How to Seal Mylar Bags, Steps and Mistakes

Last updated: June 4, 2024.
Writen by :
Eric Lu
Marketing at Bagnpouch

Mylar bags have become an essential tool for food storage due to their exceptional durability and protective properties. Composed of layers of plastic and aluminum foil, these bags are light-proof, air-proof, and waterproof, making them ideal for preserving the quality and freshness of food over long periods.

Whether you're a prepper, bulk food buyer, or retailers, sealing Mylar bags correctly is crucial to ensure your food remains safe and consumable.In this blog, we will provide a detailed guide on the steps for sealing Mylar bag and highlight common mistakes to avoid to maximize the effectiveness of your food storage efforts.

Step-by-Step Guide to Sealing Mylar Bags

  • Step1: Preparing to Seal Mylar Bags.
  • Step2: Filling the Myalr Bags.
  • Step3: Sealing the Mylar Bags.
  • Step4: Checking the Mylar Bag Seal.
  • Step5: Cool and Store Mylar Bag.

Preparing to Seal Mylar Bags

Before you begin, make sure you have all the necessary materials within reach.

High-Quality Mylar Bags: Mylar bags come in various sizes and thicknesses to accommodate different storage needs.

  • Smaller mylar pouches are perfect for spices and small quantities of food, while larger mylar pouches are ideal for bulk storage of grains, beans, and other staples.
  • Thicker bags offer enhanced "durability" and protection against punctures and tears.

Oxygen Absorbers: These are vital for removing residual oxygen from the bag, which helps in preserving the food's freshness and extending its shelf life. The size and number of oxygen absorbers needed will depend on the size of the Mylar bag and the type of food being stored.

Heat Sealer option: The heat sealer is a specialized device designed to create an airtight seal on Mylar bags.

  • Impulse Sealer: This type of sealer is user-friendly and effective for sealing Mylar bags.
  • Constant Heat Sealer: Offers a continuous heat source for a secure seal.
  • Vacuum Sealer: Some vacuum sealers come with an attachment for sealing Mylar bags, providing an airtight seal.
  • Clothes Iron: A common household item that can be used to seal Mylar bags by running it across the top edge.
  • Hair Straightener: Another household tool that can be used for sealing, especially for smaller bags.

Optional Materials: Bucket for Stability:

  1. Bucket for Stability: Using a bucket can help keep the Mylar bag upright and stable while you fill it with food. This is especially useful for larger bags and bulk storage.
  2. Permanent Marker for Labeling: Labeling your Mylar bags with the contents and the date of storage is essential for organization and tracking. A permanent marker ensures that the labels remain legible over time.

Filling the Myalr Bags

Filll Mylar Bags

Place the Bag in a Bucket

For added stability, especially when dealing with larger bags, place the Mylar bag inside a bucket. This will help keep the bag upright and make it easier to fill.

Add Contents

Fill the Mylar bag with the desired product, such as grains, coffee beans, or spices. Be sure to leave some space at the top of the bag to allow for sealing.

Add Oxygen Absorbers

Just before sealing, place the appropriate number of oxygen absorbers inside the bag. The amount needed will depend on the size of the bag and the type of food being stored. Oxygen absorbers are crucial for removing residual oxygen, which helps in preserving the food's freshness and extending its shelf life.

Remove Excess Air

Gently press the Mylar bag to expel as much air as possible. Start from the bottom and work your way up to the top. This step is essential to create a tight seal and prevent air from entering the bag after sealing.

Sealing the Mylar Bags

There are several sealing options available, each with its own set of advantages and disadvantages. The most common methods include using a constant heat sealer, clothes iron or hair straightener, impulse sealer, and vacuum sealer. Understanding the differences between these options can help you choose the best method for your specific needs.

Heat Seal Mylar Bags

Using a Constant Heat Sealer

A constant heat sealer provides a continuous heat source, making it ideal for sealing thicker Mylar bags.

How to Use:

  1. Set the constant heat sealer to the appropriate temperature, typically between 30°-550°F.
  2. Place the open edge of the Mylar bag between the heated jaws.
  3. Apply steady pressure to create a secure seal.


  • Provides a consistent and reliable seal.
  • Suitable for sealing thicker Mylar bags.
  • Adjustable temperature settings for different materials.


