How to test the sealing performance of a cosmetic bottle set

The sealing performance of a cosmetic bottle suit plays a critical role in ensuring product stability, shelf-life, and user experience. Cosmetic formulations often contain volatile ingredients, active substances, and components sensitive to oxidation. The packaging must maintain airtight integrity under various handling, transportation, and storage conditions. A comprehensive sealing test evaluates how well the entire bottle suit—including the bottle body, cap, pump, thread fit, gasket, and liner—prevents leakage and external contamination.

Importance of Sealing Performance Evaluation

Cosmetic products rely heavily on packaging to maintain formula quality. Poor sealing may lead to oxidation, evaporation, viscosity changes, microbial growth, and customer complaints. Even a high-quality formula may lose stability if the packaging cannot provide reliable sealing. Bottle suits that include multiple components such as pumps, droppers, and screw caps require stricter sealing assessments, as each interface impacts overall airtightness.

Vacuum Leak Test

The vacuum leak test determines whether the cosmetic bottle suit maintains its integrity under negative pressure. The assembled bottle is placed inside a vacuum chamber, and pressure is reduced to a specified level for a set duration. Observations focus on deformation, bubble generation, or liquid leakage. Vacuum testing exposes imperfections such as micro-gaps in threads, loose pump assemblies, and weak bonding points. This method is widely used for PET bottles, glass bottles, acrylic bottles, and airless containers due to its high accuracy in identifying hidden leaks.

Water Bath Pressure Test

The water bath pressure test evaluates sealing reliability by pressurizing the bottle interior and observing bubble formation underwater. Pressurized air is injected into the filled bottle, and the entire container is submerged in a water tank. Continuous bubbles indicate leakage paths at the bottle neck, pump interface, or thread engagement areas. This test is suitable for lotion bottles, spray bottles, serum bottles, and pump-style containers. Water bath testing provides clear visual results and uncovers small structural defects that may not be detected through visual inspection alone.

Static Leakage Test

The static leakage test simulates daily usage scenarios. The cosmetic bottle suit is filled with a designated liquid and stored in a controlled-temperature environment. The bottle is placed in different orientations such as inverted, horizontal, and upright positions to assess leakage over time. This method detects issues related to thread precision, gasket hardness, pump return mechanism, and dimensional tolerance deviations. Static leakage testing offers valuable real-world evidence of how the packaging performs during consumer use.

Drop Impact Test and Sealing Confirmation

Drop impact testing verifies structural durability and sealing stability under mechanical shock. The cosmetic bottle suit is dropped from a specified height at multiple angles. After impact, the packaging is examined for cracks, deformation, and leakage at the neck, shoulder, pump joint, or airless mechanism. Packaging combinations such as glass bottles with plastic caps, acrylic dual-layer structures, and soft plastic bottles require especially careful evaluation. Micro-cracks may not be visible externally but can be detected through subsequent sealing tests.

Torque Test and Locking Stability

Threaded components rely on proper locking strength to maintain sealing. Torque testing measures the opening and closing torque of caps and pumps to verify whether the tightening force meets standards. Insufficient torque results in poor sealing, whereas excessive torque can damage threads or create stress points. A torque tester provides precise values to ensure consistent locking performance during mass production. Bottle suits containing multiple parts benefit from torque monitoring to ensure a reliable and repeatable sealing condition.

Air Leak Testing with Automated Leak Testers

Automated leak testers provide fast, quantitative sealing evaluations. The bottle suit is placed inside a sealed test chamber, and pressure sensors monitor changes in internal pressure. Any drop in pressure signifies leakage. Air leak testers offer high sensitivity and can be integrated with production lines for batch sampling or 100% inspection. This method is valuable for large-scale cosmetic packaging manufacturing where speed and repeatability are critical.

Compatibility Testing and Its Influence on Sealing

Cosmetic formulas interact with packaging materials in different ways. Some ingredients may soften, swell, or degrade gaskets, pump springs, or threaded components over time. Alcohol-based, acidic, or highly volatile formulas may compromise sealing materials. Compatibility testing evaluates how the cosmetic bottle suit performs when exposed to actual product ingredients for extended periods. This assessment verifies whether sealing components maintain elasticity, hardness, and structural stability during long-term use.

Evaluation Criteria for Sealing Performance

Quantitative sealing assessments involve multiple data points, including pressure variation, bubble frequency, mass change, visual inspection, and structural integrity. Each type of cosmetic bottle suit—airless bottles, glass bottles, pump bottles, sprayers, and screw-cap bottles—has defined tolerance ranges. A passing result indicates the packaging can reliably protect the product throughout its lifecycle. Strong sealing performance enhances transportation safety, extends product shelf life, and reinforces brand quality perception.