Testing Oxygen Absorbers

The other day I found some oxygen absorbers that had been shoved to the back of a cupboard and forgotten.  I think that they were about 3 or 4 years old.  They were sealed only with the temporary clips that are normally used for short periods during canning operations.  Being curious I decided to test them.

The normal way you test them is to tape them to the inside bottom of a quart jar.  The jar is then turned upside down in a pan of water.  Over the next 24 hours, the vacuum they create should cause the water to rise approximately 2 inch up into the jar.

As you can see from the pictures, these failed miserably.  Oxygen absorbers normally contain powdered iron and a salt.  The oxygen is used up when the iron oxidizes or rusts.  I took a couple of the failed ones and cut them open.  You will notice in the picture below that the iron has turned to reddish brown rust.  In a new absorber the iron will bright and shiny.

Howard

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5 Responses to Testing Oxygen Absorbers

  1. Peter says:

    There’s no way that a brand-new oxygen absorber could “cause the water to rise approximately 2 inch up into the jar”.

    First, oxygen accounts for only about 21% of the air, so removing ALL the oxygen in the jar wouldn’t draw up the water level by 30% or so.

    Second, an oxygen absorber doesn’t make the oxygen disappear. It rusts (oxidizes) the iron in the absorber, and as we all know from observing rusted iron objects, the rust is larger than the iron was. If just one cubic inch of oxygen was absorbed, the absorber would become much larger.

    In reality, oxygen absorbers can’t absorb very much oxygen, which is why they don’t appear to change size significantly as they work.

    Oxygen absorbers aren’t very useful unless you’ve done something to remove most of the oxygen in your container before sealing it, for example by purging with nitrogen or carbon dioxide.

    • Jojo says:

      What you fail to consider is that when the oxygen combines with the iron, it occupies less volume then then it is in its O2 gaseous state.

  2. admin says:

    All I can say is try it, you will be surprised. Here is another link that explains the same method of testing oxygen absorbers. https://www.usaemergencysupply.com/information_center/packing_your_own_food_storage/checking_capacity_of_oxygen.htm
    Howard

  3. John says:

    We use oxygen absorbers in Mason Jars and they cause aq good vacuum seal.

    We don’t pull a vacuum on the jars, just put the food in and put the lid in place and wait.

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