What Is a Mylar Bag?
A mylar bag is a foil-laminate pouch that blocks light and oxygen. What it's made of, why it stores food for decades, and its limits.
If you've read anything about long-term food storage, you've seen "mylar bag" everywhere. Here's what it actually is and why it works.
What it's made of
"Mylar" is a brand name for a type of metallised polyester film: a plastic layer bonded to a microscopically thin layer of aluminium. Food-storage mylar bags laminate that into a tough, flexible pouch. The aluminium is what makes the bag opaque and gives it its high barrier properties.
Why it works for food storage
Two things stale and spoil dry food: oxygen and light. Ordinary plastic lets both through slowly. Mylar's foil layer blocks light completely and is a far stronger barrier to oxygen and moisture. Drop an oxygen absorber inside before sealing, and the bag holds almost no oxygen at all, which is what takes rice and beans from a year to decades.
How it's used
A mylar bag isn't used on its own. The method is:
- Fill the bag with a dry staple.
- Add a correctly sized oxygen absorber.
- Heat-seal the top shut.
- Drop it into a food-grade bucket for pest and crush protection.
Bags come in sizes from quart to 5-gallon and thicknesses from 3.5 to 7 mil.
A bag is one piece of a system. Mylar plus an oxygen absorber plus a bucket is the setup; the bag alone doesn't preserve anything, the absorber does the oxygen removal and the bag holds that state.
What it's not for
Mylar is for dry goods. It won't preserve moist or oily foods, which need refrigeration or freezing, and it's not a substitute for vacuum sealing short-term freezer food.
The verdict
A mylar bag is a foil-laminate pouch that blocks light and oxygen, and paired with an absorber and a heat seal it's the standard way to store dry staples for decades. Choose the right size and mil, add an absorber, seal it, and bucket it.
A mylar bag is a food-grade foil-and-plastic laminate pouch that blocks light and strongly resists oxygen and moisture. Filled with a dry staple, an oxygen absorber, and heat-sealed, it stores rice, beans and wheat for 25 or more years. It's the standard container for long-term dry storage, but not for moist or oily foods.
Frequently asked questions
What is a mylar bag made of?
It is a food-grade pouch of metallised polyester, a thin laminate of plastic and aluminium. That structure blocks light and is a strong barrier against oxygen and moisture, far better than ordinary plastic bags.
Are mylar bags better than plastic bags?
For long-term dry storage, yes. Ordinary plastic lets oxygen and light through over time, while mylar blocks both, which is why it is the standard for storing staples for years. Plastic is fine for short-term use.
Do mylar bags need oxygen absorbers?
For long-term storage, yes. The bag blocks new oxygen from entering, and the absorber removes the oxygen sealed inside, so together they protect food for years. Without an absorber, the trapped air still lets food slowly degrade.
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