Survival Basics: Understanding and Making Your Own Desiccants

In 2013 when I first wrote about desiccants, the context surrounding the use of desiccants was a mystery to me.  I knew that little pillows of gel were frequently packaged with with electronic gizmos, new shoes, pill bottles and even clothing purchased over the internet.  I also knew that  many articles, books and websites with information about long term food storage also talked about desiccants.

As far as my knowledge of desiccants went, I was clueless. What are they?  How are they used?  And were they really necessary?   It seemed that depending upon who you consult, they were absolutely 100% necessary or a total waste of time and money.  Talk about being confused.

Understanding and Making Your Own Desiccants | Backdoor Survival

A lot of has changed since then.  I am more educated as is the prepper community as a whole.  I now know that a desiccant is to moisture what an oxygen absorber is to the oxygen in the air.  Sounds simple enough, right?

Three years later, it is time to update what we now know about desiccants and provide you with some easy peasy directions for making your own.  But first, what exactly is a desiccant?

What is a Desiccant?

Starting with its most basic definition, a desiccant is a substance that absorbs water. It is most commonly used to remove humidity that would normally degrade or even destroy products sensitive to moisture.

As an oxygen absorber is to air, a desiccant is to moisture. That means items that may be subject to mold and mildew if left unprotected in a damp area will be safe from those nasties if stored with a little pillow or packet of desiccant on board.

There are many types of desiccants.  Wikipedia gives us a lengthy list of desiccants but instead of burdening myself with figuring them out on my own, I asked my friend Ron Brown to share his knowledge of desiccants as well as the results of his experiments using various types of this magical stuff.

Here is some of what he has shared with me.

Some Common and Not So Common Desiccants

Silica Gel:  Silica gel is one of the more common desiccants.  Crafty types use it to dry flowers and in other projects.  As with other desiccants, as water evaporates from the flowers, it’s soaked up by the gel, thus drying them out for posterity.  Packets of silica gel are also found packaged with pills, over the counter remedies and vitamins.  What many people do not know is that these can be reused if you dry them out using low heat in the oven.

Understanding and Making Your Own Desiccants | Backdoor Survival

Salt:  Salt is a desiccant. If it cakes in the shaker and won’t come out, that means it’s soaked up moisture from the air and the little grains of salt have glued themselves together. To prevent caking, calcium silicate is added to table salt.

Rice:  Rice is added to salt shakers to keep the salt flowing freely. So if salt is a desiccant, maybe rice is an even stronger desiccant.

Calcium Chloride:  Ron told me that he totally ruined a pair of leather shoes once, spreading calcium chloride with a shovel off the back of a flat-bed truck (to minimize the blowing dust) back in his college-student, summer-job, road-construction days.

Cement and plaster of Paris:  Both cement and plaster of Paris are “calcined” at high temperature and will gradually harden if left setting around the in the garage. They absorb moisture from the air. They are desiccants.

Powdered Non-Dairy Creamer:  A bowl of powdered non-dairy creamer will gradually harden if left on the table unused.  Yes, scary as this sounds, non-dairy creamer is a desiccant.

Plasterboard or Wallboard:  Ever heard of a Kearney fallout meter?  When building a Kearny fallout meter to detect radiation, Kearney himself said you must have a desiccant in the cell to keep the atmosphere as dry as possible. In his original fallout-meter directions, he tells how to make a homemade desiccant from plasterboard. He recommended a piece of wallboard or plasterboard that has been broken into half-inch cubes and dried in the oven.

Unfortunately, it doesn’t work (Ron tried it). His guess is that “plasterboard” has changed over the years. No doubt builders prefer wallboard that does NOT soak up moisture compared to wallboard that does.

Which Desiccant is Right For You?

Now here is where things get interesting. Ron ran some experiments testing various types of desiccants and was kind enough to share the results and a tip for making your own desiccant packets.  Here, in his words, is what he had to say.

So which desiccant is best?

To answer that question, I took one cup each of silica gel, salt, rice, calcium chloride, plaster of Paris, and non-dairy creamer, poured them in separate bowls, then lined the bowls up on a table in the cellar. Relative humidity was in the 65-75% range. I weighed them in the beginning, gross and tare, and at the end of 40 days.

Understanding and Making Your Own Desiccants | Backdoor Survival

And the winner is . . .  Calcium chloride!

The net start weight of the calcium chloride – CaCl2 – was 224 grams. The net finished weight was 349 grams. So one cup of calcium chloride picked up 125 grams of water in 40 days, a gain of 56%. (It also doubled in volume.)

