What a peel test actually measures

ASTM F88/F88M is the underlying method behind the seal-strength numbers EN 868-5 sets — 1.5 N per 15 mm for steam sterilization processes, 1.2 N per 15 mm for other processes. The test itself is mechanical and specific: a strip of the sealed pouch, cut to a fixed width, is clamped on both sides of the seal and pulled apart at a controlled, steady speed on a tensile tester. The instrument records the peak force required to separate the two layers, and that peak — not an average, not a pass/fail visual judgment — is the number compared against the standard’s minimum.

That specificity is also the test’s limitation for day-to-day use: F88 needs a calibrated tensile tester, a cut sample, and destroys the pouch in the process. It’s the method a manufacturer runs during product validation and periodic quality control, not something a CSSD or clinic runs on every pouch coming off a sealer.

What’s actually available at the point of packing

Between manufacturer-level peel testing and a device leaving in a compromised pouch sits a set of non-destructive checks that a technician can realistically apply to every seal:

  • Visual inspection of the seal line — looking for channels (gaps where the two layers didn’t fully bond), wrinkles, or areas where the seal narrows or disappears. A continuous, uniform seal line across the full width is the baseline check.
  • Seal width consistency — a heat-sealer set to the correct parameters produces a seal of consistent width along its whole length; a narrowing or tapering width can indicate the pouch shifted during sealing or the sealer’s pressure isn’t even.
  • Tactile check of the print-change indicator, where present — many pouches print a process indicator that changes appearance once exposed to the sterilization parameters, which confirms exposure but is a separate signal from seal mechanical strength, not a substitute for it.
  • Checking for scorching or under-sealing on a heat-sealed pouch — a seal line that’s visibly discolored or brittle suggests the sealer ran hot or dwelled too long; a seal that separates with light finger pressure suggests the opposite.

None of these checks produce a force-in-newtons number the way F88 does. What they do is catch the failure modes most likely to occur at the point of use — a distracted pass through a sealer, a sealer drifting out of calibration between scheduled checks — before a compromised pack reaches storage.

Why the two levels of checking aren’t redundant

The peel test’s job is validating that a pouch material and sealing process, used correctly, can meet the EN 868-5 minimum in the first place — that’s a property of the packaging system and the sealing parameters, established once and periodically re-verified. The point-of-packing visual and tactile checks have a different job: catching whether this specific pouch, right now, was actually sealed the way the validated process assumes it will be.

A pouch material that passed F88 testing in the manufacturer’s validation doesn’t stay validated if the sealer used to close it has drifted out of its own calibration, or if a pouch was folded over before sealing and never fully closed. Point-of-packing inspection is what catches that gap — not by re-measuring seal strength, but by looking for the visible and tactile signs that a seal didn’t form the way it should have.

What this means for a CSSD’s routine

  • Seal integrity checking belongs at the pouch-closing step, every pouch, every time — it’s fast, non-destructive, and catches the failures most likely to actually occur day to day.
  • Formal peel testing (or trusting a manufacturer’s F88 data) belongs at the packaging-system validation level — confirming a pouch material and sealer combination, correctly used, can meet the standard — not at the routine packing bench.
  • A sealer’s own periodic verification — checking its temperature and dwell-time settings are still within the manufacturer’s specified range — sits between the two, and is what keeps the point-of-packing visual checks meaningful rather than a check against a machine that’s already drifted.