How to Seal Mylar Bags With a Heat Sealer
If you're sealing more than a handful of bags, a heat sealer is the tool worth owning.
It does in one press what takes an iron careful technique: a clean, straight, airtight weld every single time.
Here's how to use one properly, and how to pick one that can actually handle Mylar.
How to Seal a Mylar Bag With a Heat Sealer
The process is fast once the machine is set:
- Fill the bag and add your oxygen absorber, leaving 3 to 4 inches of headspace.
- Press out the excess air.
- Lay the open top flat in the sealer's jaw, straight and wrinkle-free.
- Press down and hold for the dwell time (a few seconds for an impulse sealer, less for a constant-heat bar sealer).
- Release, let it cool, then test the seal.
That's it. The machine controls the heat and pressure for you, which is exactly why it's the most reliable method.
Why a Heat Sealer Is the Best Sealing Method
Here’s why this sealing method works the best:
Consistency is the whole reason
An iron depends on your hand staying steady and your heat staying even. A heat sealer removes both variables, every seal comes out the same.
It's also faster for volume, and it leaves a narrow, professional weld that's easy to test.
If you're building a serious supply or sealing regularly, the time it saves pays for itself.
Heat sealing works because the inner polyethylene layer of the bag melts and fuses to itself under heat and pressure, welding the two sides into one airtight bond.
Types of Heat Sealers for Mylar Bags
Not every sealer handles Mylar equally, so know what you're buying:
Impulse sealer
The most common home option. The heating wire warms only when you press, so there's no warm-up and no standby heat. Great for thinner bags and occasional use.
Constant-heat (bar) sealer
Stays hot the whole time. Better for thick bags and high volume, because the steady heat pushes through heavier material an impulse sealer can struggle with.
The seal bar on a vacuum machine
Designed for thin vacuum bags. It can seal thin Mylar, but often can't fully bond thick 7 to 15 mil bags. Test before you trust it.
Don't Skip the Seal Test
Even with a machine, confirm it worked. Let the seal cool, then tug both sides, they shouldn't separate. Squeeze the bag and listen for hissing air.
For the full testing method and the universal rules that apply to every sealing method, see our main guide on how to seal Mylar bags.
Common Heat Sealer Mistakes
- Too short a dwell on thick bags. Heavy Mylar needs a moment longer for the layers to bond. A quick press leaves a weak seam.
- Sealing too close to the edge. Leave a small margin so the weld has bag on both sides.
- Trusting a vacuum sealer on thick Mylar. It often won't fully bond, always test.
- Skipping the second pass on 12 mil and up. A double seal is cheap insurance on thick bags.
The Bottom Line
A heat sealer is the fastest, most consistent way to seal Mylar bags, especially at volume.
Match the sealer to your bag thickness, leave enough headspace, and run a double seal on thick bags.
Whatever sealer you use, it's only as good as the bags. Roylo Globe carries Mylar bags and oxygen absorber kits in every size and thickness, from quart bags to heavy 5-gallon bags, with absorbers and labels included.
Frequently Asked Questions
What kind of heat sealer do you need for Mylar bags?
An impulse sealer works for most home use and thinner bags. For thick 10 to 15 mil bags, a constant-heat bar sealer or a heavier-duty impulse sealer gives a more reliable bond.
Can you seal Mylar bags with a vacuum sealer?
Sometimes. A vacuum sealer's bar can seal thin Mylar, but it often can't fully bond thick bags. Test the seal before relying on it, and see our guide on vacuum sealing Mylar bags for that method.
How long do you press a heat sealer on a Mylar bag?
A few seconds for an impulse sealer on a standard bag, longer for thick bags. When the seam comes out flat and fused with no wrinkles, you've got the timing right.
Do you still need oxygen absorbers with a heat sealer?
Yes. The sealer closes the bag, but the oxygen absorber removes the air trapped inside, which is what protects the food long-term.