The 60-second answer
- Do not start by changing the adhesive. The four usual causes of edge lift, bubbling and wrinkling are low surface energy, a contaminated surface, a mismatch between curvature and facestock stiffness, and simply not giving the adhesive time to wet out. A "stronger" adhesive rarely helps: on a surface it cannot wet, an aggressive adhesive fails the same way.
- Sort by when it appears. Visible immediately: trapped air or application angle. Lifting after 24-72 hours: no wet-out, or stress being released. Growing over days: container outgassing (freshly moulded PET/HDPE releases gas for 24-48 hours). Tunnels already on the roll before labelling: web tension — nothing to do with the applicator.
- Then look at which layer the bond failed at. This is the fastest diagnosis. Container comes away clean: the adhesive never bonded (surface energy or contamination). Adhesive left on the container: anchorage to the facestock failed (change the construction, not the adhesive family). Adhesive split, residue on both sides: cohesive failure (over-temperature, overload, creep under sustained stress).
- 36 mN/m (36 dyne/cm) is the reference line. PP and PE typically sit at 29-34 and need an LSE adhesive; PET 41-44, PVC 39-41, ABS around 42, clean glass above 46 are easier. Corona treatment decays with time, so "it was treated at the factory" is not the same as "it is treated now".
- Apply at 21-38 C, never below 10 C. Then leave 24 hours at ambient (72 in bad cases) before cold chain, container loading or rain — and judge acceptance at that point, not at the end of the line.
1. Triage first: when it appears tells you where to look
The same "label will not stay down" has completely different causes depending on timing. This table is the fastest step on the floor: ask when it was first seen, then read across.
| What you see | When it appears | Most likely cause | Check first |
|---|---|---|---|
| Small scattered bubbles | Immediately | Trapped air — the roller, brush or pad is not pushing air out from the leading edge | Wipe-down condition and pressure, label-to-container angle, line speed |
| Bubbles that grow, or appear overnight | Hours to days | Container outgassing: freshly blow-moulded HDPE/PET keeps releasing gas, sealed in by an impermeable film | Label one fresh container and one that has stood two days — fastest confirmation |
| Fine, uniform micro-bubbles under clear film | Immediately, usually gone within 24 h | Poor wet-out: the adhesive has not flowed into full contact, worse where surface energy varies | Try another roll from the same batch, add pressure, re-check after 24 hours |
| Edge or corner lift, especially on cylinders and tapers | After 24-72 hours | No wet-out / curvature-stiffness mismatch / adhesive ooze at the die-cut edge | Which layer failed (section 3), container diameter, facestock thickness |
| Creases in the facestock itself | Immediately | Facestock too stiff for a compound curve, or stretched during application | Softer/thinner face (soft PP/PE film), adjust infeed angle and tension |
| Straight raised channels (tunnelling) | Already on the roll, before labelling | Web tension, liner taking up moisture, film face relaxing after slitting | Unwind three outer wraps of a fresh roll; return the roll with its storage conditions |
| Only in cold weather | Cold season | Cold application: adhesive too firm, low initial tack; static attracting dust on film | Line temperature and the container surface temperature, not the room air |
One practical rule: "it looked fine coming off the line" is not an acceptance test. A pressure-sensitive bond is a wetting process, not an instant. What it looks like after 24 hours is the real result — so mark the time on the batch and check the same batch the next day.
2. Four defects, four different owners
| Defect | Definition | Typical appearance | Usually the responsibility of |
|---|---|---|---|
| Edge lift / flagging | The edge separates while the centre still holds | Corners or a whole edge curling, often with a clean container surface underneath | Surface energy and contamination, application temperature, facestock stiffness, adhesive ooze at die cuts |
| Bubble / blister | Air or gas trapped under the label | Rounded pockets that move under finger pressure and spring back | Wipe-down, container outgassing, poor wet-out |
| Wrinkle | A crease in the facestock itself; the adhesive is usually still bonded | Diagonal creases, or radial creases across a curve | Facestock stiffness against the container shape, stretching at application |
| Tunnelling | The facestock separates from the adhesive (or the liner), forming a raised channel | Straight, parallel to the machine direction; visible as soon as the roll is opened | Web tension in converting/slitting, moisture in the liner, storage conditions |
Why the distinction pays: tunnelling is a roll problem, bubbles are an application problem, edge lift is a surface-and-adhesive problem, wrinkles are a stiffness problem. Review them together and you end up with "try another adhesive", which fixes none of them.
