A Beginners Guide to Desiccants

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The information in this article, A Beginners Guide to Desiccants, has been updated and incorporated into an all-new, enhanced article.

Understanding and Making Your Own Desiccants | Backdoor Survival

Survival Basics: Understanding and Making Your Own Desiccants





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A Beginners Guide to Desiccants — 19 Comments

  1. Thanks to Gaye & Ron for such a great article! I knew basically what desiccants were and what they were used for, but had never gone the extra step to what I needed to do with them.

  2. Great simple explanation of desiccants. Proper protection from moisture is important. To that end, combining our moisture barrier bags with a desiccant is one of the most efficient ways to protect your goods. No matter how effective a moisture barrier bag may be, there is always a possibility that a minute amount of moisture may seep in. The use of desiccants is a smart preventive measure for added protection.

  3. Gaye,
    Wow the timing for this article is awesome. We were just discussing this the other day, Thanks again for all you do, and thanks for info on this subject as well.

    • @Billy – I do not have personal experience with kitty litter but I did find this on Wikipedia:

      “Silica gel is also used as cat litter by itself or in combination with more traditional materials, such as clays including bentonite. It is trackless and virtually odorless. Purchasing silica in the form of cat litter can be an easy and cost effective way for retail consumers to purchase silica gel for use in other applications, such as maintaining the desired relative humidity in humidors, keeping tools or other materials rust-free in damp environments or long-term storage, and preserving dried food.”

      So I would say yes.

      — Gaye

  4. Desiccants adsorb water, not absorb water. This mechanism occurs on the surface of the materials, so you really did not need an entire cup when less material could have achieved the equivalent in surface area. Moreover, you did not account and report for the desorption of water in your cellar over the 40 days.

    • Dude, the adsorbtion occurs on a molecular level.. That means that the water molecules sit on the surface of the dessicant MOLECULES, not the surface of the pieces visible to the human eye. For the casual observer who isn’t using an electron microscope it would appear to be absorbed. For goodness sakes has anyone ever taken chemistry ?

  5. Thank you! Great article! So I should use coffee creamer inside coffee filters to save seeds? I am just learning all this stuff. Late getting on board prepping and trying to catch up with the world. thanks!

  6. Hi I realize this is an old article, but as a reference I thought I would mention this:

    DampRid is effective, but every time I’ve used it, in any application, it pulls and pools water. In other words, you have to leave it in a dish or etc. because very quickly you will have a dish full of water which needs to be poured off.

    So, while I find this to be a great product for very humid places like under the sink or in a closet, where I can check the container frequently and empty the water, I think this would be a terrible product for uses such as storing clothing or other goods, where you wouldn’t be able to easily or regularly check and empty out any collected liquid water.

  7. “Silica gel is a partially dehydrated form of polymeric colloidal silicic acid. Silica gel has an amorphous micro-porous structure with a distribution of pore opening sizes of roughly 3-60 angstroms. These interconnected pores form a vast surface area that will attract and hold water by adsorption and capillary condensation, allowing silica gel to adsorb up to 40% of its weight in water. Silica gel is extremely efficient at temperatures below 77°F (25°C) (see Figures 1 and 2), but will lose some of its adsorbing capacity as temperatures begin to rise, much like clay (Figure 3). Much of silica gel’s popularity is due to its non-corrosive, nontoxic nature and its having received US government approval for use in food and drug packaging.”

    Salt will be an excellent electrolyte for any free water and accelerate corrosion and galvanic activity…..

  8. And yet another application for sodium chloride: I would like to add it to my handcrafted potpourri to keep the botanicals crisp. In this application would it be best freely sprinkled into the potpourri mixture. Any guess at what rate?

  9. Boom! Had Ball calcium chloride in the pantry. Made some squares of cloth out of some old sheets about 12″ X 12″. Placed the cloth in a bowl. Emptied a container of calcium chloride onto the cloth. Bundled the cloth up and secured with a zip tie. 3 desiccants in 5 minutes. Placed each desiccant on top of an old plastic lid. Thanks!

    When using a calcium chloride desiccant do not allow it to touch any metal. Calcium chloride is very corrosive! Ask any farmer with water weighted tractor tires where calcium chloride is used as a anti freeze…many a rim has been rusted clean through by calcium chloride.

    Melissa, I don’t know the rate but I run a guest house and make sachets using a technique above. I’m thinking that a sachet made with come calcium chloride and potpourri might be useful in a entry way closet where damp cloths might be hung or perhaps a bathroom or kitchen under the sink to freshen and remove excess moisture. Just remember the corrosive nature of this compound.

    • Perhaps in some specialized applications but not within the context of what we are describing in this article. Definitely not when it comes to food storage, as an example.

  10. This article doesn’t seem to factor in the water already present in the tested materials.

    For example, the rice was very likely not manufactured in a facility that was very stringent with moisture controls. It was dehydrated to a level suitable for safe long-term storage, and nothing more. Further, while shipping and selling to you, it was likely not in a watertight package. And prior to using it for this experiment, had said packaging been opened or accessed for other uses, thus exposing it to moist open-air?

    As far as we can tell, there was already plenty of water in the materials not specifically prepared and packaged for the absorption of water from the air. The results of this test then? Quite inconclusive.

    I can tell you that if you were to take a cup of rice and heat it (much like it was suggested for the silica gel packets) in the oven or even microwave, the rice will come out quite a bit drier than when you put it in. While I don’t have a scale accurate enough to measure the weight, I would invite someone else to do so.

    I typically take about two cups of rice, microwave it for about two minutes (it will get VERY hot, don’t use a plastic dish or it may melt) stir it, and repeat for a total of about eight minutes. The first time I mix it, it sticks to the dish because it’s cooking in the moisture that’s already present. By the second stirring, it will start to release from the dish, shrink, and grow a more opaque white. By the third and final mixing, it’s extremely hot and releasing steam. Even at this point, there is still some water being released. To test this, place the hot rice in a sealed plastic baggie (you might want to wrap it in a paper towel so the bag doesn’t melt), and watch how quickly and thoroughly it fogs up.

    I would very much love to see a test that accounts for this factor, as it is in my opinions, one of the very biggest factors to water absorption – prior water content.


  11. best article on the subject I’ve ever read! thank you –constant battle with many may of my pantry goods in extremely humid Houston (even with A/C running)

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