Mylar is a metallised polyester film developed in the 1950s. Among its many qualities are reflectivity and gas and aroma barrier protection, making it perfect for storage. Mylar can be thought of as a metallic film that blocks light and air, protecting the contents and providing barrier protection from the external environment.
Mylar bags are made from Mylar film, sealed on three sides, the fourth can be easily sealed with a normal domestic iron, or heat-sealer, once the bag has been filled. Mylar bags are also available with zip-lock seals. Zip-lock Mylar bags provide excellent light and air barrier protection, and are ideal for short and medium-term food storage. For long-term food storage, all Mylar bags, including zip-lock bags, should be sealed with an iron or heat-sealer.
At this point it’s important to explain that short-term food storage for our purposes means less than one month, medium-term means one to six months, and long-term means more than six months. Many people have successfully stored dry foods for more than ten years using Mylar bags.
Once you’ve filled your Mylar bag, it’s best to remove as much oxygen as possible. You can push out most of it with your hands on a flat surface, but some oxygen will remain. This is where oxygen absorbers are used. An oxygen absorber is a small packet that effectively removes all oxygen from a sealed environment, such as a Mylar bag. Within each small packet is iron powder (Fe) and lesser amounts of other inert chemicals such as salt (NaCl) and calcium oxide (Ca(OH)2). The iron reacts with oxygen in the bag, producing iron oxide (FE2O3), and thus removing free oxygen (O2).
Oxygen absorbers are used in food packaging to prolong the shelf-life of foods. Eliminating oxygen means that aerobic bacteria and fungi are unable to grow.
Oxygen absorbers come in many different sizes. There’s a mathematical formula to establish the size of absorber, measured in cubic centimetres (cc), suitable for the size of bag you use. To keep it simple, 300cc absorbers are large enough for all Mylar Shop bags up to and including the 25cm x 40cm zip-lock bag and 2,000cc oxygen absorbers are ideal for our 35cm x 50cm, 48cm x 74cm and heavy duty 48cm x 74cm bags. 50cc absorbers are easily large enough for use with our 7.5cm x 10cm and 9cm x 10cm pouches, and our 10cm x 15cm ziplock bags, which are available in both silver and black colours. 100cc absorbers are large enough for use with our 12cm x 20cm ziplock bags, and our small 15cm x 15cm bags.
Using a larger oxygen absorber won’t do any harm; it’s just more cost effective to use the optimum size absorber for the bag you’re sealing. You could also use 7 of our 300cc oxygen absorbers in a 48cm x 74cm bag, for a total of 2,100cc, but it’s cheaper and easier to use one 2,000cc oxygen absorber.
Once you’ve added the oxygen absorber to your bag, simply press out excess air on a flat surface, and then seal the bag by applying firm pressure with your iron, or heat-sealer, to the unsealed edge of your Mylar bag. The ideal sealing temperature depends on the thickness of the bag, but is generally 160C-170C (320F-338F) for 3.5mil Mylar bags, and 190C-220C (374F-429F) for 7.0mil Mylar bags. Trial and error is the best way to find the correct sealing temperature for the bag you are using.
You can store the sealed bag in a plastic tub for extra protection from damage to the bag. Whether this is necessary depends on the environment in which you store your food. You would need to use plastic tubs if your bags were stored in a garage or shed, for example, to protect it from pests and human interference. If stored on a shelf inside the home, plastic tubs are unnecessary.
Check out the YouTube videos below for a step-by-step guide to using Mylar bags and oxygen absorbers for food storage. If you have any questions, please contact us and we’re happy to give you the benefit of our experience.
Sealing a medium Mylar bag with a clothes iron
Sealing a large Mylar bag with a clothes iron
Sealing a Mylar bag with hair straighteners
French language video on using Mylar bags
Check out the Full Range of Mylar Bags sold in Mylar Shop!
