Last updated: August 23, 2026
Sealing mylar is the step where a pantry project either becomes storage or becomes an expensive way to keep rice in foil. The bag itself does nothing until the top is fused shut, and a seal that looks fine but has a wrinkle running through it will let oxygen back in slowly enough that you will not notice until you open the bag a year later.
There are three real ways to close a mylar bag and one that people improvise with. This guide covers which tool suits which volume of work, where the cheap machines struggle, and how to check a seal before you trust a bucket of grain to it.
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Quick Answer
What do you use to seal mylar bags?
- An impulse sealer is the standard answer. It clamps the bag and heats a wire strip for a set time, giving a consistent seal width.
- A heat sealing iron or a clothes iron over a board works for occasional use and for bags wider than your sealer.
- A vacuum sealer cannot do this job, because it needs textured bag walls to pull air through.
- Match the sealer bar length to your widest bag, or plan on sealing in overlapping passes.
Bottom line: buy an impulse sealer long enough for your bags, and keep an iron as the backup for the oversized ones.
Why Mylar Needs a Heat Seal
Mylar food bags are a laminate with a heat sealable inner layer, and closing one means melting that layer against itself until the two faces become one. A zipper, a clip or a fold does not do that. Zipper topped bags are convenient for reopening, but the zipper is not the barrier and a bag going into long term storage still gets heat sealed above it.
That is also why the seal has to be clean. Any grain, dust or flour caught in the seal line stops the two faces fusing across the full width, and a wrinkle creates a channel. Wipe the inside of the bag mouth before sealing, which takes three seconds and prevents the most common failure.
The Vacuum Sealer Confusion
Plenty of people buy a household vacuum sealer expecting it to handle mylar. It cannot draw air out of a smooth walled mylar bag, because those machines rely on the embossed channels in their own bags to move air. Our guide to mylar bags and vacuum sealers covers the exceptions and the workarounds.
Impulse Sealers
An impulse sealer is a clamp with a heating element in the jaw. You set a dial, press the bar down, and the element heats for a moment and cools while still clamped, which is what gives a flat, even seal. It is the tool the job is designed around, and for anyone sealing more than a handful of bags it pays for itself in consistency alone.
Two specifications decide whether one suits you. Bar length has to cover the width of your bags, and seal width, quoted in millimeters, decides how wide the fused band is. A wider seal band is more forgiving of a small imperfection, which matters most on heavy 5 gallon bags.
The Honest Limitation
Owners of budget impulse sealers consistently report the same issue on long sessions: the unit gets hot and starts producing weaker seals, or the element burns out. These machines are designed with a duty cycle in mind, and a bucket lining marathon exceeds it. If you seal thirty bags in an afternoon, either buy a heavier machine or build in pauses.
Choosing the Bar Length
Measure the flat width of your largest bag and buy a sealer at least that long. A 5 gallon mylar bag is wide, and sealing it on a short bar means two or three overlapping passes, each one a chance to leave a gap where the passes meet. For gallon bags and smaller, a shorter and cheaper machine is genuinely enough.
If most of your work is gallon bags with the occasional bucket liner, a shorter sealer plus an iron for the big ones is a reasonable split. The overlapping pass technique works, it just needs care: overlap generously, and check the joins specifically.
Irons, Hair Straighteners and Other Improvisations
A heat sealing iron, or an ordinary clothes iron run along the bag mouth against a wooden board or a length of angle iron, produces a perfectly serviceable seal. This is how a lot of long term storage got packed before dedicated sealers were cheap, and it remains the fallback when a bag is wider than the machine you own.
A flat hair straightener also works on small bags and is the tool people reach for when sealing a quart bag on a kitchen counter. It is slow, the seal band is narrow, and it is not what you want for a bucket liner, but for a handful of spice bags it does the job without another purchase.
The Handheld Sealer and Cutter
Small battery or mains powered handheld sealers, often sold with a cutter blade, are aimed at exactly this middle ground. They are portable, they handle small and medium bags, and the cutter is genuinely useful when you are resealing a bag you opened. Expect a narrower seal band than a bench impulse sealer gives.
Comparing the Sealing Tools
| Tool | Best for | Seal quality | Watch out for |
|---|---|---|---|
| Bench impulse sealer | Regular sealing, any bag size up to the bar length | Consistent, wide, repeatable | Duty cycle; budget units fade on long runs |
| Heat sealing iron or clothes iron | Oversized bags and occasional use | Good with a firm straight edge behind it | Uneven pressure leaves thin spots |
| Handheld sealer with cutter | Small and medium bags, resealing | Narrow band, fine for shelf bags | Not the tool for 5 gallon liners |
| Hair straightener | Quart bags in a pinch | Narrow and slow but workable | Low, uneven heat on thick laminate |
Every option here is doing the same thing, which is melting the inner layer of the laminate against itself. The differences are consistency, width of the fused band, and how much bag you can do at once.
Sealing Technique That Prevents Failures
Work in an order: fill the bag, leave several inches of empty bag above the food, drop the oxygen absorber in last, squeeze out the loose air, then seal immediately. Absorbers begin working as soon as they meet air, so the bag they belong in should be the one you close next rather than the fifth one down the line.
Seal across the full width in one clean line, then look at what you made. A good seal is a uniform band with no bubbles, no wrinkles crossing it and no unfused patches. Tug it gently. If any part peels, cut below the seal and do it again rather than convincing yourself it is probably fine.
Leave Room to Reseal
Seal high on the bag rather than close to the food. That leaves you enough material to cut below the old seal and reseal the bag after you open it, which turns a single use bag into one you can reuse two or three times. It also keeps the seal line away from any grain dust that settled at the top.
Frequently Asked Questions
Can I seal mylar bags with a FoodSaver? Not by vacuum. A household vacuum sealer cannot pull air through smooth walled mylar, though some machines will heat seal a mylar bag placed in the sealing strip without vacuuming it. Check your model’s manual, and expect a narrower seal band than an impulse sealer gives.
What size impulse sealer do I need? At least as long as the flat width of your widest bag. Gallon bags are handled comfortably by a short bench sealer, while 5 gallon bucket liners want a long bar or an iron.
How do I know the seal is good? Look for an even band with no wrinkles crossing it, then pull it apart gently with your fingers. Any peeling, bubbling or unfused stretch means cutting below it and resealing.
My impulse sealer stopped sealing properly after a lot of bags, what happened? Most likely heat. Budget units are not built for continuous work, and the element and the PTFE tape over it degrade as they get hot. Let it cool between batches, replace the tape when it browns, and buy a heavier machine if you seal in volume.
Can I use a clothes iron? Yes, run along the bag mouth against a straight wooden or metal edge. Keep the motion steady, since pausing scorches the laminate and moving too quickly leaves a weak line.
Should I seal above or below the zipper? Above it, so the zipper is inside the sealed portion and stays usable after you cut the bag open. Sealing below the zipper wastes the feature you paid for.
The Bottom Line
An impulse sealer sized to your widest bag is the right purchase for anyone doing this more than once, with a heat sealing iron kept back for oversized bucket liners. Keep the seal line clean, drop the absorber in last, and check every seal by hand before the bag goes into a bucket. The tool is only half of it: see the mylar bags guide for thickness and sizing, and the oxygen absorbers guide for what goes in with the food.