To seal Mylar bags with a clothes iron, set the iron to a high heat setting with steam turned off. Place the bag on a flat heat-safe surface, cover the opening with parchment paper, and press the iron firmly on the top edge for 3 to 5 seconds. Let the seal cool before checking to ensure it is airtight.
Sealing Mylar bags correctly can mean the difference between long-term protection from an airtight package and the slow leakage of air into the bag causing the loss of its contents. You can create an airtight professional seal when using a standard household clothes iron if you know how to use it. If you don’t yet own an impulse sealer, then this method can work just fine and is often used by small businesses and home packagers.
Why Use a Clothes Iron to Seal Mylar Bags?
Mylar's inner layers will bond together evenly when you apply heat evenly to them with an iron. The heat comes from the flat surface of the iron, and because there is enough pressure on each layer to cause them to melt, all of the layers will completely seal.
There are some common reasons to use this method:
- No special tools are needed
- Excellent for small batch production
- Great for testing package design at home or in a small business
- If you do it right, you can create a strong airtight seal
- A good option if your sealer fails
This method is easy and dependable for anyone who needs to test their package before they buy the tools for doing so.
If you want to explore additional sealing methods, zipper options, and professional techniques, see our complete guide on how to close Mylar bags.
"Heat sealing works because the inner sealant layer in a laminated pouch softens and bonds under controlled time, temperature, and pressure. Even a household iron can create a reliable seal if you apply consistent heat and compression across a clean, flat sealing area." - Dr. John R. Wagner Jr., Flexible Packaging Engineer
What You Need Before You Start:
The way you prepare before starting to seal your bags, is more important than actually doing the sealing process. When you prepare properly, you will avoid wrinkles, weak sealed edges and melting of the bags.
The tools and materials you will need include:
- A common clothes iron (do not use steam)
- A flat surface that is heat resistant
- A wooden board, book or a metal straight-edge
- Parchment or plain paper (highly recommended)
- Mylar bags that you have already filled
Do not use steam. Steam creates moisture and moisture will weaken a seal and can potentially ruin the contents inside of the bag (especially for food products and moisture-sensitive items).
Proper sealing is what makes Mylar effective at protecting contents. To learn more about how airtight Mylar bags really are, read our guide on are mylar bags airtight?
Sealing Mylar Bags with a Clothes Iron in Steps
1. Set the Proper Temperature
The temperature should be set to a high level, like Cotton or Linen in your iron’s settings. You need to have the iron on for a while so it warms up enough before sealing the bags. The best temperature to seal Mylar bags is about 350°F to 400°F.
You also need to turn off the steam function on your iron.
2. Prepare the Bag Opening
Be sure that the inside parts of the bag that will be sealing are completely clean; so there is nothing left on those areas like any particles of dirt or residue; or else they will prohibit you from sealing.
Smooth the sections of the bag to be sealed and remove any excess air that may be in the bag, if needed.
3. Place a Protective Layer Over the Area Being Sealed
Put a sheet of parchment or unprinted paper over the section that is going to be sealed. This will keep the iron from melting or sticking to the outside layer.
Doing this is strongly suggested when using printed or glossy Mylar.
4. Apply Heat and Pressure
Place the iron firmly on the section of the bag you want to seal for a period of 3 to 5 seconds. Keep applying pressure on the iron by holding it still as you seal the bag instead of moving it manually across the area to be sealed or pushing up and down.
If the bag is wide, you can seal separate sections until you have completely sealed it.
5. Allow Sealing to Cool Down
Let the seal cool down for up to 5-10 seconds before trying to touch the seal. The cooler you let the seal get before checking, the stronger the bond between the two bags will become.
If you find that after cooling the seal that the two sides of the seal separated, simply repeat the process with a little extra heat and/or pressure.
Pro Tips For Creating Stronger Seals
Making minor adjustments can result in significant improvements to the quality of your seals.
- In order to achieve additional protection you should seal the bag twice.
- When sealing your bag, use a hard surface (as opposed to carpet) to create a strong seal.
- Fill the bag no more than 50% full.
- Make sure to leave a minimum of 1/2 inch of space between your contents and the top of the bag.
- Before sealing, always test with an empty bag.
Many commercial packers use the above instructions even though they have impulse sealers.
Sealing works because the inner layer bonds while the outer layers block air and moisture. To understand the technology behind this, read our guide on how do mylar bags work?
Avoid These Common Mistakes
1. Excessive Movement
If the iron is moved excessively, wrinkles or uneven seams will be created when seals are formed.
2. Steam
Moisture will weaken all bonds and potentially damage a product.
3. Insufficient Temperature
A seal with insufficient temperature will result in a weak bond and when the seal is finished, it will peel apart.
4. Excessive Temperature
An excessive temperature will melt the bag or distorts the material.
It may take 1 to 2 test seals before you'll find an appropriate temperature and enough time to create a proper, permanent seal.
If you are sealing bags for long term storage, you may wonder how they compare to vacuum sealing. Our guide Are Mylar Bags Better Than Vacuum Bags? breaks it down.
When to Upgrade to a Heat Sealer
You should upgrade to a heat sealer if you package:
- Large Volumes Of Bags Each Week
- Require Consistent Sealing Within Tolerance Limits
- Use an Industrial Mylar That Is Thick
- Need A Production Rate That Is Faster Than Using An Iron
Impulsive heat sealers are perfect for scaling up operations since they provide professional-grade, clean, and efficient results in only seconds!
Can I Use a Clothes Iron to Seal Custom Mylar Bags?
Yes, custom Mylar bags are capable of being sealed by a clothes iron. The inner linings of both standard and custom Mylar bags are the same, in that they will bond to each other with heat and pressure. To get the best results, use high heat without steam, place parchment paper over the area where you will be sealing the bag, and press down with a fair amount of pressure. A few seconds should suffice.
If you have custom bags that are thicker or have a heavier coating, then you may need to use a little more time and/or pressure; however, the process described above will work for small quantities, personal sealing, and for testing out the type of packaging that is available before purchasing commercial sealing apparatus.
For more information on personalized mylar pouches, view our custom mylar bag examples.
A Short Overview
To seal Mylar bags using a household iron: Smooth the bag’s opening, apply a protective layer like paper, then press a hot iron across the seal area until the inner lining fuses shut. This method works well for food storage, packaging, and small batch sealing without a heat sealer.
In Closing
Using a clothes iron to close Mylar heat sealable bags is a great option if you have the proper temperature, pressure, and preparation for each bag; you can achieve a perfect seal that is very comparable to those made using professional industry sealing machines.
It’s ideal for home use, small businesses, testing new packaging ideas, or preventing you from needing to use any outside sources of help when you’re in emergency situations where you don’t have the tools needed for sealing bags.
If you package products often, investing in quality heat sealing equipment will save time and increase your ability to consistently create the same amount of seal every time you seal a bag. However, for a lot of occasions your basic household iron could work fine for sealing/packing products using heat.
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