Are You Sure Your Bubble Leak Test Results are Accurate

During bubble-release leak testing, the presence of bubbles is often interpreted as a failure of the packaging seal. However, the hidden factor of trapped air is frequently overlooked, yet it can also cause bubbles to form. If this factor is not ruled out before testing, it is highly likely to result in false positive results, leading to the rejection of qualified products and affecting decision-making.

The Physics of the “Clinging Bubble”
Air often becomes trapped in the folds of flexible packaging. When a sample is placed in a test chamber filled with liquid, air adheres to the sample’s surface. As a vacuum is applied, pressure changes cause this “trapped air” to expand and detach from the sample’s surface, forming bubbles.

How to Differentiate a Real Leak from a False Positive
The “Steady Stream” Rule: In bubble release testing, a leak is typically identified when a continuous stream of bubbles is generated. If only a small number of bubbles appear sporadically, it is generally not considered a leak.

The “Static Exhalation” Trait: If bubbles appear at the very beginning of the vacuum extraction process but stop once the vacuum level stabilizes, a packaging leak can be ruled out.

Pre-Test Agitation: Before starting the vacuum test, gently agitate the sample to remove any air that may be trapped on its surface.

Mastering the methods to distinguish between true leaks and false positives allows for accurate assessment of packaging seal integrity and improves packaging performance.

If you’d like to learn more about leak detection methods, please refer to our Basic Guide to Leak Detection.