Intro: Inexpensive Desiccant
Look around your house.
How many things can you find stored around your house that react negatively to moisture?
Hooks and lures in your tackle box
Ammunition and firearms
The list goes on and on.
What you need is something that will absorb the water before it has a chance to negatively affect you valuable items.
Step 1: Keeping Things Dry
2 major types of desiccant are Calcium Sulfate and Silica Gel.
Drierite is the brand name and registered trademark of a variety of desiccants made from anhydrous calcium sulfate (gypsum).
After Drierite has been exposed to moisture, it can be regenerated by baking at 410°F / 210°C for an hour.
Silica gel is most commonly encountered in everyday life as beads in a small (typically 2 cm x 3 cm) paper packet. Silica gel absorbs water readily, making it useful as a desiccant.
After Silica has been exposed to moisture, the gel can be regenerated by heating it to 250°F / 120°C for two hours.
Difference in abilities:
Calcium Sulfate can absorb approx 10% of it weight in moisture before it become ineffective and needs to be replaced or recharged.
Silica can absorb 40% of it's weight before needing to be recharged / replaced.
Calcium sulfate is a general-purpose desiccant geared mainly toward laboratory use. It is chemically stable, non-disintegrating, non-toxic, non-corrosive, and does not release its absorbed water when exposed to higher ambient temperatures.
Silica gel is extremely efficient at temperatures below 77°F (25°C), but its adsorption capacity will decrease as temperatures begin to rise. Much of silica gel's popularity is due to its noncorrosive and non-toxic nature; some grades have received U.S. government approval for use in food and drug packaging.
Step 2: Comparison Shopping
Ebay - silica gel packets - 600 1gram packets (1.32lbs) - $20.99 $15.90/lb
Drierite.com - Drierite - 1lb $5.52
walmart - silica kitty litter - 4 lbs $4.32 - $1.08/lb
The individual silica gel packets are self contained so they are ready to use right away. Once they are used you throw them out.
the Drierite and the kitty litter come in a single large container and will need to be transferred to a different container relative to the size of the area that needs to be dried
Originally I was thinking of using stocking as the container to hold the desiccant. I was looking in walmart and found ankle stockings(10 pairs) for $6.68 These would be great if you need to do a large area or container, simply pour in the desiccant and knot off the stocking. Another idea, if you are handy with a needle and thread you can turn one stocking into several smaller satchels.
After attending a wedding reception for some friends, I was looking at the goody bag each guest got to take home I realized that the Organza bags full of candies would be a perfect for re-purposing. No sewing required.
In the walmart craft section is a package of 12 4"x6" organza bags for $2.75 (or you can get a 10 pack of 5"x7" organza bags for $1.38 from various vendors online if you don't mind waiting for them to come in the mail)
Step 3: Solution
The organza bags that I re-purposed are 2"x3" and easily accommodate 40 grams (1.3 ounces) of silica which will be sufficient for a 5 gallon container.
In case you are wondering a standard 50 cal ammo can has an interior area of approx 470 inches so 10 grams (1/3 ounce) of desiccant will be sufficient.
There is roughly 30 grams to an ounce
Gallons Cubic Cubic Grams Ounces Feet Inches Silica Silica
1.1 0.14 237 5 .167
2.1 0.28 476 10 .334
3.2 0.42 714 15 .5
6.2 0.83 1,428 30 1
12.5 1.67 2,856 45 1.5
18.7 2.5 4,284 60 2
25 3.33 5,712 90 3
37.4 5 8,568 135 4.5
50 6.66 11,424 180 6
Step 4: Testing the Solution - Absorbtion Quantity
According to the information I have found, silica should be able to absorb 40% of its weight before becoming saturated.
1 milliliter of water = 1 gram
I added 4 milliliters of water to 10 grams of silica.
The silica absorbed all of the water without a problem.
Step 5: Testing the Solution - Time Absorbtion in a Sealed Container
I added 5 grams (about 2 teaspoons) of silica to an organza bag and sealed it into a 5 cup (1.2 liter) container with an area of approx 108 cubic inches to see what kind of drying power it has.
I used a clear plastic container so I could see the readings without opening the container and adding more humidity to the atmosphere of the container.
I sealed the container at 11 am and the humidity percentage was at 68% according to my thermometer/hygrometer.
By 1:45 pm the humidity ion the container was down to 42%
at 3 pm the level had dropped to 38%
I let it sit for a 2 more hours before finally opening the container to get the "after picture" but it did not go down any further.
In the short time I ran the test the silica gained .02 grams of weight from the moisture absorbed. I used the silica straight out of the package so I have no idea how much moisture it has previously absorbed. but theoretically this silica could absorb 1.98 more grams of water before becoming saturated.
One fact to keep in mind is that if your container is airtight and you leave it closed it will stay dry indefinitely. Every time you open the container ( or if your container is porous) you are introducing more humidity to the environment, and eventually your desiccant will become saturated and will need to be replaced or recharged.