Compared to metal cans, glass jars are very stable, although they don’t take being banged around very well. The cardboard boxes the jars come in are well designed to cushion them from shocks. The box also has the added bonus of keeping out damaging light.
The major advantage of glass jars is that they are reusable, both jars and rings, with lids being the only part of the package that must be purchased new for every use. If you’re not using the lids to form a vacuum seal such as would happen when doing boiling water or pressure canning then even the lids can be reused.
When you get right down to the bottom line, it is seldom practical strictly in terms of dollars and cents to put up your own food in jars. When you count the cost of your equipment, including the jars, rings, lids and all the rest, along with a not inconsiderable amount of your personal time, the cost of purchasing or growing your produce, you’ll almost always come out ahead to buy food canned for you by the commercial canning industry. That said, forget about the strict bottom line and examine more closely why you want to put up your own food. For many, gardening is a pleasure and they have to have something to do with the food they’ve grown! There’s also the fact that for many, you simply cannot buy the quality of the food you can put up for yourself. The canning industry tries to appeal to a broad spectrum of the general public while you can put up food to your own family’s specific tastes. Home canning is not so much about saving money as it is about satisfaction. You get what you pay for.
If home canning appeals to you, please allow me to point you toward the rec.food.preserving FAQ where much very good information about methods and techniques may be found.
One source of gallon sized glass jars are sandwich shops and restaurants that use pickled peppers. I have a Subway (tm) sandwich shop that saves its pepper jars for me and receive several per week.
Using dry ice to displace oxygen from food storage containers is a very straightforward affair. To prevent leaching plastic chemicals from the container into your food over a long period of time I recommend lining the bucket with a food grade plastic, mylar or brown paper bag before filling the bucket with your product. Be sure to wipe any accumulated frost off of the ice and wrap it in a paper towel or something similar so you don’t burn anything that comes into contact with it. Put the dry ice at the bottom and fill the container. Shake or vibrate it to get as much density in the packing as possible and to exclude as much air as you can. Put the lid on, but do not fully seal it. You want air to be able to escape.
Ideally, the dry ice should slowly evaporate and the cool CO2 should fill the bottom of the bucket, displacing the warmer, lighter atmosphere and pushing it out the top of the container. One pound of dry ice will produce 8.3 cubic feet of carbon dioxide gas so about four ounces per five gallon bucket is plenty. Do not move or shake the bucket while the dry ice is sublimating. You want to keep mixing and turbulence to a minimum. After about three hours go ahead and seal the lids, but check on them every fifteen minutes or so for an hour to be certain that you’re not getting a pressure build up. If you don’t have to let any gas off, then put them away. A little positive pressure inside the bucket is a good thing, but don’t allow it to bulge.
WARNING: Dry ice (frozen carbon dioxide) is extremely cold and can cause burns to the skin by merely touching it. Because of this you should wear gloves whenever handling it. Also, dry ice evaporates into carbon dioxide gas, which is why we want it. CO2 is not inherently dangerous, but you should make sure the area you are packing your storage containers in is adequately ventilated so the escaping gas will not build to a level dangerous enough to asphyxiate you.
IMPORTANT NOTE: Because dry ice is very cold, if there is much moisture in the air trapped in the container with it, and your food, it will condense. If there’s enough of it, it’s going to cause you problems. Try to pack your containers on a day when the relative humidity is low or in an area with low humidity, such as in an air-conditioned house. Use of a desiccant package when using dry ice to purge storage containers is a good idea.
Dry ice may be found at ice houses, welding supply shops, some ice cream stores, meat packers or you could look in your local phone book under the headings “dry ice” or “gasses”.
Both nitrogen (N2) and carbon dioxide (CO2) are commonly available in the form of compressed gas in cylinders. Of the two, nitrogen is the more inert and thus to be preferred. In food storage, CO2 is mainly used in the form of dry ice (see above) which is often easier to acquire with much less equipment needed to use it. Because of this, I’ll be limiting this section to the use of compressed nitrogen. If for some reason you prefer to use compressed CO2, the information given below will work for it as well, though cylinder sizes may differ.