3. Edge lift: which layer did the bond fail at?
Peel a label off and see where the adhesive stayed. No instruments needed, five seconds, and it points straight at the process to change.
| What you find | Failure location | What it means | Change first |
|---|---|---|---|
| Container perfectly clean, full adhesive layer on the label | Adhesive / substrate interface | Wetting failure: surface energy too low, contamination (mould release, silicone, dust, oil), or application too cold | Clean (isopropanol), measure dyne level, specify an LSE adhesive, raise application temperature |
| Adhesive left on the container, label back is bare | Adhesive / facestock interface | Anchorage failure: the adhesive cannot grip the face material, common on untreated film face stocks | Change the construction (face plus adhesive), not to a "stickier" grade of the same family |
| Residue on both sides, adhesive split down the middle | Cohesive failure within the adhesive | Load beyond the adhesive's internal strength: sustained stress, service temperature too high, permanent pull on a curve | Higher shear adhesive; reduce curvature stress with a softer face material |
Three different prescriptions, so peeling one label beats any amount of guessing. One common misread: a batch applied in winter lifts much more, and it is usually not a bad batch — the adhesive was simply too firm to wet out. When the weather warms up the same labels look "fine" again; that is stress releasing, not proof you applied them correctly.
4. Surface energy: the 36 mN/m line, and the materials table
A pressure-sensitive adhesive has to flow out to bond. Below a certain surface energy it only makes partial contact: the label looks applied and separates along the edges days later. The industry reference threshold is 36 mN/m (36 dyne/cm) — below that the material is low surface energy (LSE) and needs a dedicated adhesive.
| Substrate | Typical surface energy (mN/m) | Difficulty | Note |
|---|---|---|---|
| PP (polypropylene) | 29-31 | Hard (LSE) | Bottles, caps, tubes; LSE adhesive required |
| PE (polyethylene) | 30-31 | Hard (LSE) | HDPE bottles; outgasses after blow moulding, see section 5 |
| PS (polystyrene) | 33-35 | Hard-ish | Close to the threshold; always run an application test |
| PVC | 39-41 | Moderate | Common for labels and shrink sleeves |
| PET | 41-44 | Moderate to good | Clear bottles; cleanliness matters a lot |
| ABS | about 42 | Good | Standard permanent adhesive is usually fine |
| Glass (clean) | 46 and above | Good | Often carries mould oil or silicone — cleaning is the deciding step |
| Silicone / release-coated | 20-24 | Practically unbondable | Change material or mask the area; no adhesive solves silicone |
Three things that matter in practice:
- These are typical ranges, not specifications. Grade and additives move a material several mN/m. To decide, measure: a dyne pen (the wetting-tension test behind ASTM D2578) drawn across the surface — if the line does not bead up within two seconds, the surface is at or above that value.
- Corona treatment decays. PP and PE rely on corona discharge to raise surface energy, and the effect falls off with time, heat and handling. "Treated at the factory" does not mean 38 six weeks later — re-test containers that have been in store.
- Printing and labelling want different numbers. Film printing generally needs at least 38 mN/m to be reliable; the labelling threshold is 36. If the ink will not anchor either, the problem is the material, not the adhesive.
5. Bubbles: three sources, three different fixes
| Source | How to recognise it | Why it happens | Fix |
|---|---|---|---|
| Trapped air | Immediately, varied sizes, random positions | The wipe-down does not push air out from the leading edge; worn brushes, uneven pressure, wrong angle, high line speed | Set the roller or brush, work from the leading edge outwards, slow down; for hand application use the hinge method |
| Container outgassing | Hours to days later, grows, often on thicker sections | Freshly blow-moulded PET/HDPE containers release gas for 24-48 hours after moulding; an impermeable film seals it in | Let containers rest 24-48 hours before labelling, or use a more permeable or micro-perforated face |
| Poor wet-out | Fine uniform micro-bubbles under clear film, looks like the adhesive pattern | The adhesive has not yet flowed into full contact; worse where surface energy varies | Usually clears within 24 hours; pressure, warmer application and better cleaning speed it up |
The second one is the most misdiagnosed. "Yesterday they were perfect, today they are all blistered" is almost always outgassing — nothing to do with the applicator or the adhesive, and no adhesive change will fix it. Let the containers rest, or move to a permeable face. Labelling one fresh container and one that has stood 48 hours settles it in half a day.
Also worth knowing: paper face stocks breathe, film face stocks do not. The same container can be fine with a paper label and bubble everywhere with a clear film. That is physics, not a bad film. If you need clarity and want to avoid outgassing blisters, ask your supplier about micro-perforated or permeable clear films.
6. Wrinkles and tunnels: stiffness, compound curves and web tension
Wrinkles are the facestock creasing. A label applied to a cylinder is fine; on a taper, a shoulder or a compound curve the flat material cannot follow both curvatures at once. Three ways out: a softer, thinner face (soft PP/PE film rather than heavy paper), a smaller label placed on the flatter part of the container, or a genuinely stretchable film.