SIDE NOTE:  At the time I conducted this test I was aware that Cresson Kearny recommended against using calcium chloride as a drying agent in a Kearny Fallout Meter. He said, “Do not use calcium chloride” (see page 215 of “Nuclear War Survival Skills” by Cresson H. Kearny).  Pretty straightforward.  But he never said WHY and that puzzled me because calcium chloride is a top-drawer desiccant. Later on, I think I discovered why. After a couple of months in a continuously moist atmosphere, calcium chloride turns to a liquid. What part of “mess” don’t you understand?

Understanding and Making Your Own Desiccants | Backdoor Survival

The non-dairy creamer was first runner-up. One cup of non-dairy creamer picked up 20 grams of water, an increase of 16%.

None of the others (including the store-bought silica gel) picked up enough moisture in 40 days to measure. The silica gel had a net start weight of 225 grams and an end weight of 225 grams. That’s for 40 days. No doubt a year would tell a different story.

Even so, calcium chloride was the clear winner. Please note that a hard, half-inch thick crust had formed over the surface of the calcium chloride. The crust was almost like concrete, really quite difficult to chip away without breaking the dish.

So where can you buy calcium chloride? One place is in with the canning supplies, sold by Ball as “Pickle Crisp Granules” (5.5 oz. for $6). It makes the pickles crunchy and is used in commercial dills (Claussen, for example).

Understanding and Making Your Own Desiccants | Backdoor Survival

It’s cheaper to buy Morton Safe-T-Power ice melter in plastic cans, 9 lbs. for $5. People use it on their outside steps and sidewalks in winter to melt ice. If you buy pallets of calcium chloride in 50-lb. bags, you can get it for $12 a bag. Tractor-trailer loads are even less.

I put “packets” of desiccant in with my vegetable seeds.

Understanding and Making Your Own Desiccants | Backdoor Survival

I make the packets from coffee filters (Mr. Coffee-type), cutting, folding, and stapling as necessary. Don’t forget that calcium chloride can potentially double in volume from its original (dry) size. So don’t stuff the packets. More is not better.

Were I to use larger containers – 5-gallon buckets, say, or 30-gallon trash cans – for storing grains, flour, and the like, then I would not use fragile coffee-filter packets. I would use old vitamin bottles or mayonnaise jars (of whatever size seemed appropriate for the task at hand) with many small holes punched in the lid. Jars LABELED with what’s inside, thank you!

Understanding and Making Your Own Desiccants | Backdoor Survival

But whatever desiccant you choose and however you use it, it is crucial to the success of your storage program. Crucial, critical, important, essential, indispensable, all that stuff.

But Wait. There is More!

After posting the original article, Ron contacted me and owned up to a mistake.  It is best to let him describe his error/goof in his own words.

OPS! I made a mistake. As difficult as that may be to believe, my wife assures me that such a thing is possible. (But that’s what wives are for, eh?)

In the above comparison, I concluded that silica gel did not absorb enough moisture to measure. Turns out I didn’t use it correctly.

Silica gel contains “indicator” crystals. When blue, the gel is ready to go. When pink, the silica gel is already saturated with water vapor and won’t pick up anything further.

And that’s what I (mistakenly) did in my comparison. I used silica gel that had been setting around for a long time and had pink indicator crystals. After discovering my error, I dried the gel in the oven at 250 F for 45 minutes. The pink crystals turned back to blue and we were ready for business.

THEN I compared silica gel to calcium chloride. After four days, they had both gained 14% of water weight. The silica gel topped out shortly thereafter. At the end of eight days, the silica gel had gained 18% and the calcium chloride, 50%.

Depending on your application, silica gel has a nice feature in that it remains granular, pourable like sand, even when saturated. Calcium chloride cakes into one solid lump.

The Final Word

One really good use of a desiccant is to store one with the vegetable and herb seeds we save at the end of each growing season.  In addition, depending on your climate and packaging techniques, it may not be a bad idea to include a desiccant in with the grains and bulk foods we hope to store for months, years, or even decades. Just know that a desiccant will moderate and maintain the moisture content of stored food; it will not change or alter the moisture content in the food itself.

In closing, I want to thank Ron for his help in educating me relative to the use of desiccants as well as his experiments and methodology for creating DIY desiccant packets.  Who would have guessed that coffee filters and a bit calcium chloride or non-dairy coffee creamer would be so useful?

Additional Reading:  35 Reasons Coffee Filters are Survival Multitaskers

Finally, I would also like to put in a plug for Ron, who is the author of The New 2000-Hour Flashlight as well as the Non-Electric Lighting Series of print books and eBooks.  Each of his books are chock full of information that is not only useful, but a darn interesting read as well.