In the U.S. there are about eight principal suppliers of compressed gasses: Air Liquide, Airco, Linde, Air Products, Matheson, Liquid Carbonic, MG Industries, and Scott. One or more of these producers should have compressed gasses available in virtually every area of the United States and Canada.
Locating a source of compressed nitrogen is probably as easy as looking in your local phone book under the headings “compressed gas suppliers”, “gasses”, or “welding supplies”. Other sources might be automotive supply houses, university or college research departments, vo-tech schools, and medical supply houses.
Nitrogen is generally available in a number of forms ranging from gas intended for welding, to various purity assured types, to gas mixtures where N2 would be one of the components.
Unless you are very knowledgeable about compressed gasses and the equipment needed to use them it is strongly recommended that you not use any gas mixtures in your food storage, but rather to stay with pure nitrogen gas. Use of compressed gas mixtures requires knowledge and equipment beyond the scope of this FAQ.
NOTE: Welding nitrogen is essentially a pure gas, but it has one important caveat. When a cylinder of welding gas is used there is an unknown possibility that some form of contaminant may have backfed into the cylinder from a previous user. Possibly this could happen if the tank was being used in an application where the cylinder’s internal pressure fell low enough for pressure from whatever the tank had been feeding to backflush into the cylinder. Alternatively, the tank pressure may have become depleted and was repressurized using ordinary compressed service air. The most likely contaminants will be moisture, carbon monoxide, carbon dioxide, oxygen and hydrocarbons, but there is the remote possibility of something even more exotic or toxic getting into your cylinder. Welding gas cylinders may not be checked by the gas supplier before being refilled and sent back out for use. It is this remote, but unknown possibility of contamination that causes me to recommend against the use of welding grade nitrogen in food storage.
The varying types of purity assured nitrogen gas are slightly more difficult to find and slightly more expensive in cost, but I believe this is more than made up for by the fact you know exactly what you’re getting. Air Liquide, as an example, offers seven types of purity assured nitrogen ranging from 99.995% to 99.9995% pure with none having a water vapor content over 1 part per million (ppm) or an oxygen content over 3 ppm. Any of them are eminently suited to the task so the most inexpensive form is all you need buy.
As you might expect, compressed gas cylinders come in a number of different sizes. For the sake of simplicity I will address only the most common cylinder sizes since they will almost certainly be the most inexpensive as well.
Again using Air Liquide as an example, it is their size 44 and 49 cylinders that are the most common. There are other cylinder sizes of smaller physical dimensions and capacities. However, the logistics of compressed gas production and transport being what they are, they frequently will cost as much or even more than the larger, more common sizes. The actual gas inside the cylinder is fairly cheap. Filling and moving the heavy cylinders around is not.
Obtaining the Gas and Necessary Equipment
Although you can purchase your own cylinder the most inexpensive way to use nitrogen is to rent a cylinder from your gas supplier. This may require filling out an application, paying a refundable cylinder deposit and buying the gas contained in the cylinder. Tank rental periods can vary, but the most common is for thirty days.
Having rented or purchased the cylinder you must now get it home. Delivery by the supplier can often be arranged or they may assist you in getting the cylinder into your vehicle. The preferred method of transportation is for the cylinder to be chained, clamped or otherwise solidly secured in a vertical position in the transporting vehicle with the cylinder cap in place. Transportation requirements vary from nation to nation, state to state and even city to city so your best bet is to inquire of your gas supplier to find a safe and legal means of moving the tank.
