01Types of blister packs and clamshells
All of these start the same way: a plastic sheet is heated and formed into cavities in a mold. What changes is how the cavity is closed.
- Face-seal blister: the product drops into a clear thermoformed shell, and a printed card is sealed to the shell's flange with heat and pressure. Converters sell it as their entry-level clear pack.
- Full-face seal blister: the plastic covers the whole card face, not just a flange. Converters sell it as more durable and tamper resistant.
- Trapped blister: two pieces of paperboard sandwich the blister's flange. Patents describe it for packs that need more security or structure.
- Hinged clamshell: formed halves hinged along a common edge, then sealed or clipped shut. Two-piece versions exist.
- Tri-fold clamshell: a style converters sell to hang on a wall or sit on a shelf.
- Clamshell with insert card: a printed card sits inside, so you can reprint graphics without touching the mold.
02Pharma blisters and child-resistant rules
Many searchers mean the strip of pills in a medicine box. That build is formed, filled and sealed on one machine, then lidded with foil:
- Push-through: hard aluminum foil you press the tablet through.
- Peel-push: a paper/PET/aluminum lid you peel, then push through. A 2000 Pharmaceutical Technology review said this child-resistant style was used mainly in the US.
- Cold form foil: an OPA/aluminum/PVC laminate pressed into shape without heat. It is a near-total barrier to moisture, light and oxygen, but cavities must be larger and tooling costs more.
The same review said PVDC coated on PVC cuts moisture and gas permeability by a factor of 5 to 10, and PVC laminated with PCTFE had the lowest permeability of the clear films it compared. Honeywell's Aclar films are one PCTFE brand sold for blisters.
Under the Poison Prevention Packaging Act rules (16 CFR part 1700), oral prescription drugs and many OTC products (aspirin, acetaminophen, ibuprofen, iron-containing drugs and supplements, among others) need "special packaging": significantly difficult for children under 5 to open or get a harmful amount from within a reasonable time, and not difficult for normal adults. The numbers in 1700.15 and 1700.20:
- Child panels of 50 children aged 42 to 51 months, up to 4 panels.
- Unit packaging such as blisters needs at least 80% child-resistant effectiveness; a child fails it by opening more than 8 units or enough for serious harm, whichever is lower.
- At least 90% senior adult use effectiveness, on 100 adults aged 50 to 70.
One noncomplying size can be sold if complying packaging is also offered, labeled "This Package for Households Without Young Children."
FDA treats a drug's blister and lid as a container closure system. Its 1999 guidance is still the final version on its site. A draft published August 14, 2026 says that, when final, it will supersede the 1999 guidance; it also covers drugs sold without an approved application, such as OTC monograph drugs, and says postconsumer recycled plastic should not be used in a primary packaging component. Use a packager that already runs drug lines and get the CPSC protocol test report for your exact blister and lid.
03Materials and sealing
| Material | What to know |
|---|---|
| PVC | Thermoforms and RF seals easily; held essentially all of the pharma blister market in 2000; fails APR's North American collection access criteria |
| PET / APET | Common blister and clamshell plastic; generally needs a sealing method other than RF |
| RPET | PET with recycled content; get the percentage in writing |
| PETG | Glycol-modified polyester some converters list for clamshells; ask how it seals and recycles |
| PP | Floats in water, so recyclers can separate it; the 2000 review said it ran slower than PVC on blister machines |
| PVC/PVDC, PVC/PCTFE | Pharma moisture barrier films |
That review measured water vapor transmission (g/m²/day, unformed film) of 1.1 for 10 mil PVC, 2.6 for 10 mil PET, 0.20 for 12 mil PP and 0 for cold form. Dated; ask for current data sheets.
Heat sealing to coated board. The card carries a heat-seal coating on one side, typically polyurethane based and applied by offset printing, per a Smurfit-Stone patent filing. The blister is pressed on with heat. The coating must match board and plastic, so ask which one your converter uses and get a peel test.
RF sealing for clamshells. RF (radio frequency) sealing heats the seam through the plastic's polarity. A Kama of Illinois patent says RF-sealed packages are usually PVC because it seals easily, while PET is much less polar and generally needs another method. Switch a clamshell from PVC to PET and the sealing method may change too. Heat sealing, adhesive, sonic welding and clips are the alternatives converters list.
04Recycling, green claims and food contact
A resin code only identifies the plastic. ASTM D7611 says resin identification codes "are not 'recycle codes,'" and EPA says a code doesn't guarantee the item is recyclable in your area. The FTC Green Guides (16 CFR 260.12) allow an unqualified "recyclable" claim only when facilities are available to at least 60% of consumers or communities where you sell, and any component that significantly limits recycling makes the claim deceptive.
