There are quite a few misunderstood concepts about oxygen absorbers and Mylar bags because they were intended to be used commercially for product packaging under the guidance of a food technologist. Nowadays, directions for home use have mostly consisted of internet posts from those who have used them. For the most part the information on the internet is correct, but some incorrect things have been spread around the internet too.
True or False
Your Mylar bag will look vacuum-packed when the oxygen has been removed.
False. It is a very common misconception that the “vacuum-packed look” is a confirmation that the oxygen has been removed. This myth is probably why people seem to think some oxygen absorbers do not work. True, you often WILL see this effect, but if you don't that does not mean the oxygen removal process didn't work. Oxygen absorbers do not absorb air; they absorb oxygen, which is 21% of air. That means roughly 1/5 of the air volume will be gone but 4/5 of the air remains no matter how many oxygen absorbers are used.
True or False?
Thicker Mylar bags work best.
False. Thickness can relate to the physical strength of the bag, but our Mylar bags will hold weight of 2 cinder blocks over EACH square inch because it is “Biaxially Oriented” which makes a grid-like structure for remarkable strength that protects far better than other thicker bags.
True, 7 mil Mylar and other “extreme” thick Mylar bags relatively provide no more oxygen protection than 2 mil Mylar because it is only the aluminum on the surface that keeps the oxygen out. Also keep in mind that you will need a 600 watt sealer to seal Mylar properly that is 7 mil thick.
True or False?
You should check your new Mylar bags for leaks. Some may have small holes at a folded crease.
False. Mylar is one of the toughest flexible materials ever created but it is not metal. People are more familiar with a lower quality replica of Mylar that looks metallic because a separate layer of aluminum has been added.
True, Mylar is transparent. Normal use such as filling it or moving it will cause tiny breaks in the foil layer that you may sometimes see if you hold it to the light - but don't worry, they are not holes. This happens with all Mylar foil films and their barrier properties are not significantly affected.
True or False?
If Mylar bags fail the “flashlight” test than they are no good.
False. Mylar is transparent and metal has been added to the Mylar to increase its barrier properties. People in the past have wondered if light is going to damage their food and it is true that all forms of energy have some potential to effect matter. True, direct sunlight can have a noticeable effect, but inside a metalized bag in a cool, dark storage place, there is virtually no effect from light. Our gallon and quart Mylar bags are metalized through a process called vapor deposition whereby aluminum is sprayed onto the Mylar surface to make it a better oxygen barrier.When you hold them to the light, you can see through them. They still provide an excellent barrier and will keep food preserved for well over 25 years.