Why stickers peel off, and what helps

The company car comes out of the car wash, and at the back on the left a corner of the lettering is sticking up. Two weeks later the corner has become a strip. This is not bad luck. Stickers peel off, and where they do usually tells you why.

A sticker is like a plaster: on skin covered in cream it will not hold for long. The adhesive feels the same way about wax and grease.

What you read here comes from the vinyl manufacturers' application guidelines. For your particular vinyl, its own data sheet has the final word.

Why do stickers peel off? The corner tells you the cause

First look at where and when the sticker is coming loose:

• Only corners and edges are lifting: according to one manufacturer's troubleshooting table, this is usually down to the installation. Typical causes are edges that were not pressed down firmly enough, stretched vinyl or an untidy cut edge.
• A large part of the area is loose: here the cause often lies in the paint underneath. Either it adheres poorly itself or it had not yet cured.
• Bubbles only appear after a few days: fresh paint and some plastics outgas, even under vinyl that looked perfect on day one.
• The edge lifts after washing: usually it was washed too soon, or brushes and the pressure washer got too close to the edge.
• The sticker did not hold through the winter: applied below 10 °C, adhesion builds up much more slowly, possibly over several days.
• It has held badly from the start: the adhesive does not suit the surface, or there was a film of wax, silicone or cleaner on it.

The surface: wax, silicone and difficult plastics

Vinyl sticks to whatever is on top. If there is a film there, the sticker holds on to the film.

Cleaner residue: cleaning products with wax, oil or moisturising additives such as lotion or silicone leave a film that interferes with adhesion. That includes some glass cleaners and washing-up liquids with moisturisers. Cleaners with nano sealants can also weaken adhesion. Before applying vinyl, that means: no wash programme with wax. Remove grease and oil with a mild solvent such as isopropyl alcohol or the cleaner the vinyl manufacturer specifies, and wipe dry with a second, clean cloth before the liquid evaporates. Isopropyl alcohol is highly flammable: test it on an inconspicuous spot first, ventilate well, no flames or sparks nearby.

Paints with additives: silicones or waxes in the paint, common in anti-graffiti paints, can prevent adhesion from the outset. Powder coating can also contain waxes and counts as low-energy, meaning hard to bond to.

Plastic surfaces: polyethylene and polypropylene are also among the surfaces that are hard to bond to. Only apply vinyl to plastic parts if they are painted or completely smooth and a test application holds. If water beads up on them, the manufacturers advise against applying vinyl.

Plasticisers and rubber: according to adhesive manufacturers, plasticisers from flexible PVC, found in tarpaulins for example, can migrate into the adhesive and weaken adhesion over time, faster in warm conditions. There are special vinyls for lorry tarpaulins. Rubber can also contain plasticisers and oils and needs an adhesion promoter.

Fresh paint: the curing time given by the paint manufacturer is what counts. Air-drying paints need at least a week at room conditions, up to 30 days depending on the paint. Stoving enamels and powder coatings are touch-dry once cooled, but not yet fully cured. Otherwise solvent residue forms gas bubbles under the vinyl. That is why we only apply vinyl to freshly painted and freshly powder-coated parts three weeks after coating, which matches what the vinyl manufacturer requires. Polycarbonate and glass-fibre-reinforced plastic can also outgas, and the bubbles sometimes only show after weeks. A test piece with a heat test reveals this beforehand.

The adhesive does not suit the purpose

A removable adhesive is meant to let go again. For promotions, trade shows and shop windows, that is exactly what you want. Our standard sticker is the opposite. Polymeric vinyl, permanent adhesive, built for outdoor use: it is not meant to let go. If a sticker needs to hold stubbornly on a powder-coated toolbox, the manufacturers recommend a stronger adhesive for difficult surfaces and a test application beforehand.

If your surface is not listed in the vinyl's data sheet, ask us which adhesive suits it.

Installation mistakes: temperature, pressure, stretched vinyl

Many lifting corners are already created during application.

Too cold: the minimum temperature is in the vinyl's data sheet. Below 10 °C it takes considerably longer for the sticker to hold, and it needs more pressure. Put the sticker and the workpiece in the room where you will apply it a few hours beforehand. Afterwards, the surface should stay at that temperature for at least 24 hours before cold or wet weather reaches it.

Edges not pressed down: at the end, the squeegee goes over every edge once more with firm pressure.

Stretched vinyl: vinyl that was pulled over a curve during application wants to return to its flat shape. It shrinks, and the edge lifts. That is why professionals post-heat stretched areas and edges and then squeegee them again. The right temperature is in the vinyl's data sheet and is measured with an infrared thermometer. Keep the heat gun moving all the time and never work with a naked flame. Too much heat can burn the vinyl, some plastics barely tolerate heat, and paint can be damaged. On a vehicle, this is work for a specialist.

Swage lines and rivets: the vinyl is not pulled into sharp-edged swage lines or over rivets; it is cut and applied with an overlap. Peeling from swage lines is especially familiar on delivery vans and box vans. For such surfaces, the manufacturers recommend a specialist.

The cut edge: vinyl that ends flush with the edge of the part can shrink, and the exposed edge takes the full force of car wash brushes and the airstream. A hesitantly cut, frayed edge can be the point where peeling starts.

