Tamper-evident seals and security labels: VOID, fragile paper, holograms and serialised 2D codes

1. Four products that solve four different problems

"Security sticker" is used for all of these in enquiries, yet the mechanisms are unrelated. Choose the wrong one and the money buys nothing.

In practice the workhorse is a combination: fragile paper or VOID as the base, a serial QR printed on top. That gives you "cannot be removed" and "can be checked" in one label.

2. VOID: what it can leave behind, and how to stick it

The construction is three layers: face stock, release coat, adhesive. Intact, it holds as one piece. Peel it and the adhesive stays on the surface while the face leaves with the split coating, so the word VOID appears on the box — a physical result, not printed artwork.

• The wording is specified. Beyond VOID you can have a brand name, a bilingual warning or a running number. Finer letterforms demand tighter material and die precision, and they blur on rough surfaces.
• Legibility starts with the substrate. Glass, PET bottles, laminated cartons and UV-coated board show the word clearly. Rough board, recycled board, wood and textiles absorb adhesive and leave a faint or invisible mark: switch to a high-tack adhesive, add a primer, or use fragile paper instead — but always prove it on a sample, never on assumption.
• Final adhesion is reached after about 24 hours. Initial tack and final bond are different numbers. A sample that peels off easily an hour after application may simply be uncured; conversely, on low-surface-energy PP or PE the edge may still lift after a day.
• Adhesive choice: a standard permanent acrylic covers most work; rough board, low-energy plastics and chilled or frozen conditions need high-tack or low-temperature grades. Never use removable adhesive for tamper evidence — removable is designed to come off cleanly.
• Application matters. Where the seal crosses a fold between lid and body, press and then roll for 3–5 seconds; a roller beats a thumb; do not stack heavy cartons on freshly sealed boxes for the first 24 hours.
• Storage: 23 ± 2 °C and 50 ± 5 % RH, sealed and out of sunlight. Months in heat and humidity and the adhesive migrates into the liner; the applicator then misfeeds.

3. Fragile paper or VOID: leave a trace, or refuse to come off?

You can laminate the two if you genuinely need both, but the price rises and so does the caliper, which makes application harder. Most projects need one of them: ask whether the requirement is to see that it was opened or to stop the label being moved intact.

4. Holograms: stock versus bespoke, and when bespoke pays

Holograms are embossed, not printed: the pattern is a microstructure pressed from a nickel master. That is why changing the artwork means making a new master.

• Stock patterns: geometric, starburst and generic lettering designs are held by several suppliers — no origination charge, low unit cost, but no exclusivity. Anyone can buy the same pattern.
• Bespoke: a new master is originated, charged once. It only amortises on meaningful volume, and makes sense where the brand is already being copied.
• Interaction with print: holographic areas reflect light, so never place a barcode or 2D code on top of one — scanners will fail. Registration between the foil and four-colour print needs tolerance, or the pattern looks muddy.
• Positioning: a hologram raises the barrier, it does not make copying impossible. What actually stops counterfeiters is the serial number plus lookup: when the same code is scanned a second time, the buyer can be told it has already been used.

5. Seal labels: sizing the bridge and choosing the adhesive

A seal works by bridging — gripping both lid and body so the box cannot be opened without destroying it. So the size is not arbitrary:

• Bridge length: 15–20 mm on the lid and 15–20 mm on the body, typically 30–40 mm total as a minimum. Too short and the whole seal lifts off without a trace; too long and it fights the curve of the box.
• Width: 12–20 mm is the common range. Under 10 mm there is not enough tensile strength; over 25 mm looks heavy on small cartons.
• Adhesive and surface: laminated and UV-coated cartons and rough corrugated need a heavier coat or a different adhesive. A silicone-treated surface will not hold anything — check whether the box has been anti-stick treated.
• Placement: clear of barcodes, opening arrows and the brand's main graphic; keep multi-panel sealing consistent, or consumers read the difference as tampering.
• Tear slit: whether to add one depends on how the end user opens the pack — a tear slit suits e-commerce, a solid seal suits gift packaging.

6. Serialisation and GS1 2D codes: write the spec, or it will not scan

There are three common serial formats: ① a plain serial URL on your own domain ② GS1 Digital Link (the GTIN inside the URL) ③ GS1 DataMatrix (pharma, industrial, internal logistics). The choice depends on who scans it — a consumer's phone, a retail checkout, or a warehouse.

If the goods go through a retail checkout, the specification comes from the GS1 General Specifications, not from what looks clear on screen:

What "Sunrise 2027" is and is not: it is an industry goal set by GS1 and retailers — that retail point-of-sale systems will be able to read those three 2D symbologies by the end of 2027. It is not a regulation and not a sunset date for the EAN barcode; no brand is obliged to drop linear barcodes on a given day, and during the transition a 2D code is added, never substituted. Individual retailers may set their own requirements, so the useful question is what your channel asks for, not what the calendar says.

The printing reality: a QR with modules under 0.4 mm needs tight control of dot gain and registration on flexo and offset, and reaching grade 1.5 requires test prints and measurement. Variable serials are best run digital or inkjet, with encoding rules, error-correction level (L/M/Q/H), quiet zone and human-readable text all settled before plating. Do not accept "my phone reads it" as the test — phones are forgiving, checkout scanners are not.

7. What you are actually paying for

1. Material: VOID film, fragile paper, holographic film — grammage and adhesive grade can double or triple the cost.
2. Tooling: custom VOID wording, bespoke hologram origination and the die for a shaped seal are all one-off charges.
3. Variable data: serials are billed per label (or per code), plus verification and data delivery.
4. Print and finishing: colours, foil, spot UV, die-cutting, slitting, rewinding.
5. Quantity: one-off costs spread over the run, so smaller runs cost more per label. That is arithmetic, not a markup.

The pragmatic small-run route: stock material, digital variable data, standard wording — skip bespoke holograms and shaped dies, and put the budget into serials and the lookup. Upgrade to bespoke once volume is stable and copies actually appear.

8. Seven things to send with the order, five to check on delivery

Send these seven:

1. Application and substrate: carton, laminated board, plastic or glass; flat or curved; any UV or anti-stick treatment.
2. Size and placement: length by width, which two panels are bridged, how many positions.
3. Type: VOID, fragile paper, hologram, serial code, or a combination.
4. Whether the wording or logo is custom (send vector artwork).
5. Serial rules and quantity: symbology, error-correction level, GS1 Digital Link or not, uniqueness, whether a data file is returned.
6. Adhesive: ambient, chilled or high-tack; any frozen or outdoor conditions.
7. Delivery and packing: rolls or sheets, core diameter, labels per roll. Proofs take about 24 hours, small runs about one week, bulk about 15 days.

Check these five:

1. Peel after 24 hours, not immediately: is the wording legible, did the adhesive transfer cleanly, any stringing?
2. Conditioning: heat and humidity, then cold; watch edge lift and how the wording changes.
3. Scanning: a phone and a dedicated scanner, plus ISO/IEC 15415 grading — not just "it opens".
4. Serials: sample for duplicates and sequence gaps, and reconcile the data file against the physical labels.
5. Fit: apply to the actual box and look for edge lift, or a seal that covers the barcode or the opening arrow.

Related reading: Why barcodes fail to scan, Specifying roll labels, Ordering from China: shipping and terms, Export carton marking and ITF-14, Overstickers for Hong Kong retail.