective of the landscape. The nine liner types detailed below are organized according to base material and release class-a classification process routinely employed by converters when narrowing down carrier options.

The EU–US split, and how CCK improved

The label market has long been dominated by two paper-based release liner options — clay coated kraft paper and PE-coated kraft — and the AWA global market study is the reference most of the industry quotes for the split. Yet the reason Europe CCK reaches about 77% while US converters historically leaned on PCK sits in paper production history, not marketing. For years, US clay-coated papers shipped with an open reverse side; European mills moved to coat the reverse too, so today CCK grades are mainly coated on both faces.

That functional reverse side coating — a CCK paper with a functional reverse side — is what let manufacturers improve the dimensional stability of the base. Over the years, mills refined CCK paper to improve the dimensional response to humidity, and in many jobs PE carriers were replaced with dimensionally stable CCK papers. The result: for most converting, CCK paper alone is an efficient, good release liner solution, and it is only in high-humidity extremes that PE-coated paper remains the premier option. CCK and PE grades can also be combined into a hybrid when a job needs both a paper face and a plastic moisture barrier.

The siliconizing properties of the CCK coating matter as much as the base. Because the properties of the CCK coating give a CCK coating with a strong, closed clay surface, the silicone sits on top of the coated paper rather than soaking in — the side coating does the releasing, not the fibre. That, plus the fact these clay-coated papers recycle in the paper stream, is why CCK papers offer improved sustainability over plastic grades and why so many converters now specify these grades as release liner of choice. Using this more advantageous release construction is, increasingly, the default across the wider release liner market.

How to Read a CCK Release-Force Spec (FINAT FTM 3)

A release-force value only means something once you know the test speed behind it. The release force figures presented in most CCK datasheets are provided in grams per inch (g/in), determined through FINAT test method FTM 3. This method measures liner release from the adhesive at low speed and a 180° peel angle. This value primarily indicates liner performance during storage and slow handling-it doesn’t necessarily reflect behavior on a fast-moving dispensing line at 150 m/min.

Categorize release-force values into three practical ranges, and align the appropriate range with your adhesive and line speed:

Here’s where confusion often arises. FTM 3 is a slow-speed test, and typically, release force increases with increasing peel speed. This means a product listed with a low-speed release force of 20 g/in may unexpectedly pop or break web when used at higher speeds on an accelerated line.

One methodical way to reach a target band is using our release force selector; and once you’re ready to match numbers to a real grade, the CCK release paper specifications list the full tested ranges.

Choosing Basis Weight and Caliper for Labels, Tape, and Composites

Choose basis weight by application, not preference, lighter for labels, heavier for tape and composite cure. The kraft base of a CCK paper carries the mechanical load of die-cutting and dispensing, so caliper decides whether a die cuts cleanly to the liner without cutting through it, and whether the web stays flat under humidity.

Two basic rules of thumb help select basis weights fairly. First, the softer the liner, the greater the potential for the die to deform the web – an obvious die-cutting challenge identified in label-tech lit. Second, greater weight doesn’t mean better: the added caliper also raises costs, and adds stiffness that will counteract the needs of tight-radius wrap labels. If you’re still developing your total construction, facestock, adhesive and liner, start with our label stock selection guide, and for cold-chain jobs cross-check the liner against our freezer label materials notes.

Silicone Coating Chemistry: Solvent-Based, Solvent-Free, and Water-Based

The silicone chemistry sets the VOC profile, the cure behaviour, and how well the coating stays put, its “holdout.” Most CCK is made in one of three chemistries, and each pairs best with a specific adhesive and compliance target.

Two silicone concepts explain most failures. Silicone holdout is the coating staying where it should – on the clay-coated surface. Silicone transfer is the opposite: the silicone migrates onto the adhesive and kills its tack. Holdout is what you pay the clay coat for; transfer is what makes a liner fail. Silicone coat weight is around 0.8 to 1.5 g/m², measured by X-ray fluorescence. For a food-packaging converter, that usually means specifying solvent-free silicone to hold migration below the food-contact limit; for a high-speed label line, it means demanding a documented coat-weight window on every lot. The release-coating chemistry itself is well characterised in the patent record — see, for example, USPTO patent US6806339B2 on silicone release-coating compositions.

“We isolated 18 silicone-polymer-ratio combinations against the FINAT FTM 3 markers before we settled on our CCK release-force specification. Every batch of the final formulation then produced the same release-force range, whether it ran in Bangkok or Vietnam. Release-force repeatability is a procurement choice, not a marketing claim.”

A supplier’s most practical signal to demand is batch-to-batch consistency expressed as a coefficient of variation. Guanma’s coating lines, for example, bring release-force variation on the reel to below 2%, by sampling FINAT FTM 3 at reel start/middle/end on every slit.