Enjoy your next adventure through common sense and thoughtful preparation!
Gaye

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[related-posts]

Bargain Bin: Thinking of making up your own packets of desiccant?  Here are some of the products that will get you started as well as other links related to this article.

Ball Pickle Crisp 5.5 oz. Jar: You can make up a large batch of desiccant packets with this tub of “pickle crisp” and some coffee filters such as the Brew Rite #4 Cone Coffee Filters.

DampRid Hi-Capacity Moisture Absorber, 4-Pound Tub:  This is Calcium Chloride. This stuff has been used by boaters for years and is a popular item.  Seems to me that a 4 pound tube, used to make desiccant packets, would last forever.

“Dry&Dry” Silica Gel Packets Desiccant Dehumidifiers:  These are 3 gram packets of  silica gel .  As a rule of thumb, use 3gm to 5gm per gallon.  Note:  these do not take the place of an Oxygen Absorber.

Mylar bags & Oxygen Absorbers: What I love about Mylar bags and oxygen absorbers is they protect against every single one of the food storage enemies. Prices do vary but for the most part, they are inexpensive and easy to keep on hand. And while you can seal them up with a FoodSaver, some tubing and a common clothes iron, I find it infinitely easier with a cheap hair straightening iron that you can pick up $20 or less.

60 – 300cc Oxygen Absorbers: This is one area where you want to make sure you are getting a quality product. Currently, a pack of 60 (in three 20 unit packs) is about $12 with free shipping.

Nuclear War Survival Skills:  Updated in 2012. this book by Cresson Kearny is based on the Cold War scenario of a major thermonuclear exchange between the Warsaw Pact and NATO. It provides an impressive range of nuclear survival techniques including how to: – Make your own radiation meter – Decide whether to evacuate – Construct your own fallout shelter – Keep your water safe from contamination It also includes detailed plans for six nuclear fallout shelters and two nuclear blast shelters. You can also download a free version of the 1987 edition by clicking this link.  It is not as richly illustrated and some of the newer chapters are missing.  Still, free is free.

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  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.

    1. @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.

    1. 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.

    1. 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.

    Michael

  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)

  12. Interesting testing, and lots of good info. I have a lot of little silica gel packets and my plan for recharging them post-SHTF is to use the SunOven with the lid only loosely closed. This should let them get warm enough to release the moisture without ruining them. Then I can store them in canning jars or ziplock freezer bags, whichever is most handy.
    I keep so many of the little packs because I plan on tossing a few into any opened #10 cans of FD food to keep moisture under control and extend the shelf-life of an opened can. With just two people eating from a can, it could take a few days to finish off the can and no need to risk spoilage.

  13. Gaye, VERY interesting article with lots of info! I understand using silica gel or other similar moisture absorbents if I were storing say grains in large mylar bags, but, if I vacuum sealed say 1 gallon bags with an oxygen absorber in each bag, would I still need to use a moisture absorber? There are so many possible scenarios, it’s hard to imagine a hard and fast rule.

    Thank you for sharing,
    Jose

    1. Oxygen absorbers won’t absorb useful amounts of moisture, and desiccants won’t absorb oxygen. So you’re better off using both when storing dry goods.
      Quick tip: put the desiccants at the bottom of the bag, fill it with product then put the oxygen absorber in just before sealing the bag. Oxygen absorbers actually need some moisture to do their thing, but desiccants take time to work so by separating them at the top and bottom of a bag, the oxygen absorber is finished before the desiccant has done its job fully.

  14. Have you ever heard of Damp Rid? This is your calcium chloride. They work great but, if you don’t drain them the liquid turns corrosive.

  15. Just wondering, my neighbor is the manager at a large facility that makes ice melt, I asked her if I could buy a 30lb bag of Calcium Chloride. She said sure, for 20 bucks.
    Can I use this, or is there different grade if this product, or anything special I should know before making my own oxygen absorbers?

    Thanks Johnny

    1. Do you mean desiccants? (Oxygen absorbers are something else completely.) I don’t see why not. Make sure it is packaged well (sealed) so that it does not contaminate your food items. For large areas, I like Ron’s idea of a lidded jar with holes poked into the lid.

