Vacuum Metallized Packaging 3 Real-World Use Boundaries: Food / Cosmetics / Electronics — 3 Light-Blocking Rate Gaps for 0.02μm / 0.05μm / 0.1μm Aluminum Layer Thickness
💡 💡 At a Glance
Vacuum metallization VMPET/VMCPP/VMBOPP aluminum layer thicknesses 0.02μm / 0.05μm / 0.1μm correspond to light-blocking rates 60% / 85% / 95%, OTR 5 / 1.5 / 0.5. Clients asking for good light-blocking must be asked 3 things: product category + shelf life + recycling requirements. Printers must distinguish VMPET (total thickness) from aluminum layer thickness when taking orders.
A print shop in Suzhou took an order for 30,000 stand-up chip bags last year. The brand required good light-blocking and visibility of contents. The sales rep quoted VMPET 12μm directly. The finished bags failed the brand's shelf-life test — the chips oxidized and went rancid within 3 weeks. The brand returned 15,000 bags, and the printer realized: VMPET 12μm refers to total film thickness, not aluminum layer thickness; what truly determines light-blocking rate is that 0.05μm aluminum layer.
The print shop owner felt wronged at the time: I don't know vacuum metallization, I'm just a bag printer — that statement might have held before 2010, but not after 2024. VMPET, VMCPP, and VMBOPP now account for over 30% of cosmetic bag, food bag, and electronic bag orders, and print shop owners must understand the correlation between aluminum layer thickness and light-blocking rate. Otherwise, if the client needs 95% light-blocking and you supply material with 60%, you won't get paid.
1. Vacuum Metallization and Aluminum-Plastic Lamination Are Not the Same Thing
Let's clarify the concepts first. In the packaging industry, metallization actually comes in 3 types:
Type 1: Vacuum Metallization (VMPET/VMCPP/VMBOPP)
Aluminum molecules are evaporated under vacuum onto the surface of PET / CPP / BOPP film, forming an aluminum layer 0.02-0.1μm thick. The aluminum layer is extremely thin, barely affecting film flexibility; it is heat-sealable and printable. Features:
- Aluminum layer thickness: 0.02μm (low light-blocking) / 0.05μm (medium light-blocking) / 0.1μm (high light-blocking)
- Light-blocking rate: 60% / 85% / 95%
- Oxygen Transmission Rate (OTR): 5 / 1.5 / 0.5 cm³/m²·24h·atm
- Recyclable pathway: Can enter the plastic recycling chain (PE/PP/PET respective channels); the aluminum layer is identified as metallized plastic during sorting and processed separately
Type 2: Aluminum-Plastic Lamination (AL/PE, AL/PET)
7-9μm thick aluminum foil (not metallization, but real aluminum foil) is laminated with plastic film adhesive. The aluminum is a continuous foil, not heat-sealable, typically used as a middle layer. Features:
- Aluminum layer thickness: 7-9μm (continuous aluminum foil)
- Light-blocking rate: 100%
- Oxygen Transmission Rate: <0.1 cm³/m²·24h·atm
- Recyclable pathway: Hard to recycle — after aluminum foil and plastic adhesive are laminated, they can basically only be incinerated or landfilled
Type 3: Transfer Metallization
Aluminum is first metallized on a carrier film, then transferred with adhesive onto BOPP/CPP surface, with the aluminum layer remaining on the surface without peeling off. This process achieves a high-gloss metallic feel, commonly used for cigarette cartons, wine boxes, and cosmetic gift box decoration.
The first thing a print shop owner should do when receiving an order is ask the client whether they need vacuum metallization or aluminum-plastic lamination — the price differs by 2-3x and performance by 5-10x. Clients asking for high-end light-blocking typically want aluminum-plastic lamination; clients asking for economical light-blocking typically want vacuum metallization.
