How to test the airtightness of cosmetic packaging materials?

The airtightness testing of Cosmetic Packaging materials mainly simulates transportation and storage pressure, and uses pressure differentials to detect leaks. Depending on your required detection accuracy and available equipment, there are three main methods, among which the vacuum attenuation method has the highest accuracy and the underwater bubble method is the most intuitive.

✔Mainstream Detection Methods

🔬Vacuum attenuation method (high precision/non-destructive)：The sample is placed inside the chamber and a vacuum is drawn. Leakage is detected by monitoring pressure changes. The sensitivity can reach ≤1×10⁻⁶ mbar·L/s, making it suitable for products with high sealing requirements.

💧Underwater bubble method (intuitive/low cost)：After filling the bottle with air (usually 20-100 kPa), immerse it in water and observe for continuous bubbles. This method can directly locate the leak point, but it is a destructive test, and tiny leaks may not be visible.

⏳Pressure decay method (with gas source container)：After inflating the container, turn off the gas supply and monitor the internal pressure drop. Acceptable standards include a pressure drop ≤1 kPa/min or a drop ≤5% within 30 minutes. Applicable to pump heads, spray cans, etc.

⚙Operating Procedures

Regardless of the method used, the process generally includes these steps:

1. Sample preparation: Ensure the sample is clean and dry, and seal all normal openings (e.g., plug the pump head with a rubber stopper).
2. Setting parameters: Refer to national standards (such as GB/T 15171) to set the pressure (such as 20-100 kPa) and the pressure holding time (30 seconds to 5 minutes).
3. Perform the test: Start the equipment and observe the pressure curve or visually inspect for bubbles.
4. Judgment result:

  Quantitative: The leakage rate must be lower than the standard, such as ≤0.1 mL/min.

  Qualitative: The absence of continuous bubbles indicates that the test is qualified.

5. Cleaning: After testing, wipe the sample dry and empty the water from the vacuum chamber.

⚠Key Precautions

Distinguishing between airtight and liquid-tight: Gas molecules are much smaller than liquid molecules, so passing the gas tightness test does not guarantee passing the liquid tightness test. The test medium must be selected based on the contents.

Simulates actual working conditions: The product's sealing performance may decrease after being dropped or stacked during transportation. It is recommended to conduct airtightness tests on samples that have undergone drop and vibration simulations.

Environment and Safety: When testing flammable materials, use inert gases such as nitrogen; ensure the gas source is clean and dry.

📌Summary and Recommendations

If you are conducting routine spot checks, the underwater bubble method (refer to GB/T 15171) offers the best cost-effectiveness; For factory inspection or R&D verification, vacuum decay method is recommended；For products like pump heads and sprayers, the pressure decay method is the most appropriate.