Release Paper.

Release paper is the silicone-coated substrate that makes every peel-and-stick label in the world physically possible. Every retail price tag, every pharmacy prescription sticker, every Amazon shipping label, every bar-code decal on a warehouse tote, every wound-care bandage, every self-adhesive postage stamp, every roofing-membrane underlayer — all of them exist on top of a sheet of silicone-coated paper until the moment of application, when the release paper is peeled off and discarded. It is the invisible enabler of the modern label industry, running to roughly five million tonnes globally per year WPI-g-000873. The defining technology is not the paper itself but what is laid on top: a thin, cured film of polydimethylsiloxane — PDMS — the silicone elastomer that gives the surface its engineered, controlled low-adhesion. A pressure-sensitive adhesive (PSA) applied to the face stock above sits on that silicone film, bonding firmly enough to survive a supply chain but releasing cleanly when the label is dispensed, typically at a measured release-force of 5 to 80 centinewtons per inch. Everything about release paper is an exercise in negative chemistry: how little can you stick while still holding on.

What it's used for

The overwhelming majority of the world's release paper ends up under a pressure-sensitive label. The global PSA label market is the single largest release-paper consumer by tonnage, and within it, package labels — the retail barcodes on shampoo bottles, the dosage labels wrapped around pharmaceutical vials, the product data stickers on industrial equipment — are the highest-volume application. Glassine-based release paper WPI-g-000899 dominates the thin-carrier end of this market; super-calendered kraft takes the heavier tickets.

Logistics and shipping labels are the second great application, and the one that has grown fastest this century. Amazon alone generates in the order of six billion shipping labels per year; UPS, FedEx, DHL, and the postal operators collectively run into the tens of billions. Every one of those labels — the thermal-transfer and direct-thermal ones included — sits on release paper during printing, feeding, and application. Thermal-transfer label stock and high-speed labeler webs have driven a specialty segment of tight, uniform release-force release paper built for automated dispensing at 30,000 labels per hour.

Outside labels, release paper is quietly pervasive. Medical adhesives — wound-care dressings, surgical drapes, transdermal drug patches — use medical-grade release paper qualified for sterile processing. Roofing and construction use it as a peel-off carrier for self-adhesive bitumen membranes, flashing tapes, and house-wrap; workers peel the release paper away on the roof to expose the adhesive just before placement. Automotive decals, graphic vinyl, and paint-protection films all rely on release paper during lamination and transport. Tamper-evident security seals, self-adhesive postal stamps, diaper and feminine-hygiene adhesive-backing assembly, flexible printed-circuit-board bonding films, and laminated-glass interlayer handling all consume significant tonnages. The major global producers are Mondi (Austria — one of the two global leaders), UPM Raflatac (Finland), Ahlstrom (Finland/France), Loparex (US and Netherlands), Sappi (South Africa and global), and Delfort Group (Austria).

Origins and history

The release-paper story starts with a problem in adhesive chemistry and is resolved by a breakthrough in silicone chemistry. The adhesive side of the story begins in Los Angeles in 1935, when R. Stanton Avery — a 28-year-old inventor working out of a rented loft with a second-hand printing press — founded Kum Kleen Adhesive Products (shortly renamed Avery Adhesive Label). Avery built the first practical self-adhesive label: a printed face stock pre-coated with pressure-sensitive adhesive and mounted on a temporary backing, ready to peel and apply. The central engineering problem was that backing. The PSA had to sit on something until the moment of use, without bonding permanently to it. Avery's earliest products used waxed paper as the release carrier — serviceable, but thermally unstable, inconsistent in release, and prone to contaminating the adhesive with wax migration.

The substrate problem would not be solved by paper chemistry. It would be solved by silicone. Eugene G. Rochow, a chemist at General Electric's research laboratory in Schenectady, discovered in 1940 that elemental silicon would react directly with methyl chloride in the presence of a copper catalyst to produce methylchlorosilanes — the foundational monomers for industrial silicone production. Rochow filed US Patent 2,380,995 in 1941 (granted 1945); the same chemistry was discovered independently in Germany by Richard Müller that year, and is known today as the Müller-Rochow direct process. Before Rochow, organosilicon compounds were laboratory curiosities produced by Grignard reactions at milligram scale. After Rochow, silicone polymers became an industrial reality.

