Interleaving sheets
Separate adjacent surfaces with a qualified paper, film, or foam while controlling abrasion, contamination, corrosion, and stack loading.
Tags: delivery, packaging, surface-protection
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For stainless steel or glass, Stora Enso specifies smooth, chemically neutral Endura kraft interleaving with controlled impurities. Match the contact surface and damage mechanism before substituting another paper. Stora Enso, Endura Interleaving
Read the actual material specification
The Endura Interleaving technical sheet issued September 2026, replacing January 2026, lists grades of 35, 40, and 50 g/m² with typical thicknesses of 53, 60, and 72 μm respectively. Its test climate is 23°C/50% RH. It distinguishes typical and minimum tensile/tear values and machine direction from cross direction. It also specifies water-extract pH and maximum water-soluble chloride and sulphate contents. Stora Enso, current technical sheet
Basis weight, thickness, directional strength, and chemical limits answer different questions. Preserve the grade and revision; an equal-weight substitute does not establish equal performance on the intended finish.
The same sheet recommends dry, covered, ventilated storage and conditioning toward the production environment before use. Its stated ideal storage conditions are 23°C/50% RH; these are paper-storage guidance, not a universal allowable environment for the packed product. Endura technical sheet
Paper, film, foam, and laminates
| Material family | Useful selection questions | Boundary to preserve |
|---|---|---|
| Purpose-made interleaving paper | Cleanliness, smoothness, strength, moisture, and chemical compatibility | Grammage alone does not establish surface cleanliness or corrosion protection |
| Loose polymer film or film laminate | Contact-side formulation, thickness, slip, puncture, and retention between layers | A separator is not automatically a sealed moisture barrier |
| Thin foam sheet | Surface behavior, thickness, light cushioning, and response under load | Light cushioning does not establish stacking capacity or shock protection for the whole pack |
| Adhesive protective film | Substrate/adhesive match, application, dwell, environment, and removal | Bonded masking differs from a loose interleaf |
| VCI-treated paper | Protected metals, emitting side, enclosure, and process compatibility | Inhibitor performance differs from a plain scratch separator |
Pregis distinguishes interleaving laminates, temporary protective films, protective paper, and edge protection. Its interleaving offering includes film laminated to foam or bubble backing for added padding. Keep the laminate and contact-face specification explicit rather than reducing the choice to “plastic sheet.” Pregis, Surface Protection Solutions
As a foam example, Sealed Air describes Cell-Aire low-density polyethylene foam as non-abrasive surface protection with light cushioning, available in sheets or rolls. It offers anti-static, adhesive, cohesive, and laminated options. Those variants are different purchasing choices; a family-level description does not identify the formulation supplied. Sealed Air, Cell-Aire Surface Protection Foam
Surface compatibility and residue
Define the finished surface being protected: alloy, coating or polish, cure condition, allowable marks, and any subsequent cleaning, painting, coating, or bonding process. For a proposed qualification, examine both the surface immediately after unpacking and its fitness for the next operation. A clean-looking surface and one acceptable for bonding are different acceptance criteria.
Adhesive masking requires a distinct assessment. Presto Tape explains that its acrylic pressure-sensitive protective films are selected through material evaluation, sampling, and customer trials. Its usage guide warns that changes in storage or application conditions can impair performance, and that sunlight or water exposure can contribute to adhesive transfer. Those instructions belong to its protection films, not to every loose polymer separator. Presto Tape, Protection Film Storage and Usage Guide
For a local trial, use actual production finishes and representative contact time, temperature, humidity, and loading. Establish limits for scratches, pressure patterns, gloss/color change, particles, residue, and removal damage where relevant. Inspect both contacting faces. Recheck after material or finish changes rather than assuming a successful trial on one coating transfers to another. This is a proposed qualification approach, not a supplier guarantee.
Moisture and corrosion are separate functions
Cortec's July 20, 2022 technical announcement describes interleaving CorShield VpCI-146 Paper between layers of metal parts inside an outer VpCI-126 film enclosure. The paper supplies inhibitor among the parts; closing the outer package retains it. It distinguishes two-sided inhibitor emission from VpCI-146 from EcoShield VpCI-144's one-sided inhibitor coating and opposite moisture/grease-resistant barrier. Orientation and enclosure are therefore product-specific details. Cortec, Interleaving for Large Bins of Metal Parts
Do not convert this named system into a universal corrosion-free storage period. Determine metal and coating compatibility, initial part condition, exposure, and downstream requirements. Plain paper separation does not supply the same inhibitor mechanism, and an interleaved stack is not necessarily a moisture-controlled enclosure. If the shipment needs dry packaging, define that system separately from its surface separator.
Loading, handling, and package qualification
The separator must remain where contact can occur. In a proposed packing design, define sheet coverage and edge treatment, part orientation, stack height, contact areas, restraints, and how operators insert and remove parts. Check whether sheets fold, migrate, tear, or retain contamination during representative handling. Support and restraint should address the complete load; a soft contact layer cannot be assumed to prevent movement or carry concentrated loads.
Illustrative counting example: a stack of 20 plates has 19 plate-to-plate interfaces. One sheet at each interface needs 19 sheets; adding specified top and bottom sheets gives 21. This arithmetic defines placement only. It does not establish sheet thickness, permissible stack weight, or surface performance. Draw the layer sequence so a supplier and packer interpret the count consistently.
Choose package tests for the distribution environment and define product-damage acceptance criteria before testing. ISTA's guidance treats test selection and product/package acceptance as explicit decisions; where certification is intended, prescribed sequences and conditions apply. A local comparison of two interleaves is useful development work but does not itself establish an ISTA-certified package. ISTA, Getting Started with Design & Testing
Record the selected material, contact side, cut size, placement, storage requirements, reuse criteria if any, and accepted package configuration. Treat an interleaf contaminated with grit, fluids, or damaged material as a changed contact condition requiring assessment, even when the original grade is marketed as reusable.
Related: Delivery guides · Barrier bags · Protective surface films · VCI packaging.