  16. Another informative article! Have you done a similar article about making your own Oxygen Absorbers? If so, I guess I missed it. I would like to make my own Desiccants and Oxygen Absorbers to use in packing dry food for long term storage, i.e., rice, beans, etc. Also, the ratio of how much desiccant and/or oxygen absorber to use per pound of rice, for example, would be useful. I try to store dry foods in four serving portions. How much of each to a package would be very useful. Thank you for helping us all be better prepared…

  17. When I was in the US Navy, 78-84, the Powdered Non-Dairy Creamer packets were a solid piece… we would break them up and put them into our coffee cups before we poured the coffee into them and stir…

  18. Some types of kitty litter contain silica and work well to absorb moisture. For 20+ years, while living within a half-mile of the ocean in a sub-tropcal climate, I witnessed and experienced the ravages of salt air on various products all around me; and I wanted to protect certain of my expensive/ hard to replace items from that unnecessary fate. I enjoyed complete success using kitty litter to protect several valuable steel/iron items from corrosion in the following way:

    I poured the kitty litter about 1″ deep into some 10″ X 12″ baking pans and placed them on the floor of the large, sealed plastic bag enclosing my precious items. Any time I removed the items from the bag for use, I took the baking pans of kitty litter out of the bag and dried them in the oven at about 250F for an hour, which drove out any moisture that had been absorbed by the kitty litter. Every few years I replaced the kitty litter with fresh, after pre-drying it in the oven as described.

    Over-kill? Maybe…but it’s hard to argue with success.

    Also, I was just reminded that Japanese motorcycles and ATVs are packed in crates and shipped from Japan in ocean-going containers from Japan. Fairly large bags of dessicants are packed with the vehicle inside each crate. Dealerships uncrate those bikes and ATVs and regularly toss the dessicants. Ask nicely at your local dealership and you may be rewarded…

  19. nothing wrong with the craft style DIY packs – but a large commercial coffee filter tied into a sache bundle, with a wire tie gets the job quicker ….

  20. Not that it’s going to aid in survival or anything but another useful life hack for silica gel and other desiccants is that it can remove mold/mildew smell from cloth, paper and other porous materials by putting affected items in a sealed container with some silica packs for a few days (more smell more silica).

  21. Thanks for the research. I live in a tropical climate (with an average of 70-80% humidity but it hits 90-100% during rainy seasons, woohoo) and was looking for a more affordable / lasting alternative that’s easily purchased and environmental friendly since store bought dehumidifiers gets full in 2-3 weeks.

    I’m quite excited in using non-dairy creamer that i have lying around as a replacement. What are your thoughts on charcoal briquettes + rock salt?

    1. Unfortunately, any moisture-absorbing compound will “get full” sooner or later. The key to using any of these materials is to seal them inside a container, along with the item that is to be protected from moisture. They won’t keep your closet dry, or your basement, unless you have some schedule for regularly drying the compound (for example, baking it in your oven). For long-term sustainability, drying the desiccants might be a good use for excess solar energy, or maybe concentrated sunshine can be used to dry a batch of desiccant. If you’ve run an electric dehumidifier appliance, you’ve probably noticed that it can pull more than a liter per day from a single room (and that it draws a lot of electric power). A bag of chemical desiccant would have to absorb the same liter of water every day to create the same dry condition.

  22. Maybe the problem with using “plasterboard” (gypsum, chemically known as Calcium Sulfate) as a desiccant is that it must be de-hydrated at 400-450F (230C) (at standard atmospheric pressure) for two hours before it is effective. See https://secure.drierite.com/catalog3/page19b.cfm for discussion. Lower temperatures are ineffective, no matter how long you wait. This web site also describes the usefulness of combining anhydrous calcium sulfate with a small amount of calcium chloride to increase the water absorbing capacity, without the self-dissolving problem of pure calcium chloride.

  23. I know it’s been 2 years since this article, but well it showed up searching for potential desiccants.
    A more valuable test, imho, would have been to put the desiccants in a sealed pot, measuring the starting humidity, followed up by measurements to see what humidity the inside of the pot stabilizes at.
    Desiccants depend on relative humidity up to saturation, meaning that they tend to keep humidity in their surroundings at a certain level. You can even buy desiccant packs designed to keep a certain humidity level. Some stuff stores best at e.g. 60% humidity, other stuff much dryer.
    About the gel pack beads was it fresh or recycled from something you bought? If the latter it might have been saturated, did you reset the pack by drying in an oven before the test?

  24. What a great article thank-you.
    I have 2 900grams of dry pack moisture absorbent silica gel.
    Each winter I put my van in storage by covering it with a good tarp,make sure windows etc are closed tight. It is parked in the rain forest of the north west.
    Somehow the front and rear gets mildewed.
    What do you think would be a good way to handle this?
    Thanks so much. Rose

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