How to Define Vacuum Level and Test Time for Bubble Leak Testing
ASTM D3078 describes a bubble-emission method for detecting gross leaks in flexible packaging, but one vacuum level cannot be applied safely and effectively to every package.
This guide separates the standard's instructions from DVACI's practical method for developing package-specific parameters.
What vacuum and time should be used?
Use the highest practical vacuum that provides a useful pressure differential without causing unacceptable package deformation, seal failure or test-fluid behavior that obscures the observation. The target must be developed for the specific package.
After reaching the selected level, the package is observed for the duration specified by the approved procedure. Consult the current standard for its exact requirements.
ASTM D3078 defines the method—not a universal recipe.
The flexible package is submerged in a test fluid, vacuum is applied and the operator observes whether bubbles escape from a specific location.
Position the package
Submerge the package according to the apparatus and method requirements.
Increase vacuum gradually
Avoid rapid loading that may distort the package or create misleading behavior.
Evaluate bubble emission
Distinguish a package leak from trapped air or bubbles generated by the test fluid.
Why parameters must be developed
Package size, materials, headspace, seal design, mechanical strength and the test fluid all affect how the sample responds. Therefore, parameter development must balance sensitivity with package and fluid limitations.
Four limits determine the usable vacuum range.
ASTM discusses package and fluid limitations. DVACI also evaluates atmospheric-pressure variation when the package will travel through changing altitude conditions.
Package fragility
The seal or structure may deform, open or fail before the desired vacuum is reached.
Package expansion
Flexible packages can expand enough to change internal pressure and reduce useful sensitivity.
Test-fluid behavior
Dissolved gas release can create bubbles unrelated to a package defect.
Altitude exposure
Expected transport conditions may require a complementary pressure-simulation evaluation.
Begin by understanding the package failure level.
Identify the point at which the package starts to deform unacceptably or fail. DVACI may use approximately 70% of that measured failure vacuum as an initial operational target for development testing.
This is a practical DVACI heuristic—not a requirement or formula stated by ASTM D3078. It must be verified against the actual package and test objective.
More vacuum does not always produce a better test.
Excessive package expansion changes the internal conditions of flexible packaging. Very low absolute pressure can also cause the test fluid to release dissolved gas, producing bubbles that do not originate from a leak.
Package expansion
Elastic materials may expand substantially, changing headspace volume and package behavior.
Fluid degassing
Dissolved gases may leave the liquid before its normal boiling point is reached.
False bubbles
Bubbles generated throughout the fluid can obscure or be confused with package emissions.
Interpretation rule: A localized, repeatable stream from the package is different from widespread fluid degassing or air released from chamber surfaces. Operators must be trained to distinguish these behaviors.
Pre-degas the test fluid before extreme-vacuum work.
When high vacuum is necessary, DVACI recommends conditioning the fluid before introducing samples. This reduces dissolved gas and makes package-related bubbles easier to interpret.
Consult the applicable standard and laboratory procedure when defining fluid, vacuum and conditioning time.
Separate leak detection from altitude simulation.
A package may need both a leak-detection method and a complementary evaluation of its response to the pressure differential expected during air transport.
Define the exposure
Establish the altitude or pressure condition relevant to distribution.
Run the leak test
Use the package-specific D3078 conditions developed for useful leak detection.
Evaluate altitude separately
Use an appropriate ASTM D6653 procedure for the transport-simulation objective.
Method distinction: ASTM D3078 addresses bubble-emission leak detection. ASTM D6653 addresses the effects of high altitude on packaging systems by vacuum method. They answer related but different questions.
Confirm the setup with a known control sample.
A control sample contains a known defect and helps determine whether the selected setup can reveal the intended leak under the chosen conditions.
It does not replace method validation, but it provides a practical check that the equipment, fluid, parameters and observation technique can produce the expected indication.
ASTM D3078 Vacuum and Time FAQ
Does ASTM D3078 prescribe one vacuum level for every package?
No. The usable level depends on the package structure, materials, headspace, strength and behavior under reduced pressure.
Is the 70% rule an ASTM D3078 requirement?
No. It is a practical DVACI starting point for development after measuring the package failure level. It must be verified for the specific application.
Why can high vacuum create false bubbles?
At sufficiently low absolute pressure, dissolved gas may leave the test fluid and create bubbles unrelated to a package leak.
Is an altitude-simulation test the same as ASTM D3078?
No. ASTM D3078 is a bubble-emission leak method, while ASTM D6653 evaluates packaging systems under simulated high-altitude conditions.
Why use a control sample?
A known defect helps confirm that the chosen equipment, parameters and observation technique can reveal the targeted leak indication.
Define vacuum and time with your actual package.
Share your samples, package details and test objective with DVACI.
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