  • Can be more expensive.
  • Requires a power source.
  • Best for thick materials; cannot seal polyethylene.

Using an Impulse Sealer

An impulse sealer is a user-friendly device that provides a quick and reliable seal for Mylar bags. The heating jaws provide instant sealing in a small seal zone, ideal for occasional use.

How to Use:

  1. Adjust the temperature and time settings according to the manufacturer’s instructions, typically between 375-425°F.
  2. Place the open edge of the Mylar bag between the sealing bars.
  3. Press down to seal the bag, ensuring a tight and secure closure.


  • User-friendly and safe for sealing Mylar bags by manually.
  • Use power intermittently and heat the sealing jaws instantly, without requiring warm-up time.
  • Provides a quick and reliable seal.


  • Requires a power source.
  • May need adjustments for different bag thicknesses.
  • It may create inconsistent seals as done manually.

Using a Vacuum Sealer

A vacuum sealer not only seals the Mylar bag but also removes air, providing an airtight seal that is essential for long-term storage.

How to Use:

  1. Place the open edge of the Mylar bag over the vacuum port.
  2. Press the start button to extract air and seal the bag.


  • Removes air from the bag, providing an airtight seal.
  • Ideal for preserving the freshness of food.


  • Not all vacuum sealers are compatible with Mylar bags.
  • Can be more expensive than other sealing methods.
  • A little expensive but highly effective for long-term storage.

Using a Band Sealer

A band sealer is an efficient option for sealing a large number of Mylar bags, as it contains both heating and cooling elements and includes a small conveyor to pull the bag through the sealing mechanisms.

How to Use:

  1. Set the band sealer to the appropriate temperature and speed settings.
  2. Place the open edge of the Mylar bag on the conveyor belt.
  3. The conveyor will pull the bag through the heating and cooling elements, creating a secure seal.


  • Able to complete sealing work on a large number of bags.
  • Contains both heating and cooling elements for a reliable seal.
  • The small conveyor automates the sealing process, increasing efficiency.


  • Can be more expensive and requires more space than other sealing methods.
  • Requires a power source.

Using a Clothes Iron or Hair Straightener

Using a Household Iron sealing mylar bag

A clothes iron or hair straightener is a cost-effective and accessible option for sealing Mylar bags, especially for those who do not have a dedicated sealer.

How to Use:

  1. Set the device to medium-high heat.
  2. Clamp the open end of the Mylar bag.
  3. Run the device across the top 1 inch of the bag, ensuring a consistent and airtight seal.


  • Common household items that are easily accessible.
  • Cost-effective solution.


  • May not provide as consistent a seal as dedicated sealing machines.
  • Requires careful handling to avoid damaging the bag.

Checking the Mylar Bag Seal

After the process of sealing Mylar bags, it's crucial to ensure that the seal is airtight. A proper seal is vital to protect your food from moisture, light, and air, which can compromise the quality and longevity of your stored items. Here’s how to check the seal effectively

  1. Tug on the Sealed Area: Gently tug on the sealed area of the Mylar bag to confirm it is secure. The seal should hold firmly without any signs of separation or weakness.
  2. Inspect for Gaps: Visually inspect the seal for any gaps or incomplete sections. Even a small gap can allow air and moisture to enter, which can spoil the contents over time.
  3. Reseal if Necessary: If you find any gaps or if the seal is not airtight, reseal the bag. Use your chosen sealing method to go over the area again, ensuring a complete and secure seal.

Cool and Store Mylar Bag

It's important to allow the seal to set properly and then store the bags in optimal conditions to ensure the longevity and safety of your stored food.

Cool the Sealed Edge

Once you have sealed the Mylar bag, allow the sealed edge to cool for a few seconds before handling the bag. This ensures that the seal sets properly and becomes secure. Handling the bag too soon can compromise the integrity of the seal.

Label Information Required

Before storing, make sure to label each Mylar bag with the following information:

  • Contents: Clearly write what is inside the bag.
  • Date of Storage: Note the date when the bag was sealed. This helps in tracking the age of the stored food and managing your inventory effectively.
  • Expiration Date: If applicable, include an estimated expiration date based on the type of food and storage conditions.

