Why You Should Put an Envelope in the Freezer

Updated: Sep. 05, 2023

Accidentally seal an envelope prematurely? Fret not.

It’s happened to all of us: You seal an envelope, then realize you forgot to enclose something. Now you can’t reopen the envelope without wrecking it.

Or can you?

Placing an envelope in the freezer to loosen its seal might sound bizarre, but it’s a trick employed for years to avoid damaging the envelope or its contents. This is due to thermal expansion and contraction, which can gently break the envelope’s adhesive seal bond.

While it’s not a foolproof method and might not work for every envelope, it can be a handy solution in certain situations.

The Science Behind the Hack

The adhesive seal on envelopes is typically composed of materials sensitive to temperature changes. After you seal an envelope, the liquid adhesive dries and hardens, creating a tight bond. However, when subjected to temperature fluctuations, the adhesive expands or contracts, causing stress on the bond.

By placing a sealed envelope in the freezer, you’re essentially creating a controlled environment that encourages the adhesive to contract. As the adhesive shrinks, it often creates micro-fractures along the bond, making it easier to gently pry the envelope open without tearing the paper.

Does It Work?

In some instances, yes. But it’s not guaranteed to work every time.

The effectiveness of this hack depends on the type of adhesive, the quality of the envelope, the amount of time in the freezer and other variables. Strong adhesive and specialized sealing mechanisms might not respond to the technique.

How to Do It

  • Prep: Place the envelope in a resealable plastic bag to protect the contents from any moisture that could occur during freezing.
  • Temperature exposure: Leave the envelope in for at least an hour but not longer than two. Extreme cold might damage the envelope or its contents.
  • Removal and opening: Gently try to open the envelope with a letter opener or your fingers. If the adhesive has loosened, the flaps should separate without tearing the paper. If the envelope remains stubbornly sealed, resist the temptation to force it open. Instead, let it gradually return to room temperature and try again later. Repeat the freezing process may further encourage the adhesive to contract.