2. 3 Scenarios for 0.02 / 0.05 / 0.1μm Aluminum Layer Thickness
This is the comparison table print shop owners really need to see:
| Aluminum Layer Thickness | Light-Blocking Rate | OTR (cm³/m²·24h) | Typical Orders | Price per Ton |
|---|---|---|---|---|
| 0.02μm | 60% | 5 | Biscuit bags, bread bags, short-term puffed food | 18,000-22,000 RMB |
| 0.05μm | 85% | 1.5 | Cosmetic bags, chip bags, coffee bags | 25,000-30,000 RMB |
| 0.1μm | 95% | 0.5 | Pharmaceutical bags, anti-static electronic bags, milk powder bags | 35,000-42,000 RMB |
The root cause of the Suzhou print shop's failure: chip bags require light-blocking ≥85% (otherwise oxidation within 3 weeks), but the VMPET they used had a 0.02μm aluminum layer (60% light-blocking) with OTR 5 — chip oxidation was inevitable. After switching to 0.05μm aluminum layer, OTR dropped to 1.5, and shelf life extended to over 12 weeks.
3. 3 Common Traps for Print Shops
Trap 1: Confusing Total Thickness with Aluminum Layer Thickness
VMPET 12μm means the PET film total thickness is 12μm, of which the aluminum layer only accounts for 0.02-0.1μm. If a print shop owner quotes based on VMPET 12μm and the client requires 95% light-blocking, the printer is digging a hole for itself.
Real case: A print shop in Jiangsu quoted VMPET 12μm for a client's face mask bags in 2023, but the actual aluminum layer was only 0.02μm with 60% light-blocking — active ingredients in the masks (retinol, niacinamide) decomposed under light, and consumers complained of no effect within 3 months. The brand claimed 180,000 RMB in compensation, and the printer paid 60,000 RMB.
Trap 2: Metallized Side Facing Out vs. In
The aluminum layer of VMPET is typically on the PET side. If the printer doesn't specify during lamination, the finished product may end up with the aluminum layer facing out, preventing printing ink from adhering — the printer thinks they printed it, but the ink is actually on top of the aluminum layer and peels off with tape. Correct practice: the aluminum layer must face inward (bonded to the content side), with the print side facing out.
Real case: A print shop in Guangdong had the metallized side reversed in 2024, resulting in the return of 4,000 coffee bags with a direct loss of 8,000 RMB. The print shop owner later said: that day the lamination machine operator shift changed, and the new guy didn't check the material and just ran it.
Trap 3: Wrong Recycling Markings
Metallized plastic (VMPET, VMCPP) is a single material (PET or CPP) and can enter the plastic recycling channel. The recycling mark should be PET 01 or PP 05, not C/PAP 82. If the printer marks it as C/PAP 82 (paper-plastic composite mark), the recycling station will treat it as paper-plastic composite, and truly recyclable plastic will end up in the waste paper pile.
Real data: According to testing data from a Shanghai recycling station in 2024, 23% of VMPET bags had wrong recycling marks — these bags could have been 100% recycled, but with wrong markings they could only be landfilled.
4. 3-Step Judgment When Printers Receive Light-Blocking Orders
- Ask the client's product category: Food (specifically chips/biscuits/coffee) / Cosmetics (serum/face mask/cleanser) / Electronics (anti-static bags/shielding bags). Different categories have different hard requirements for light-blocking rate and OTR
- Ask the client's required shelf life: ≤4 weeks / 4-12 weeks / >12 weeks. Chips, nuts, and coffee beans typically require 6-12 weeks, corresponding to light-blocking ≥85% (0.05μm aluminum layer). Milk powder and pharmaceuticals typically require 24 months, corresponding to light-blocking ≥95% (0.1μm aluminum layer)
- Ask the client's recycling requirements: European and American clients usually require recyclability, corresponding to vacuum metallization (VMPET), not aluminum-plastic lamination (AL/PE). Many domestic clients have no requirements, but e-commerce platforms (JD.com, Tmall) started requiring recycling marks in 2024, and printers must follow regulations
5. 3 Summary Sentences for Print Shop Owners
- VMPET's 12μm is film thickness, not aluminum layer thickness — when the client requests 95% light-blocking, quote 0.1μm aluminum layer, not 12μm total thickness
- Aluminum layer inward, printing outward — confirm aluminum layer position before lamination and run a tape test
- Recycling marks must be based on substrate — VMPET marks PET 01, VMCPP marks PP 05, not C/PAP 82
Practical advice: When a printer receives a metallized bag order, the first document is the brand's product category + shelf life + recycling requirements trio, and the second document is the aluminum layer thickness test report (attached to each roll) provided by the upstream metallized film manufacturer. If these two are incomplete, don't start the machine.