Tunnels exist before labelling. Face, adhesive and liner react differently to temperature and humidity: a liner takes up moisture and grows, a film face relaxes after slitting, uneven rewind tension stretches one layer more than another. The result is a straight raised channel on the roll that will not press flat. Do not adjust the machine — send the roll back with its storage conditions; the converter can trace the slitting run, whereas you adjusting the applicator just takes on the blame.
The check is simple: open a fresh roll and look at the outer three wraps. No channels — the problem is at application. Channels — the problem is the roll.
7. Six application settings
| Setting | Target | Why | How to check |
|---|---|---|---|
| Ambient temperature | 21-38 C; not below 10 C | Cold adhesive is too firm to wet out; the label holds on very weak initial tack only | Thermo-hygrometer at the line, logged at start-up |
| Container surface temperature | Close to ambient; wait after moulding or cold storage | Surface temperature decides the outcome more than room temperature does | Infrared thermometer on the bottle, not the room air |
| Surface cleanliness | Dry, free of oil, dust and release agents | A pressure-sensitive bond is contact area; oil and dust take contact area away | Isopropanol wipe where needed, fully flashed off before labelling |
| Wipe-down | Roller, brush or pad, leading edge outwards | Pressure expels air and pushes adhesive into surface micro-texture | Check roller hardness and wear, watch the edges |
| Line speed | Slower rather than faster; trial a batch slowly before speeding up | Fast application traps air and leaves no time for wet-out | Run the same batch at two speeds and compare |
| Settling time | 24 hours at ambient, up to 72 | Wet-out is a process, not an instant | No cold store, no container, no rain, no rough handling in that window |
8. A 48-hour acceptance card for the inspection bench
| # | Check | Pass criteria |
|---|---|---|
| 1 | At application | No large trapped-air bubbles, no creases; stop and set the machine rather than releasing the batch |
| 2 | Two hours later | No edge lift; look at the two ends of cylindrical containers first |
| 3 | 24 hours later | Micro-bubbles under clear film should have cleared; if still obvious, it is a wet-out problem |
| 4 | 48 hours later | No new or growing bubbles; growing means outgassing, not the adhesive |
| 5 | Peel one label | Residue location tells you which process is at fault (three cases in section 3) |
| 6 | Outer three wraps of the roll | No raised channels; if there are, return the whole roll instead of adjusting the machine |
| 7 | Substrate surface energy | Dyne pen reading of at least 36 mN/m, essential for PP and PE |
| 8 | Temperature log | Application day at or above 10 C, ideally 21-38 C |
9. FAQ
Q1: Can a stronger adhesive fix edge lift?
Usually not. Edge lift is mostly low surface energy or contamination, and no adhesive wets a surface it cannot wet. The order is: measure surface energy, clean, confirm application temperature — and only then change adhesive, to an LSE grade rather than a higher-tack one. High tack with poor wetting often lifts faster.
Q2: Do PP and PE bottles really need a special adhesive?
Yes. PP and PE sit at roughly 29-34 mN/m, below the 36 threshold, so a standard permanent adhesive bonds initially and separates along the edges within days. Specify an LSE adhesive (usually a modified acrylic or a dedicated rubber formulation) and verify: dyne pen on the bottle, then a sample applied and checked after 48 hours.
Q3: Will small bubbles disappear overnight?
Fine, uniform micro-bubbles under clear film (wet-out) usually clear within 24 hours. Bubbles of mixed size in random positions do not — that is trapped air and needs a wipe-down setting. Bubbles that grow do not either — that is outgassing. See section 5.
Q4: How do I tell outgassing from an adhesive problem?
Run a paired test: one freshly moulded container and one that has stood at least 48 hours, same label batch, same environment. Bubbles on the fresh one only means outgassing; bubbles on both means application or adhesive. Half a day of testing beats three adhesive changes.
Q5: Labels lift much more in winter. Has the adhesive gone off?
Usually not. In the cold the adhesive is firm and flows too slowly to wet the surface, so the label holds on weak initial tack only. When it warms up the stress releases and the same labels look "fine" again — an illusion. Raise the line to 21 C or above, let the containers come to temperature, and judge after 24 hours. For the roll itself, see the storage and shelf-life guide.
Q6: Do you test on our actual containers before shipping?
Yes, on request: the same batch applied to 3-5 of your containers, left 48 hours, photographed and reported with the edge and bubble condition plus the room temperature and humidity at application. If your container is PP or PE, or carries a mould release agent, tell us up front and we will specify an LSE adhesive instead of spending a round on samples that cannot work.
Related reading: Roll label storage and shelf life, Label applicator compatibility, Specifying a roll of labels, Labels for chilled and frozen food, Custom shapes and dies, Barcodes that will not scan.
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