Before larger jobs, a test application on the real surface is worth it. Check adhesion after 24 hours. If it is too weak, clean again and test once more.

After installation: washing, pressure washers, cleaners

According to the application guidelines, full adhesion is reached after about three days, longer in the cold. Until then, the sponge stays in the bucket.

After that, hand washing is the gentlest. Better avoid brush car washes: if a brush catches a loose edge, it can tear it further. Skip wax programmes. Matte or textured vinyl gets neither wax nor polish. Cutting and polishing compounds have no place on any vinyl.

Pressure washer: ideally not at all. One manufacturer advises against it entirely on vehicles with graphics, another only as a last resort. Too much pressure forces water under the vinyl, and then the edges lift. If you do it anyway, keep at least to these manufacturer values, unless your vinyl's data sheet gives stricter ones: no more than 80 bar, water no hotter than 60 °C, a distance of at least 40 cm, nozzle at right angles to the surface, wide 40-degree flat-jet nozzle. Never spray flat onto the edge.

Cleaners: use mild, non-abrasive products such as pH-neutral car shampoo. Nothing strongly acidic or alkaline, no acetone, no thinners.

After washing, walk round the vehicle once and look at the edges. Loose lettering can peel further while driving and needs to be repaired or removed.

Can you stick a sticker back down?

Only to a limited extent. One manufacturer describes simply pressing it back down only for wall and facade graphics, and itself calls this aggressive, because the surface is likely to be damaged in the process.

For vinyl lettering, one manufacturer describes a different approach. The lifting edge is trimmed back to where the vinyl still adheres firmly, without cutting into the paint. On a vehicle, this is best left to a specialist. The new edge is then secured with a sealing tape in a matching gloss level or with an edge sealer. The sealer can also be applied afterwards to edges that are already lifting, and slows further wear.

Caution: edge sealer contains solvent that attacks some paints, so test it on an inconspicuous spot first. It is flammable: use it away from heat and flames and ventilate well. It is applied from 10 °C onto a clean, dry edge and then left to dry for at least 24 hours, longer in the cold.

Vinyl that has weathered outdoors cannot be restored to its original condition. Then reapplying is the more honest route, piece by piece or completely.

When promotion adhesive ends up on the toolbox

A typical sequence: powder-coated toolboxes are to be given a marking. The stickers used are the same ones with removable adhesive as for a trade show promotion. On day one everything sits well. After a few weeks the corners are lifting, first on the boxes that slide back and forth in the van every day.

The pattern fits: powder coating is hard to bond to and can contain waxes, and on top of that there is abrasion at the edges. On the second attempt, an adhesive for difficult surfaces is chosen and a test application is done on one box first. The surfaces are thoroughly degreased, the edges pressed down firmly, and afterwards the boxes stay in a warm room for a day.

Why reapplying alone is not enough

Our founder has seen lifting corners over more than 30 years in the trade, and since 2017 we have seen them in our own company too. So, without beating about the bush: a lifting sticker usually shows what was not right with the surface, the choice or the installation.

Stick the same material onto the same surface again without looking for the cause, and you will often soon see the same corner. That is why, with our vehicle graphics, we pay particular attention to the edges.

The four factors to check before every order are in Stickers you can't overlook, and service life as a criterion is in Stickers must meet specific requirements. Vinyls for different surfaces: Foil technology.

Conclusion: the corner usually points the way

Where a sticker comes loose usually shows why. Before you reorder, check:

• The surface: paint, powder coating, plastic or tarpaulin?
• Its condition: does water bead up? Has the paint cured?
• The purpose: should the sticker come off again later or last a long time?
• The installation: who applies it, at what temperature, and when is it first washed?

Write to us via Contact and tell us what the sticker is going on and where it is coming loose, and we will advise you on vinyl and adhesive. If you like, our sign-making team can do the installation; more under Services. Custom stickers can be ordered online at koeck-print.at. If an indoor sticker needs to come off again later, or one needs to last a long time on a difficult surface, ask us first. In our free file check we look at your print file before printing.

Frequently asked questions

Why do the corners of my sticker always come loose first?

If only corners and edges are lifting, according to one manufacturer's troubleshooting table it is usually down to the installation, for example edges not pressed down firmly, stretched vinyl or an untidy cut edge. Abrasion, car wash brushes and pressure washers add to it. If a large area comes loose instead, the cause often lies in the paint underneath.

Can I stick a lifting sticker back down?

Only to a limited extent. For vinyl lettering, one manufacturer describes trimming the loose edge back to where it still adheres firmly, without cutting into the paint, and securing it with sealing tape or edge sealer. The sealer contains solvent and is flammable, so test it on the paint first and ventilate well. If the vinyl has already weathered, only reapplying will help.

How long after application can I wash the vehicle?

According to the vinyl manufacturers' application guidelines, full adhesion is reached after about three days, later in the cold. Only wash after that. Hand washing is the gentlest. Avoid brush car washes and wax programmes, and ideally pressure washers altogether. If you must: no more than 80 bar, 60 °C, at least 40 cm distance, never flat onto the edge, unless the vinyl's data sheet specifies otherwise.