Further Reading
FAQ
How to choose between vacuum metallized VMPET and aluminum-plastic lamination AL/PE?
Consider 3 dimensions: ① Light-blocking requirement — 60-95% use VMPET, 100% must use AL/PE; ② Shelf life — ≤12 weeks use VMPET, >24 months use AL/PE; ③ Recycling requirement — European and American clients must use VMPET (recyclable), clients without recycling requirements can use AL/PE (20% lower cost). The most common trap for print shop owners is when the client says they need 100% light-blocking, you give them AL/PE, but the client also wants recyclability — in this case, you can only return and switch to VMPET 0.1μm (95% light-blocking).
How to verify VMPET's 0.05μm aluminum layer?
Use 4 verification methods: ① Visual inspection — aluminum layer is uniform, no light-transmitting points (characteristic of above 0.1μm); ② XRF (X-ray fluorescence spectrometer) — directly measure aluminum layer thickness, error ±0.005μm, the most reliable detection method for printers; ③ Resistance — 0.05μm aluminum layer surface resistance 1-5Ω/□, 0.02μm aluminum layer surface resistance 10-30Ω/□; ④ Light-blocking rate test — use spectrophotometer to measure transmittance at 400-700nm wavelength. When printers don't have XRF, the resistance method can be used for quick judgment.
What if the ink peels off on metallized bags?
3 causes + 3 remedies: ① Wrong ink selection — ordinary ink adheres poorly on metallized layer, metallized-specific ink or PET-specific ink (such as DIC SP series) must be used; ② Insufficient lamination temperature — metallized bag lamination temperature is usually 80-90℃, ordinary bags only need 70℃, if the printer works at ordinary bag temperature, ink is not fully activated; ③ Aluminum layer oxidation — if stored too long, the aluminum layer oxidizes; use metallized film within 30 days of production, after 30 days ink adhesion drops by over 30%.
Can vacuum metallized bags hold liquid?
Yes, but you must choose the right substrate. Metallized PET (VMPET) cannot directly hold liquid — the aluminum layer will contact the liquid and cause corrosion; VMPET/PE or VMCPP/PE structure must be used, with PE as the heat-seal layer contacting the liquid. Common structure for cosmetic serum bags is PET/VMPET/PE, 3 layers from outside to inside, with liquid contacting PE not the aluminum layer. When printers receive liquid orders, they must confirm which side is the liquid-contact layer during the sampling stage.
How to keep the metallic feel of metallized bags bright?
3 maintenance methods: ① Avoid high temperature and high humidity storage — storage conditions 25℃ ±3 / below 60% RH, above 40℃ aluminum layer accelerates oxidation and darkens; ② Avoid strong acid and alkali contact — acidic ingredients like salicylic acid and fruit acid in cosmetics will corrode the aluminum layer and turn it black; ③ Pre-print treatment — if there is oil on the aluminum layer surface, use corona treatment (38-42 dyne/cm) to improve ink adhesion, metallic feel lasts longer after printing.
Which is more suitable for food bags, VMBOPP or VMPET?
Depends on 2 scenarios: ① Short-term food (bread, biscuits, mooncake gift box inner bags) — use VMBOPP, BOPP has good stiffness and vibrant printing colors, 0.05μm aluminum layer is sufficient, cost is 15-20% lower than VMPET; ② Long-term food (coffee, nuts, tea, chips) — use VMPET, PET barrier property is 3-5 times higher than BOPP, 0.05μm aluminum layer can meet 12-week shelf life. Print shop owners should not mix them when taking orders — if the client wants long-term food and you give them VMBOPP, oxidation and returns will occur within 3 weeks.
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