Dow Corning, founded in 1943 as a joint venture between Dow Chemical and Corning Glass, scaled PDMS production through the 1940s and 1950s. By the mid-1950s, Dow Corning and GE were selling silicone release coatings for paper. The match with Avery's self-adhesive label was definitional: a platinum-cured silicone film on glassine gave the first reliably consistent, thermally stable, clean-release PSA carrier. Through the 1960s the combination scaled globally; Avery merged with Dennison Manufacturing in 1990 to form Avery Dennison.

The European self-adhesive-label federation FINAT — founded in 1956 in Paris — standardised release-paper construction, release-force testing, and terminology across the continent. FINAT FTM-5 remains the reference release-force test method globally. The 1973 adoption of the UPC barcode in US supermarkets, and the logistics-label explosion led by FedEx and UPS through the 1980s, pushed release paper into mass-scale specialty production. The 2010s and 2020s, dominated by e-commerce shipping labels and thermal-transfer growth, turned it into the quiet high-growth grade it remains today.

A consequential concern has accumulated: release paper is, by design, waste. The substrate's job ends the moment the label is peeled. Historically it went to landfill. Recent programmes — Cycle4Green, UPM Raflatac's RafCycle, and Ahlstrom's Liner Loop — collect spent release paper from high-volume label converters back into new paper products. Ahlstrom-Munksjö introduced the first commercially viable recycled-content release paper in 2019; Mondi now runs take-back programmes across European converter sites.

How it's made

Release paper is a composite: a carefully engineered base paper with a thin, cured silicone elastomer film on one or both sides. The base does most of the mechanical work; the silicone does all of the release work.

The base paper sits in one of four families. Glassine, a super-calendered, hydrated, translucent sheet running 35–90 g/m², is the dominant thin-carrier base — its dense, almost glass-like surface resists silicone strike-through and gives the final release paper excellent printability and thinness. Super-calendered kraft (SCK) — unbleached or semi-bleached kraft passed through a super-calender stack — is used where more carrier stiffness and tear resistance are needed, particularly for shipping and industrial labels. The underlying sheet character is close to machine-glazed greaseproof WPI-g-000904, super-densified by calendering rather than hydrated by refining. Clay-coated kraft (CCK) provides a cheaper, coated base for less demanding applications. Polyethylene-extrusion-coated paper is used where moisture resistance or dimensional stability under high humidity matters — medical adhesives and some high-speed label lines specify it.

The silicone coating itself is a polydimethylsiloxane (PDMS) system. In modern practice it runs as a three-component formulation: vinyl-functional PDMS as the base polymer, hydride-functional PDMS as the cross-linker, and a platinum complex — Karstedt's catalyst — as the curing agent. A release modifier, typically a higher-molecular-weight methyl-phenyl or branched silicone, is added to tune the release force up or down. The formulation is applied to the base paper by reverse-gravure roll, slot-die, or (historically) air-knife coater, laid down at a nominal 1.0 g/m² dry (commercial range 0.8–1.5 g/m²). The web then passes through an impingement oven at 120–180 °C, where platinum-catalysed hydrosilylation cures the silicone into an insoluble, rubbery three-dimensional network in 5–15 seconds of dwell time.

The solvent question has been central to the chemistry's evolution. Early silicone release coatings, through the 1970s, were applied from toluene or xylene solutions — effective but environmentally burdensome. Modern production is dominated by 100% solventless (high-solids PDMS applied neat) and increasingly by UV-cured or electron-beam-cured silicone systems, which eliminate thermal oven energy entirely. Machine speeds run 400–1,200 m/min on modern silicone coaters, with line widths to 2.6 metres.

