What Is Mylar, and Why Use It for Food Storage?

Mylar bags are the standard for storing freeze-dried food long term, and there's a real reason why: the material blocks the three things that break food down fastest — oxygen, moisture, and light.

What Mylar Actually Is

Mylar's official name is BoPET (biaxially-oriented polyethylene terephthalate), though almost nobody calls it that. It's the same material used in balloons, thermal insulation, kites, various packaging, and the reflective blankets handed out at the end of a marathon. Its properties — extremely light, flexible, thin, and still strong and durable — make it just as useful for food storage as for those other applications.

Why It Works So Well for Food

Mylar seals out oxygen, moisture, and light — the three biggest factors in food breaking down over time — while also keeping unwanted odors from passing through the bag in either direction. That combination is what allows properly packaged freeze-dried food to last as long as it does.

How to Store Food in Mylar Correctly

Add an oxygen absorber to the bag before sealing it — this pulls out any oxygen that gets trapped inside before the seal closes. Seal the bag with heat, using a bag sealer or a household iron, sealing only about the top inch of the bag. Store sealed bags inside a bucket or plastic bin rather than leaving them out in the open, since rodents and insects can chew through Mylar on their own. Keep storage temperature below 85°F — the cooler and more stable, the better. Done this way, freeze-dried food can last up to 25 years.

Reusing Mylar Bags

If a bag is opened carefully, it can be resealed and reused for another batch rather than needing a fresh bag every time.

More on Packaging and Storage

How to package freeze-dried food so it keeps for 25 years goes deeper into the full packaging process, and storing freeze-dried food covers where and how to keep it once it's sealed. Organizing a prepper's pantry is a good next read if long-term storage is part of a bigger food-storage plan.

Frequently Asked Questions

What is Mylar made of?
Mylar is the common name for BoPET (biaxially-oriented polyethylene terephthalate), a strong, lightweight, flexible plastic film also used in balloons, insulation, and reflective emergency blankets.

Why is Mylar good for storing freeze-dried food?
It blocks oxygen, moisture, and light — the three main factors that cause stored food to break down — and also prevents odors from passing through the bag.

How do you properly seal a Mylar bag for food storage?
Add an oxygen absorber before sealing, then heat-seal about the top inch of the bag using a bag sealer or household iron.

Can Mylar bags be reused?
Yes — if opened carefully, a Mylar bag can be resealed and used again for another batch of food.

What temperature should Mylar-packaged food be stored at?
Below 85°F, and as cool and stable as possible — properly stored freeze-dried food in Mylar can last up to 25 years.