Testing Do Not Bend Envelopes for Strength and Durability
Test your envelopes before bulk ordering with these practical strength and durability checks.
Bend resistance test
Quick answer
Test bend resistance by holding packed envelopes by one end (should not sag), pressing the centre (should resist), and flexing gently (should spring back). Test seal strength by pulling the sealed flap firmly. Ship 5-10 test envelopes through your actual postal service and inspect on arrival. These simple tests catch quality problems before they reach customers.
Seal strength test
A quality seal should resist peeling and tear the paper before releasing.
Contents should not escape from a properly sealed envelope.
Quality adhesive maintains bond strength in warm conditions.
Quality: GSM guide or bend resistance.
Transit simulation
Ship testing0 / 3 checked
Quality-tested envelopes
Board-backed envelopes tested for strength from ProcuraPack.
Browse do not bend envelopesFrequently asked questions
Hold packed envelope by one end - should not sag. Press centre - should resist. Flex - should spring back.
Pull the sealed flap firmly. It should tear the paper rather than peeling open.
Yes, send 5-10 to yourself through Royal Mail to check real-world performance.
Sagging when held by one end, seal that peels open easily, or board that bows permanently when flexed.
At least 5-10 samples from any new supplier or batch.
Part of our guide
Product Guide: Do Not Bend Envelopes
Expert guides on rigid mailers and board-backed envelopes for protecting documents, prints, and certificates.
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