Specs that distinguish it

The contractual numbers for a release paper spec sheet are unusual because most of them measure the chemistry of not sticking, not the paper:

• Basis weight — 50–150 g/m² for the full coated construction, depending on base-paper family. Thin label carriers run 55–65 g/m²; shipping and heavy-industrial grades step up to 100–150.
• Silicone coat weight — 0.8–1.5 g/m² dry, measured by FINAT coat-weight test or by X-ray fluorescence on silicon. The headline chemistry spec.
• Release force — 5–80 cN/inch, measured by FINAT FTM-5 at 300 mm/min using Tesa 7475 reference tape. Low values (5–15 cN/inch) are "easy release"; medium (15–40) is the standard label range; high (40–80) is "tight release" for narrow-web high-speed dispensing.
• Subsequent adhesion (SA) — ≥ 70% of the adhesive's control bond strength after contact with the release paper. The test that catches silicone migration into the adhesive. Below 70%, the label will fail to stick to its intended surface after dispensing.
• Bekk smoothness — 400–1,200 s on glassine bases; 200–500 s on SCK. Surface smoothness affects both silicone lay-down and the uniformity of release force across the web.
• Dimensional stability (20–80% RH) — < 0.15% change in either machine or cross direction. High-speed automated label dispensers will jam if the carrier swells or shrinks asymmetrically under ambient humidity change.

Variants and family

Release paper splits first by base-paper substrate and second by release chemistry:

• Glassine release paper — the dominant substrate for thin, flexible, and translucent label carriers. Low basis weight (55–85 g/m²), high density, excellent silicone holdout. The workhorse.
• SCK (super-calendered kraft) release paper — heavier, opaque, stronger. Used for shipping labels, automotive graphics, and industrial decals that need carrier stiffness through the label application.
• CCK (clay-coated kraft) release paper — cost-optimised for less demanding applications; a pre-applied clay coating reduces silicone anchorage requirements.
• PE-coated release paper — polyethylene-extrusion-coated base plus silicone, for moisture barriers and medical adhesives where humidity exposure during storage or application would otherwise distort a paper-only carrier.
• Dual-sided release paper — silicone-coated on both sides with differential release forces, used for interleaved label constructions and transfer-tape applications.
• Tight-, standard-, and easy-release grades — the same base and silicone chemistry, different release modifiers, tuned for specific adhesive and dispenser combinations.

The closest chemical cousin outside the label industry is baking parchment WPI-g-000649 — also a silicone-coated paper, but engineered for high-temperature food-contact release rather than low-adhesion PSA release. The two grades look similar at a glance and share an ancestor in silicone-coated greaseproof WPI-g-000904, but the chemistry targets and regulatory baselines are different:

Buying notes

Three red flags for buyers and quality engineers auditing release-paper supply:

Release-force drift batch-to-batch. The single most disruptive defect. Automated label dispensers are calibrated to a specific release force; a 15–20% swing between reels will cause either label mis-feeds (release too tight, label fails to peel) or flag-off errors (release too loose, label peels prematurely). Demand batch release-force certification on every delivery, not a typical value. Low coefficient of variation (< 10% within a reel) is as important as the absolute figure.

Silicone migration to adhesive. The test here is SA — subsequent adhesion — not release force. If the release paper's silicone is under-cured (insufficient platinum catalyst, incomplete hydrosilylation, oven underperformance) or contains extractable low-MW silicone fractions, silicone molecules will migrate into the PSA during storage. The adhesive then carries a silicone film of its own and fails to bond to its target surface. The failure mode shows up weeks after dispensing, making field root-cause diagnosis painful. Always specify SA ≥ 70% as a contract clause, not a typical value.

Static generation at high-speed release. Release is an act of charge separation; at 30,000 labels per hour on a narrow-web line, release paper can accumulate several kilovolts of static charge on the web. That static causes misfeeds, ignites solvents in nearby pressrooms, and damages electronics. Anti-static treatment (conductive additives in the silicone or a corona treatment on the base paper) is standard for high-speed grades; confirm it is specified.

On sustainability: FSC Mix is the baseline for mainstream release paper; FSC 100% is available from European mills at a modest premium. Recycled-content release paper — Mondi's recycled-content lines and Ahlstrom's Liner Loop products — now covers a growing share of the specification market and is the direction brand owners with sustainability commitments are pushing.

Related reading

• Glassine paper — the dominant base-paper substrate for thin-carrier release-paper construction, and a grade with its own identity outside the release market.
• Baking parchment paper — the silicone-coated food-contact cousin; shares the PDMS chemistry but targets thermal release rather than PSA release.
• Pressure-sensitive adhesive — the adhesive class that release paper exists to carry; understanding PSA rheology is prerequisite to understanding why release-force specs are so tight.
• Silicone coating — the PDMS chemistry, platinum-catalysed hydrosilylation, and solventless vs UV-cure process distinctions.