What Is a Mylar Bag? A Complete Guide for Long-Term Food Storage
A Mylar bag is a multi-layer storage pouch built to block the three things that spoil food: oxygen, light, and moisture.
It looks and feels like flexible foil, and when sealed with an oxygen absorber, it creates a near-airtight environment that keeps dry food fresh for years.
It is the reason a bag of white rice can sit on a shelf for two decades and still cook up the same.
New to food storage? Here is everything worth knowing before you buy your first bag.
What Mylar Actually Is
"Mylar" is a brand name. The material is BoPET (biaxially-oriented polyethylene terephthalate), a strong, thin polyester film first made in the 1950s. On its own, it is just clear plastic.
What makes a Mylar bag work for food is the layering. A proper food-storage bag has three bonded layers:
· Outer PET for strength
· Middle aluminum foil that does the actual blocking
· Inner food-grade PE that seals under heat and keeps food off the metal
That foil core is why a real food storage bag is always opaque and silver, never see-through.
You have handled Mylar before without knowing it. The same material shows up in foil balloons, emergency blankets, and insulation.
But those are not food storage bags, and that difference matters more than beginners realize.
How a Mylar Bag Works
Ordinary plastic breathes. Oxygen passes slowly through the walls, and over months it oxidizes fats, fades color, invites pests, and turns food stale.
A Mylar bag cuts that air transfer to almost nothing thanks to the foil layer, which blocks oxygen, light, moisture, and odor.
Here is the part beginners miss: the bag seals out new air, but it does not remove the air already trapped inside. That leftover oxygen is enough to spoil food over time.
This is why Mylar bags and oxygen absorbers go together. Drop a small absorber in before sealing, and it pulls the residual oxygen out.
The bag then holds that low-oxygen environment in place. One without the other only does half the job.
Storage, Not Preservation
This trips people up, so let us be clear: a Mylar bag does not preserve food, it stores it.
You are not canning or curing anything. You are taking food that is already shelf-stable, meaning dry, and extending how long it stays good by sealing it from the elements.
Start with dry rice and you get years. Start with something moist, and no bag will save it.
That one idea tells you most of what you can and cannot store.
What You Can Store in Mylar Bags
Mylar is built for dry, low-moisture food (ideally under about 10% moisture). The best candidates are the staples you would want in a long-term supply anyway:
· White rice, wheat, and whole grains
· Dried beans, lentils, and legumes
· Pasta and rolled oats
· Flour, sugar, and salt
· Freeze-dried meals and ingredients
For everyday single ingredients like coffee or a batch of beans, a smaller quart Mylar bag is the practical pick. For bulk staples you buy in volume, a 1-gallon bag holds more per seal.
What You Should NOT Store
The foods to avoid all share one trait: oil or moisture. Even with every trace of oxygen gone, fats turn rancid and moisture breeds spoilage on their own.
Keep these out of long-term storage:
· Oily or fatty foods (nuts, seeds, roasted coffee beans)
· Brown rice, which has natural oils that go rancid
· Jerky and other oil-rich snacks
· Home-dehydrated fruits and vegetables (they hold more moisture than they look)
· Brown sugar, molasses, and sticky items
· Fresh produce and dairy
Short version: if it is oily or holds any moisture, it does not belong in a long-term Mylar bag.
How Long Does Food Last in a Mylar Bag?
Sealed correctly, paired with an oxygen absorber, and kept cool, dark, and dry, many dry staples last up to 25 to 30 years depending on the food and conditions. Rice, beans, wheat, and sugar sit at the long end.
The conditions are not fine print. Heat and humidity shorten shelf life no matter how good the bag is, so for a bulk supply in 5-gallon bag, where you store them matters almost as much as the bags themselves.
How to Spot a Real Food-Grade Mylar Bag
Not every shiny bag online is built for food, and this is where new buyers get burned. Three quick checks:
· Opaque, not clear. If you can see through it, light gets through too. Real food storage Mylar is never transparent.
· Real thickness. Measured in "mil." Thicker bags (5 mil and up) resist punctures and hold a seal. Thin metalized films, like party balloons, have almost no oxygen barrier.
· Food-safe layers, with that inner PE lining keeping contents off the foil.
Buy thick, opaque, and food-grade the first time and you avoid finding out the hard way that the cheap option failed.
Sizes and Styles
Mylar bags run from quarter-pint pouches for spices to five-gallon bags for bulk grain. They also come in a few styles:
· Flat bags that stack neatly
· Stand-up bags with a flat bottom that hold their shape
· Resealable bags with a built-in zipper for food you open often
The most versatile option combines a zipper for daily access with heat-seal compatibility for the long term. If you are starting from scratch, a multi-size Mylar kit covers every size in one box so you can match the bag to the food.
Getting Started
It comes down to four things:
1. The right food (dry)
2. The right bag (opaque, thick, food-grade)
3. An oxygen absorber sized to the bag
4. A good seal, stored somewhere cool and dark
Get those right and you have a pantry that holds for years instead of months.
Frequently Asked Questions
Do you need oxygen absorbers with Mylar bags?
For long-term storage, yes. The bag blocks new air; the absorber removes the air already inside. Together they create the low-oxygen environment that keeps food fresh.
Are Mylar bags reusable?
The bags are, especially resealable ones. If you heat-seal a bag, seal it high so you can cut it open and reseal the zipper underneath. Oxygen absorbers are single-use once exposed to air.
Are Mylar bags food safe?
Genuine food-grade bags are, because the inner PE layer is food-safe and keeps contents off the aluminum.
Can you store liquids in Mylar bags?
No. Mylar is for dry goods only. Liquids and high-moisture foods will spoil regardless of the seal.
The Bottom Line
A Mylar bag is simple once you see how it works: an opaque, foil-layered pouch that locks out air, light, and moisture, paired with an oxygen absorber that clears the air left inside.
Get the food dry, the bag right, and the seal tight, and you turn months of shelf life into years.
That is the whole system.
If you are ready to start, Roylo Globe carries Mylar bags and oxygen absorbers in every size, from quart pouches to five-gallon bags, so you can match the bag to whatever you are storing and seal your first batch this week.