APR says PVC (resin code 3) doesn't meet collection access criteria in North America, and the recycled PET stream is very intolerant of even minute amounts of PVC. APR also rates paper labels and attachments as detrimental, so a card fused to plastic works against you. For sustainable packaging, pick one resin, make the card separable, and qualify the claim.
If a clamshell holds food, every component must be of a purity suitable for its intended use (21 CFR 174.5). PET is covered by 21 CFR 177.1630 and olefins such as PP by 177.1520, under the conditions in each section. Don't call it "FDA approved." Ask for a letter of guaranty naming the sections for your food and temperature. For RPET, FDA reviews recycling processes case by case and gives informal advice on purity, so ask for the recycler's FDA letter.
05Wrap rage, and when to pick each
A sealed clamshell resists theft and tampering, which is why it is hard to open. Amazon launched Frustration-Free Packaging in 2008 to replace "hermetically sealed clamshell cases and plastic-coated steel-wire ties" with boxes that open easily. A decision rule:
- Small, light item on a peg: face-seal blister.
- Heavier item or more theft risk: trapped blister or sealed clamshell, with a tear notch or perforated card you test on real people.
- Graphics change often: clamshell with an insert card.
- Moisture-sensitive tablets: pharma blister with barrier film or cold form foil, from a drug packager.
- Sold mostly online: skip the retail pack; a folding carton or mailer box uses less plastic.
06Tooling, minimums and cost drivers
Custom packs need a thermoform mold, which you pay for and wait for before production. One US thermoformer publishes 8 to 12 weeks from sample approval to first articles for initial tooling. To avoid tooling, some converters sell stock clamshells in hundreds of sizes, or semi-custom programs where you pay only for a mold insert. Ask:
- Tooling price, cavities, and who owns the mold.
- Stock or semi-custom options near your size.
- Minimum per order and per card version. See what MOQ means.
- How price moves with gauge.
- Units per master carton and carton size, for your landed cost.
The Vault lists packaging manufacturers with contacts.
07Before you sign off
- Get a clear, unprinted structural sample with your real product in it before you approve tooling.
- Ask for a peel or seal strength test on the sealed sample, and drop test it in the master carton.
- Measure the gauge at the thinnest point of the formed cavity, not just the flat sheet.
- Write down the resin and recycled percentage and check it in bulk; APR notes PET and PVC thermoforms can be visually confused.
- Matching the pack to the product is covered in the course's packaging lesson in Product Sourcing Secrets.
08How to spec it with a supplier
Write the spec down with a drawing so quotes compare. Our packaging manufacturer list shows suppliers to send it to.
| No. | Field | What to write |
|---|---|---|
| 01 | Structure | Face-seal, full-face, trapped, hinged or tri-fold clamshell, or pharma blister; with drawing |
| 02 | Product | Physical sample, or exact dimensions and weight |
| 03 | Plastic | Resin (PVC, PET, RPET with recycled percentage, PETG, PP), clarity, and gauge before forming |
| 04 | Card | Board type, caliper, heat-seal coating, print colors and finish, hang style |
| 05 | Sealing | Heat seal, RF, ultrasonic or snap; seal width; easy-open feature if any |
| 06 | Barrier | For drugs: film structure and moisture transmission data |
| 07 | Compliance | Food contact letter or child-resistant test report, as relevant |
| 08 | Tooling | Mold quote, cavities, ownership, and lead time to first articles |
| 09 | Packing | Units per master carton, carton size and weight, nesting |
09FAQ
Q01What is a blister pack?
A blister pack is a preformed clear plastic cavity that holds a product against a backing of paperboard, foil or plastic. Retail blisters are sealed to a printed card; pharma blisters hold single doses under foil.
Q02What is the difference between a blister pack and a clamshell?
A blister is a plastic shell sealed or trapped against a separate card. A clamshell is one hinged plastic piece that folds shut around the product, often with a printed card inside.
Q03What are blister packs made of?
Retail blisters are commonly PVC or PET on coated paperboard. Pharma blisters use PVC, often with a PVDC or PCTFE layer, or cold form foil, lidded with aluminum.
Q04Are blister packs recyclable?
It depends on the resin and the card. APR says PVC fails North American collection access criteria and rates paper attachments as detrimental; any "recyclable" claim must meet the FTC Green Guides.
Q05Are blister packs child resistant?
Only if built and tested to be. Under 16 CFR 1700, unit packaging needs at least 80% child-resistant and 90% senior adult use effectiveness.
Q06How are clamshells sealed?
By RF sealing (mostly PVC), heat sealing, adhesive, sonic welding, or mechanical clips and snaps.