How To Seal Mylar Bags With Clothes Iron? Mylar is a strong, multi-layer film (often comprising polyester and metal foil layers) that offers excellent barrier protection—preventing light, moisture, and oxygen from degrading stored goods. However, that protection only works if the bag is hermetically sealed. A poor seal will allow air or moisture to seep in, defeating the purpose of long-term storage.
Sealing Mylar correctly is especially important for food storage, emergency prep, seed storage, freeze-dried goods, or any items you want to preserve for years. Improper seals are a common reason stored items spoil or degrade prematurely.
A clothes iron is one of the more accessible tools for sealing Mylar bags when you lack a dedicated heat sealer. It can work well—if used properly and with care.
Tools & Materials You’ll Need
Before you start, gather these items:
| Item | Purpose / Notes |
|---|---|
| Clean Mylar bags | Choose appropriate thickness (3.5 mil, 5 mil, 7 mil, etc.) |
| Clothes iron | Preferably with temperature controls |
| Flat, heat-resistant surface (like wood, or a board) | To support the bag while sealing |
| Aluminum foil (optional) | To protect the iron plates from adhesive / residue |
| Oxygen absorbers (for food storage) | Helps remove remaining oxygen inside bag |
| Scissors or cutter | To trim excess bag top after sealing |
| Marker / labels | To write contents and date |
One source recommends setting your iron to a “wool” setting for good results—one or two passes across the edge usually suffice without damaging the bag.
Another more specialized site describes laying the open end of the filled Mylar bag over a bucket and using a clothes iron (or a Eurosealer) to seal it shut.
Because different Mylar thicknesses require different heat levels, testing on a scrap is always wise.
Step-by-Step: How to Seal a Mylar Bag with an Iron
Here’s a recommended procedure, based mainly on sealing best practices and combining multiple sources:
Step 1: Fill & Prepare the Bag
- Fill the Mylar bag with your items (e.g. food, grains, etc.), but leave 4-5 inches of empty top space. Overfilling makes sealing harder.
- If using oxygen absorbers, insert them last—just before sealing. Be quick; exposure to air reduces their effectiveness.
- Press out excess air from the bag manually, flattening content to reduce voids. This helps ensure a clean, even seal.
Step 2: Set Up Your Sealing Station
- Place a solid, heat-resistant board (such as a piece of wood or a countertop) as a base.
- Optionally wrap the board in aluminum foil or a thin cloth to protect it.
- If desired, put a thin aluminum foil layer between the iron’s plate and the Mylar edge to prevent adhesive from sticking to the iron.
Step 3: Heat & Seal the Bag Edge
- Plug in the iron and allow it to reach the target temperature (wool or medium-high, depending on thickness).
- Take the top edge of the Mylar bag—you should have front and back layers aligned—and press the iron down evenly for 1–3 seconds.
- Move the iron along the seam in a continuous strip (slightly overlapping seal areas). You may need two passes in thicker Mylar.
- Avoid lingering too long in one spot; overheat can burn or melt the Mylar layers.
Step 4: Inspect & Reinforce
- After initial sealing, let the seal cool for a few seconds.
- Gently tug the sealed edge to check for weak spots or gaps.
- If any part seems not fused, reapply the iron over just that section to reinforce it (overlapping with a good seal).
- Trim any excess top material if needed, leaving a small margin above the seal so the bag handles stress well.
Step 5: Cool & Store
- Once sealed properly, allow the entire bag to cool fully before handling it further.
- Label the sealed bag with contents and date.
- Store in a cool, dry, dark place. Many preppers place Mylar bags inside food-grade buckets for extra protection.
A well-sealed Mylar bag may shrink slightly as oxygen absorbers remove residual air—don’t worry if it looks vacuum-packed the next day.
Tips, Common Mistakes & Troubleshooting
Sealing with an iron has its caveats. Here are key tips and pitfalls to watch:
Proper Heat Level
- Too low: seal won’t bond, resulting in weak or leaky seams.
- Too high / too long: you risk burning or melting the Mylar foil layer, creating holes or weakening structure.
- Use the wool or medium setting on many irons as a starting point.
Consistent Pressure & Speed
Maintain even pressure and steady motion. Jerky movement or uneven strokes may result in incomplete seals.
Avoid Overlapping Seals Too Deeply
While overlap is good for reinforcement, pressing too many layers thick can prevent heat from penetrating and bonding properly.
Protection of Iron Surfaces
Some users wrap foil to protect the iron plates from sticky adhesives or melted bits.
Test First on Scrap
Always try on a leftover Mylar seam or scrap before sealing your actual filled bag. It helps set your heat/duration preferences.
Watch for Gaps & Micro-Leaks
Even tiny gaps can let air in. Check the seal carefully and reinforce problem segments.
Thickness & Mylar Type
Heavier Mylar (e.g. 5 mil, 7 mil) requires more heat or slower passes than thin bags. For very thick Mylar, a dedicated impulse or constant heat sealer may outperform an iron.
Some users report success sealing 7mm Mylar with a basic garage-sale iron on the “wool” setting.
Don’t Delay After Opening Oxygen Absorbers
Oxygen absorbers should be kept sealed until you’re ready to insert them. Once exposed, they begin absorbing oxygen and lose effectiveness.
Work Quickly
Because oxygen absorbers and contents may degrade over time in air, limit time between filler, absorber insertion, and sealing.
Avoid Punctures Near Seal
Be careful that the contents near the top aren’t sharp (broken grains, hard seeds) which could press against the seam and cause micro-leaks.
When a Clothes Iron Sealer Isn’t Enough: Alternatives
While a clothes iron is a useful fallback, there are better tools when dealing with many bags, thick Mylar, or long-term storage:
- Impulse sealer: fast, controlled heat bursts optimized for bag sealing.
- Constant heat sealer / bar sealer: provides continuous heated jaws—better for larger or thicker bags.
- Vacuum sealer with heat seal function: extracts air and seals in one operation (if compatible).
- Band / conveyor sealers: for high-volume sealing operations.
- Heat sealing machines for packaging (designed for Mylar / polyester films)
These tools deliver more consistent temperature, stronger seals, and are less risky to your iron or bag.
Conclusion
Using a clothes iron to seal a Mylar bag can be an effective, low-cost method—especially for small batches or home use—if you follow best practices:
- Preheat your iron to the correct setting (wool/medium).
- Work on a stable, heat-safe surface.
- Use steady, overlapping passes.
- Inspect, reinforce, and allow cooling.
- Use oxygen absorbers and label properly.
- Test on scrap first, and avoid overheating or uneven pressure.
For occasional or emergency use, the iron method works. For repeated or large-scale sealing, investing in a proper sealing device will give better reliability and reduce risk of failed seals.
