Burst Strength Testing Explained: How It Works and When to Use It

Overview

Burst strength testing is one of the most widely used methods for evaluating the performance of sealed flexible packaging. It applies controlled internal pressure to a package until failure, measuring the point at which the seal or material gives way. 

For quality managers, R&D specialists, and operations experts working across flexible packaging production, burst testing answers a question that visual inspection and basic seal audits cannot: is this sealing process producing packages strong enough to survive the demands of distribution, retail, and end use? The data it generates is used to validate heat seal settings, compare film structures, benchmark performance across production runs, and support new packaging development. 

What is burst strength testing?

Burst strength testing works by inflating a sealed package with air or gas at a controlled, increasing rate. The instrument monitors internal pressure continuously as it rises. When the seal or package material reaches its structural limit and fails – whether by seal peeling, material rupture, or closure failure – the system records the maximum pressure reached at the point of failure. 

This peak pressure value is the burst strength of the package. It is expressed in units of pressure – typically kPa, mbar, or PSI – and compared against a defined acceptance threshold for the package type and application in question. 

Where does burst testing sit in the production process?

Burst testing is most commonly used in two contexts. In quality control, it is used to test samples from production runs – confirming that the sealing process is operating within specification and that packages are meeting the required strength thresholds. In R&D, it is used during new packaging development to evaluate different material combinations, seal geometries, and heat seal parameter settings. 

It is typically a destructive test – the package is pressurised to failure, which means it cannot be returned to the line. This is why it is used on a sample basis rather than for 100% inspection, and why it is complementary to rather than a replacement for inline integrity testing methods. 

Equipment and setup

Effective burst testing requires an instrument that delivers controlled, consistent pressure inflation and accurately records the failure point. Key components include an inflation system capable of applying pressure at a defined rate, a pressure transducer for continuous monitoring, a test fixture or chamber that holds the package securely during inflation, and data capture software that records the peak pressure at failure. 

See the BT Integra in use – watch the demonstration video → 

The BT Integra from Industrial Physics combines all of these elements into a dedicated burst testing instrument for flexible packaging. It delivers the repeatability and precision that quality and R&D teams require for meaningful process validation and statistical comparison between test batches. 

The test procedure 

1. Sample preparation – a sealed package sample is selected from the production run or R&D batch
2. Package loading – the package is placed in the test fixture and connected to the inflation system 
3. Inflation – the instrument inflates the package with air or gas at a controlled, defined rate 
4. Pressure monitoring – the pressure transducer monitors internal pressure continuously as it rises 
5. Failure point detection – when the seal or material fails, the system detects the pressure drop and records the peak value 
6. Data output – the burst strength result is logged against the sample reference for quality records and trend analysis 

What does burst testing tell you about seal quality? 

The burst strength value gives quality and R&D teams a direct indicator of seal robustness – but its real value is in what changes in burst strength reveal over time. 

A sudden drop in burst strength across a sample batch may indicate that seal jaw temperature has drifted, dwell time is insufficient, or that a new film reel has different sealing characteristics from the previous one. Conversely, consistently high and stable burst strength results indicate a sealing process that is well controlled and producing to specification. 

This is why burst testing data should be reviewed not just as a pass/fail check but as a process monitoring tool. The BT Integra captures result data on every test, enabling trend analysis across production runs, shifts, and material batches – turning routine QC testing into actionable process intelligence. 

Burst testing and seal integrity: understanding the relationship

Burst testing is often described as a seal integrity test – and while that framing is broadly correct, it is worth understanding precisely what it does and does not tell you. 

A burst test confirms the strength of a seal under controlled pressure conditions. A package that achieves a high burst strength has a seal that is structurally robust. However, burst testing does not detect existing microleaks, pinholes, or barrier failures in a package – these require dedicated leak detection methods such as pressure decay or vacuum decay testing. 

In a well-designed quality assurance programme for flexible packaging, burst testing and leak detection serve complementary roles. Burst testing validates that the sealing process is producing strong, consistent seals. Leak detection confirms that no individual package has a defect that has already formed. Together, they provide a more complete picture of package integrity than either method alone. 

Applicable standards 

ASTM F2054 – Standard test method for burst testing of flexible package seals using internal air pressurisation within a restrained package. The most directly applicable standard for burst testing of flexible packaging seals. 

ASTM F1140 – Standard test methods for internal pressurisation failure resistance of unrestrained packages. Covers both burst and creep testing of flexible packaging. 

Common errors and best practices

Inconsistent inflation rate is one of the most common sources of variability in burst test results. The rate at which pressure is applied affects the measured burst strength – faster inflation typically produces higher burst values. Always define and document the inflation rate used, and keep it consistent across test sessions for meaningful comparison. 

Inadequate sample size is another frequent limitation. A single burst test result tells you relatively little; the value of burst testing lies in statistical analysis across multiple samples. Follow the sample size requirements defined in the applicable standard and your own internal quality protocols. 

Failure mode observation is an often-overlooked aspect of burst testing. Where exactly the package fails – whether at the seal itself, at a corner, or through the film – provides important diagnostic information about the source of weakness. The BT Integra supports this by delivering consistent, controlled test conditions that make failure mode analysis reliable and repeatable. 

Why burst testing matters for brand protection 

For flexible packaging producers supplying global food, beverage, and consumer goods brands, package performance under real-world conditions is a direct expression of product quality. Packages that fail in transit, on shelf, or in the consumer’s hands damage brand reputation – and the root cause is almost always a sealing process issue that consistent burst testing would have caught. 

Industrial Physics supports quality, R&D, and operations experts with best-in-class burst testing technology, backed by unmatched application knowledge and a global service network. Learn more about the BT Integra and how it supports seal quality assurance across flexible packaging production.