Troubleshooting CCK Release Paper: 6 Converting-Line Faults

The most common CCK converting fault is release-force drift mid-reel, caused by silicone bleeding into the kraft where the clay coat is thin or uneven, confirmed by FINAT FTM 3 sampling at reel start, middle, and end. Most line stoppages trace back to one of six root causes. Use the table below as a diagnostic map: match the symptom, then attack the cause, not the symptom.

A field example fleshes the first row. A converter loads a 50,000 m roll, and peels its first 8,000 m without trouble; on the third reel the release force shoots from about 15 g/in to 60 g/in. Nothing changed; the silicone had bled into the kraft where the clay coat was thin. The solution is upstream in the coating, not downstream in the machine: a closed clay layer and start/middle/end release sampling on every slit. How a clay coat holds silicone under die pressure is documented material science — see patent WO2005052082A1 on structured paper release liners. You’ll meet this limitation again and again: the finest, most elaborate die-cuts sometimes belong on glassine, not CCK.

Reading a CCK Spec Sheet: Standards and What to Verify

A test method tells the lab how to measure the liner, not how the liner must perform for you. Your own qualification file holds the performance spec. Know which standard governs which property; learn to read a CCK datasheet instead of trusting a badge.

• FINAT FTM 3 / FTM 2 — release force (low-speed 180° peel) and peel adhesion (90°). The core release measurements.
• ISO 536/ISO 534 – basis weight and thickness. The baseline dimension.
• ISO 5630/ ISO 8791 – dimensional stability in humidity and surface smoothness (Bekk).
• FDA 21 CFR 175.300 + BfR XXXVI – food-contact scope for the silicone/resinous coating layer.

Food-contact references are the ones most often answered incorrectly. The silicone-resinous coating is regulated by FDA 21 CFR 175.300 — the standard for polymeric and resinous coatings — not by 21 CFR 175.105, which relates to adhesives. Both can appear on a self-adhesive construction, but they control the respective layers. “175.300 compliant” describes the scope of the resinous coating, not blanket food approval. For regulated pharmaceutical/food work, confirm grade; see our pharmaceutical label materials page for full documentation. When you solicit a datasheet, request lot-level release force data and standard revision names, a CCK release paper spec sheet should name them.

Are CCK Liners Recyclable? The Sustainability Picture

Yes, CCK release paper is recyclable through standard paper streams, because the silicone is stripped during pulping and the kraft fibre re-enters the mix. That paper recyclability is CCK’s main sustainability strength versus PE coated and PET liners where the plastic barrier complicates separation. Paper-based CCK grades which are FSC and PEFC certified then also provide verified chain of custody.

One honest caveat: technically recyclable doesn’t equate to recycled. The release liner is the label industry’s hidden waste stream – much used liner continues to end up in landfill because the collection and de-siliconisation infrastructure is so limited. Liner-recycling take back schemes exist but they depend on the converter having the volume and logistics to participate.

If sustainability is on the agenda treat end of life of your liners as a sourcing question, not an add-on, and ask what end-of-life pathway the supplier actually supports. Other material considerations sit in our release paper and liner options overview.

Industry Outlook: Where Release-Liner Materials Are Heading (2026)

Regulation, not raw demand, is the force reshaping when a converter still specs paper CCK versus migrates away from it. The risk is concrete: a converter that misjudges the shift can be left holding non-compliant liner stock when the 70% recyclability cut-off lands in 2030, or paying to re-qualify a substitute liner against a deadline.

The EU’s Packaging and Packaging Waste Regulation (PPWR) 2025/40 became law on February 11 2025 and takes effect on August 12 2026; packaging won’t be allowed on the market if less than 70% recyclability is met from 2030. Paper-based CCK gets favourable consideration under this legislation. However the pressure to adapt is accelerating two forces which undermine demand for paper-liners; linerless label technology on very high-speed applications, and thin-liner downgauging – reduced basis weight in order to reduce per label cost and carbon.

Evidence of direction can be found in recent patents, e.g., a 2024 supercalendered-kraft release-liner patent utilizing recycled fibre content points towards lighter, more recyclable paper, not plastic-centric constructions. Market data on liner volumes – order-of-magnitude – points to a mid-single digit growth range for release-liners overall. A concrete action for 2026: before your next liner contract, audit your highest-volume SKUs for downgauge and linerless exposure, and ask whether each one still needs the liner weight it currently carries. A high-volume beverage-label converter, for instance, may drop the liner entirely on its top SKU with a linerless system, while a pharma converter keeps paper CCK for its documented compliance trail — the same regulation pushing two plants in opposite directions.

Frequently Asked Questions