Mylar bags are flexible pouches made from laminated polyester film with a metallised or foil barrier layer, sealed with heat. They block light, oxygen and moisture, they don't let smell through, and they're cheap. That combination is why they're the default package for cannabis flower, coffee, jerky and long-term food storage. "Mylar" is a DuPont brand name for polyester film that became the generic word, the way "Kleenex" did for tissues. Here's what they are, what they're used for, and how to pick the right one.
What a mylar bag is made of
A typical bag is three layers glued together: polyester (PET) on the outside for strength and print, a metallised layer or aluminium foil in the middle for the barrier, and polyethylene (PE) on the inside, which is the part that melts and seals. Total thickness is measured in mil, thousandths of an inch. Flower bags are 3.5 to 5 mil; long-term food storage bags are 5 to 7 mil. The full layer-by-layer breakdown is in what are mylar bags made of.
A bag with no barrier layer, just clear or tinted PET/PE, is often sold as "mylar" too. It seals the same way but lets light and oxygen through. When the barrier matters, ask for the layer structure.
What mylar bags are used for
Cannabis. The main retail format for flower in most licensed markets: 1g, 3.5g, 7g, 14g and 28g sizes, opaque, child-resistant zipper, printed with the brand. Also used for edibles and pre-roll multipacks. See custom mylar bags.
Coffee. Roasters use the same bags with a one-way valve added to let CO2 out.
Food storage. Rice, beans, grains and freeze-dried food in 1-gallon and 5-gallon bags with oxygen absorbers, sealed for 10 to 25 years.
Snacks and jerky. Anything that goes stale in air.
Electronics and documents. Anti-static and moisture protection.
The cannabis and food-storage uses have different priorities. Food storage wants maximum thickness and a foil layer for decades of shelf life. Cannabis wants a bag that looks good, opens and closes daily, and keeps flower fresh for a few months. The bags overlap but aren't the same product.
Features that vary
Zipper. Resealable zippers on most cannabis and snack bags. Long-term food storage bags often have none; they're heat-sealed once and cut open.
Child-resistant closure. Required for cannabis in every licensed state. A CR zipper needs two motions to open, usually pinching a tab while sliding, and the bag has a tear notch above it. Details in child-resistant packaging.
Shape. Stand-up pouches with a gusset at the bottom stand on a shelf. Flat pouches are cheaper and pack tighter. Die-cut shapes, jars and bottles and custom outlines, are a printed marketing format. See die-cut mylar bags.
Window. A clear strip or shape so the product is visible. Reduces the barrier at that spot and most cannabis regulations forbid it on flower packaging, though it's common on edibles and food.
Finish. Gloss, matte, soft-touch, holographic, kraft paper face. Cosmetic, doesn't change the barrier.
Print. Stock bags are plain colours with a label applied. Custom bags are printed directly, usually with an 8 to 10 colour rotogravure or digital process, at minimums that start around 500 to 1,000 pieces for digital and 5,000 to 10,000 for gravure.
Are they smell-proof, safe and recyclable?
Smell-proof yes, when sealed and when the zipper is a good one. Safe yes, the inner layer is food-grade polyethylene. Recyclable mostly no, because the layers can't be separated at normal facilities. All three in detail in are mylar bags smell-proof, safe, reusable and recyclable.
How to seal one
A zipper bag closes with the zipper for daily use. For a permanent seal, an impulse heat sealer or a household iron on the PE layer fuses the top shut. Method and settings in how to seal mylar bags.
Which mylar bag to buy
Flower, retail: 3.5 to 4 mil, opaque, CR zipper, stand-up, matte or gloss print. The comparison is in best mylar bags for weed.
Flower, storage: 5 mil, foil barrier, heat-sealed, with a humidity pack.
Food, long-term: 5 to 7 mil, foil, no zipper, with an oxygen absorber, heat-sealed.
Edibles: 3.5 to 4 mil, CR zipper, often with a window, food-grade inner layer. See cannabis edibles packaging.
CBD and hemp products: same as flower bags, often with a clear window since the CR and opacity rules are lighter. See CBD mylar bags.
Quick answers
What are mylar bags? Pouches made of laminated polyester film with a barrier layer, heat-sealed, that block light, oxygen, moisture and smell.
What are mylar bags used for? Cannabis flower and edibles, coffee, snacks, long-term food storage, and anything that degrades in air or light.
Is mylar a brand name? Yes. DuPont's trademark for polyester film. It's used generically for any barrier pouch.
How long do mylar bags keep things fresh? Months for flower with a humidity pack, 10 to 25 years for dry food with an oxygen absorber in a thick foil bag.
Are mylar bags airtight? When heat-sealed, yes. A zipper seal is close but not perfectly airtight over long periods.
