Knowledge Base
Burst Testing – Glossary & Key Facts
A reference guide to the key terms used in burst strength testing and seal quality assessment for flexible packaging manufacturing.
Burst Strength The maximum internal pressure – expressed in kPa, mbar, or PSI – that a sealed flexible package can withstand before the seal or material fails. The primary output of a burst strength test and a core indicator of sealing process performance.
Burst Testing A destructive test method in which a sealed package is inflated with air or gas at a controlled rate until the seal or package structure fails. Measures seal strength and material resistance. Used for quality control sampling and R&D seal validation. The BT Integra is a purpose-built burst testing instrument for flexible packaging.
Heat Seal The bond formed between two layers of film or packaging material using heat and pressure. The strength of the heat seal is a primary determinant of burst strength and is influenced by seal jaw temperature, dwell time, and pressure settings.
Seal Jaw The heated component of a packaging machine that applies heat and pressure to create a heat seal. Seal jaw condition and settings are critical variables in seal strength performance and should be validated regularly using burst testing data.
Inflation Rate The speed at which internal pressure is applied to a package during a burst test. Inflation rate directly affects the measured burst strength result and must be kept consistent across test sessions for valid comparison. Defined in applicable test standards such as ASTM F2054.
Failure Mode The location and nature of a package’s failure during a burst test – whether at the seal, a corner, or through the film material. Failure mode analysis provides diagnostic information about the source of structural weakness in a package.
Restrained Burst Test A burst test method in which the package is constrained within a fixture during inflation, preventing it from expanding freely. This method – covered by ASTM F2054 – isolates the seal as the primary failure point, providing a more direct measure of seal strength.
Unrestrained Burst Test A burst test method in which the package is allowed to expand freely during inflation. This method – covered by ASTM F1140 – tests the overall pressure resistance of the package, including both the seal and the material.
ASTM F2054 Standard test method for burst testing of flexible package seals using internal air pressurisation within a restrained package. The primary applicable standard for burst strength testing in flexible packaging quality assurance.
ASTM F1140 Standard test methods for internal pressurisation failure resistance of unrestrained packages. Covers burst and creep testing of flexible packaging formats.
Creep Testing A related test method in which a package is held at a defined constant pressure over a set time period to assess whether the seal can sustain load without failure. Used alongside burst testing to evaluate seal durability. Covered by ASTM F1140.
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FAQs
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Burst strength testing is a quality assurance method in which a sealed flexible package is inflated with air or gas at a controlled rate until the seal or material fails. The maximum pressure reached at the point of failure – the burst strength – is a direct measure of how structurally robust the package and its seals are.
For quality managers and R&D specialists in flexible packaging production, this matters for several reasons. A package that passes visual inspection may still have seals that are insufficiently strong to survive the rigours of distribution, stacking, or consumer handling. Burst testing reveals these weaknesses before they become market failures – giving teams the data they need to validate sealing process settings, identify process drift, and protect the integrity of the product inside.
Burst testing is also an important tool for new packaging development. When evaluating new film structures, seal geometries, or heat seal parameters, burst strength data provides a quantitative basis for comparison that subjective assessment cannot match. The BT Integra from Industrial Physics supports both production QC and R&D applications, delivering the repeatability and precision that meaningful seal validation requires.
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The BT Integra inflates a sealed package sample with air at a controlled, defined rate – continuously monitoring internal pressure as it rises. When the seal or package material reaches its structural limit and fails, the instrument detects the resulting pressure drop and records the peak pressure value reached at the point of failure.
This peak pressure value is the burst strength result for that sample. The BT Integra logs the result along with relevant test parameters, building a data record across samples and production runs that quality and R&D teams can use for trend analysis and process validation.
The test is conducted on a sample basis – it is a destructive method, meaning the package is pressurized to failure and cannot be returned to the line. This is why burst testing is used alongside, not instead of, inline integrity testing methods. To see the BT Integra in operation, watch the demonstration video.
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The distinction between restrained and unrestrained burst testing relates to whether the package is constrained during the test, and it has a direct effect on what the result tells you.
In a restrained burst test – governed by ASTM F2054 – the package is held within a fixture that prevents it from expanding freely during inflation. This means the pressure is concentrated at the seals rather than distributed across the film surface. The result is a more direct measure of seal strength, making restrained testing the preferred method when the primary objective is to evaluate sealing process performance.
In an unrestrained burst test – covered by ASTM F1140 – the package inflates freely. Pressure is distributed across the entire package, and failure may occur at the seal, a corner, or through the film material. This approach provides a measure of overall package pressure resistance rather than seal strength in isolation.
For most production quality assurance applications where the goal is to validate that the sealing process is producing consistently strong seals, restrained burst testing is the more relevant method. Your choice of test method should always be documented and kept consistent across test sessions – the BT Integra supports both approaches.
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