Gum seal envelopes — also called moisture seal or remoistening seal envelopes — use a traditional water-activated adhesive strip on the flap. Moisten the glue with a sponge, damp cloth, or envelope sealing machine, press the flap down, and it’s sealed. These are the standard choice for check mailing, invoice processing, remittance envelopes, and any high-volume mailing application. The interactive guide below illustrates exactly how a gum seal works.

How Gum (Moisture) Seal Envelopes Work

Activate with moisture: Apply water via tongue, damp sponge, or sealing machine to the adhesive strip.
Tamper-evident: The sealed flap tears visibly when opened — a clear sign of tampering.
Machine-compatible: Works with automated folding, inserting, and sealing equipment.
Best for: Checks, invoices, bills, government notices, and remittance envelopes.

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