Store the Sealed Mylar Bags

  1. Choose a Storage Location: Store the sealed Mylar bags in a cool, dark place. Exposure to light, heat, and fluctuating temperatures can degrade the quality of the food and the Mylar material over time.
  2. Use Food-Safe Buckets: For added protection, place the sealed Mylar bags inside food-safe buckets. This provides an extra layer of defense against pests, physical damage, and environmental factors. Buckets also make it easier to organize and store multiple bags.

By following these steps, you can ensure that your Mylar bags remain sealed and the contents stay fresh and safe for long-term food storage.

What Are Common Mistakes to Avoid When Sealing Mylar Bags?

Sealing Mylar bags is a crucial step in long-term storage, but there are several common mistakes that can compromise the effectiveness of your efforts.

Avoiding these pitfalls will help ensure that your item remains fresh and safe for extended periods, especially for the food products.

Choosing the Wrong Size Mylar Bag

One of the most common mistakes is selecting the wrong size Mylar bag for your storage needs. Using a bag that is too large or too small can lead to inefficient use of space and potential sealing issues.

What Thickness of Seal Should Be Used?

The thickness of the seal is crucial for ensuring the bag remains airtight. Impulse sealers typically offer 2mm, 5mm, or 10mm seals. For Mylar bags, a 5mm seal is generally recommended, while an 8mm or greater seal is often required to prevent the bag from bursting

Overheating the Mylar Bag

Overheating the Mylar bag can cause the material to burn or weaken, leading to compromised seals. It's essential to use the correct heat setting and duration to avoid this issue.

What Is the Ideal Temperature to Seal a Mylar Bag?

The ideal temperature to seal a Mylar bag varies with its thickness. For 3.5mil Mylar bags, the temperature should be between 320°F and 338°F (160°C and 170°C), while for 7.0mil bags, it should be between 374°F and 429°F (190°C and 220°C)

Overstuffing the Bag

Overstuffing the Mylar bag can lead to uneven seals and potential leaks. It's important to leave enough space at the top of the bag for sealing.

How Much Space Should Be Left at the Top?

For best results, fill the Mylar bag to about 2/3 to 3/4 of its volume. This allows enough room for a proper seal without overstuffing.

Incomplete Seals

Incomplete seals are a common issue that can allow air and moisture to enter the bag, compromising the stored food. Ensure the entire edge is sealed without gaps.

Double-check the seal by pressing gently on the bag. If you notice any gaps or weak spots, reseal the bag to ensure it is airtight.

Improper Use of Oxygen Absorbers

Using the wrong amount or type of oxygen absorbers can affect the effectiveness of your food storage. It's crucial to use the correct quantity based on the size of the Mylar bag and the type of food being stored.

How Much Oxygen Absorber Should Be Used According to the Different Sizes of Mylar Bags?

The amount of oxygen absorber needed depends on the size of the Mylar bag and the type of food being stored. Here are some general guidelines:

  • 0.5 US pt (240 mL) bag: 50cc
  • 1 US pt (470 mL) bag: 100cc
  • 1 US qt (950 mL) bag: 300cc
  • 1 US gal (3.8 L) bag: 500cc
  • 5 US gal (19 L) bag: 1500cc


Sealing Mylar bags correctly is essential for effective long-term food storage. Throughout this guide, we've covered the critical steps and common mistakes to avoid to ensure your food remains fresh and safe for extended periods.


  1. Preparation: Gather materials, label bags with contents and date.
  2. Filling the Bags: Use a bucket for stability, fill with food, and add oxygen absorbers.
  3. Sealing the Bags: Choose the right sealing method (constant heat sealer, clothes iron, hair straightener, impulse sealer, vacuum sealer, or band sealer) and follow proper procedures.
  4. Checking the Seal: Ensure the seal is airtight by inspecting and resealing if necessary.
  5. Cool and Store: Let the seal cool, then store bags in a cool, dark place, preferably in a food-safe bucket.
  6. Common Mistakes to Avoid: Avoid wrong bag sizes, overheating, overstuffing, incomplete seals, and improper use of oxygen absorbers.

We hope this guide has been helpful. If you have any questions about Mylar bag packaging, feel free to ask in the comments or contact us directly. We're here to help! 

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