Testing laboratory for seal strength and tightness of packaging

What we test

Two questions come up particularly often for packaging: does the sealed seam hold, and is the package tight? We test both in our own laboratory on films, pouches, sacks, trays and cups.

• Seal strength: tensile test on strips, sealing curves, opening forces of peelable packages, seal seam quality of PE pouches, paper seals
• Tightness: leak tests, pores, micro-holes and defects using test gas, colour methods, penetrating oil, light box or original filling

Seal strength: accredited standards and sample quantity

The standards in this table are marked as accredited (Flex B) on the respective test method page. The DAkkS accreditation certificate (registration number D-PL-17789-01-00) is authoritative.

Test	Accredited standards	Required sample amount	Duration	Test order
Seal strength, tensile test on strips (-40 to +120 °C)	DIN 55529 (2012-09) ASTM F 88/F 88M (2023) DIN EN 868-5, Annex D (2019-03)	min. approx. 300 mm sealed seam or 10 packages	on request	Create test order
Sealing curves and sealing trials on the laboratory sealing press	DIN 55529, ASTM F 88/F 88M, DIN EN 868-5, Annex D, DIN 55409-1, DIN 55409-2, DIN EN ISO 527-3	approx. 1 m² or 15 DIN A4 sheets, minimum sample width 100 mm	on request	Create test order
Opening forces of peelable packages	DIN 55409-1 (2012-09, flexible packaging) DIN 55409-2 (2013-10, rigid packaging)	min. 10 package samples	on request	Create test order
Seal seam quality of PE pouches and sacks (-40 to +120 °C)	DIN 55529 (2012-09), DIN EN ISO 527-1, DIN EN ISO 527-3	at least 15 packaging units or product samples	on request	Send enquiry
Tensile test on paper and paper seals	DIN EN 868-4, DIN EN ISO 1924-2, DIN ISO 1924-3, DIN ISO 3781	approx. 0.1–0.2 m² or 2 DIN A4 sheets; min. approx. 150 mm sealed seam	on request	Create test order

The test method pages also list further standards that are not marked as accredited, for example DIN 55543-3 and GKV Blatt I–IV for the seal seam quality of PE pouches. We also offer the hot-tack test (strength of a seam that is still warm, DIN 55571-2).

Tightness: methods for leaks, pores and micro-holes

Which method is suitable depends on material and question. The methods are described in detail on the page Tightness, leakage test, pores, micro-holes, defects. The sample quantity depends on the task, the duration is available on request. The test method page does not mark these methods as accredited.

Method	Standard / leaflet	What it can detect
Test gas method (forming gas, hydrogen probe)	IVLV Merkblatt No. 102	Very sensitive, locates the smallest leaks; suitable for empty packages, dry contents or cleaned packages
Colour method (methylene blue in ethanol)	DIN 55508-2	Leaks from approx. 10–20 µm
Dye penetration (aqueous dye solution)	ASTM F 1929	Leaks from approx. 50 µm
Light box inspection	DIN EN 546-4	Pores from approx. 20 µm, especially for web materials such as aluminium foil
Penetrating oil method	In-house method PV036	Finest pores and cannulas (pinholes)
Test with original filling	In-house method PV036	Verification of results with real contents
Pore tightness of coatings on aluminium foil	FhG Merkblatt 29 Blatt 1	Pores in the coating by chemical copper deposition
Resistance against leakage (plastic sacks)	DIN EN 13592	Filling with water or a water/sawdust mixture

To prepare an offer for a tightness test we need the following information:

• What kind of packaging should be tested (size, filling volume)?
• How many packages should be tested?
• Are the packages empty or do they have to be emptied before testing?
• Which contents are involved (CAS no./safety data sheet)?

For tightness testing you can contact us directly or create the test order right away: order tightness test.

How to place a test order

• Choose the test method in the table and enter the test parameters via “Create test order”.
• Send in samples in the stated minimum quantity.
• If you have questions about the choice of method, the laboratory will advise you: get in touch.

Go to test order · All mechanical test methods · All permeation and tightness tests · All standards

Frequently asked questions

Which standards apply to seal strength testing?

For tensile tests on strips of sealed seams we test to DIN 55529, ASTM F 88/F 88M and, for medical packaging, DIN EN 868-5 Annex D. We determine the opening forces of peelable packages to DIN 55409-1 and DIN 55409-2. These standards are listed in our accreditation to DIN EN ISO/IEC 17025.

How many samples are needed for the tensile test on strips?

For the tensile test on strips we need at least approx. 300 mm of sealed seam or 10 packages. For sealing curves on the laboratory sealing press we need approx. 1 m² of film or 15 DIN A4 sheets with a minimum sample width of 100 mm.

How many packages are needed to test opening forces?

For determining the opening forces of peelable packages to DIN 55409 we need at least 10 package samples.

How long does a test take?

We state the duration of a test on request. Please contact us via the contact form or the test order.

Which methods can locate leaks and micro-holes in packaging?

Depending on material and question we use the test gas method (hydrogen probe), the colour method with methylene blue to DIN 55508-2 (leaks from approx. 10–20 µm), dye penetration to ASTM F 1929 (leaks from approx. 50 µm), the penetrating oil method, light box inspection (pores from approx. 20 µm) and tests with the original filling.