IMPORTANT NOTE: The major expense in using compressed gas is not the cost of obtaining the gas itself, but in the equipment needed to safely handle and control it. Unless you can borrow the appropriate mechanisms they will have to be purchased, new or used, and even the cheapest regulator and gauge is not inexpensive. There is a temptation to forgo the expense and not use a regulator, but I must caution strongly against this. As table 1 above shows, a full cylinder of compressed gas will have an internal pressure of 2000+ PSIG. Normal atmospheric pressure is about 15 PSIA. If the cylinder valve was opened only slightly too far a great deal of very high pressure gas will flow through the delivery hose and metal wand and the potential for serious injury when it began to whip around would be very great. For your safety, get the necessary equipment. If you purchase your own regulator/gauge cluster and/or your own cylinder, there is necessity for periodic maintenance. Regulators and gauges need to be calibrated (using a water deadweight calibrator) and cylinders need to be hydrostatically tested, typically every ten years for both. Your gas supplier can provide you with more detailed information.
The only equipment that will come with your cylinder is the cylinder cap. “Don’t leave home without it” and they mean it. All of the common cylinder sizes will use the CGA-580 (Compressed Gas Assembly) cylinder fitting. The downstream side of this fitting can be obtained with different threads, but a 1/4” NPT (National Pipe Thread) nipple is normally needed to mate with the regulator body. The nipple is really nothing more than just a short length of high pressure pipe. The CGA fittings come in a variety of metal compositions such as carbon steel, stainless steel and brass. The best choice is one which matches the composition of the regulator body. If the CGA fitting and regulator are to be used only with dry, non-oxygen gasses, in a dry environment then galvanic corrosion can be disregarded so the most inexpensive metal composition can be used even if it is not the same as the regulator. If it is to be used in a wet area, or with oxygen containing gasses then matching metal composition becomes very important.
When the tank is to be returned there *must* be some residual pressure still in the cylinder or the renter might have to pay a surcharge or lose their deposit. This is particularly true of purity assured gasses because the residual gas composition will be analyzed. This is done for the safety of all cylinder users.
The regulator/gauge cluster should be carefully removed using the same procedure that is described below to put it all together. Care should be taken not to damage the cylinder valve threads. Replace the cylinder cap and transport in the same manner as you brought it home.
Putting it all Together
If the fitting and regulator are bought separately then some 1/2” wide Teflon (tm) tape is recommended for assembly since it is a clean and inexpensive way of sealing pipe joints. Looking into the open end of nipple wrap the tape clockwise around the threaded end for 1.5 to 2 turns, working from the open end backwards. If you want to do a neat looking job, the tape may be slit lengthways to make it 1/4” wide, but this is not a requirement. A brass nipple may shrink somewhat during tightening and need a bit more tape than a harder metal like stainless steel would. The Teflon tape should only be used on the end of the nipple that attaches to the regulator body, NOT to any part of the cylinder end.
The regulator end has tapered threads and uses them directly for sealing. The cylinder end has straight threads and depends upon the precision mating of machined metal surfaces to seal. The cylinder end threads simply apply the clamping force.
Before attaching the CGA fitting to the cylinder the user should put on safety glasses and good hearing protection. The cylinder valve can then be cracked very slightly to blow out any dust or debris. After closing the valve, inspect the cylinder valve and nipple for any abrasions, nicks, gouges, embedded particles, etc., before attachment is made.
You will need two wrenches (not adjustable pliers) to equalize the torque, particularly on the cylinder valve where it should be minimized. Put one wrench on the fitting and the other wrench on the cylinder valve and make the join.
Once the regulator/gauge cluster has been mated to the cylinder, the delivery hose can now fitted to the regulator and the metal wand to the other end of the hose. The wand is nothing more than a short length of metal tubing at least six inches greater in length than the depth of the buckets to be filled. Copper water line works well.
When the joins have been made, a mixture of a short squirt of dish washing detergent and water can be used to check for leaks. Be certain the detergent does not contain ammonia. Pour some on each fitting working from the cylinder end outward, opening each valve and pressurizing as you go. Once the leak check is finished rinse off and wipe down all surfaces to minimize the chance of accidents in the future.
If the gas is not to be used at that time then the cylinder valve should be closed and all pressure should be drained to zero in the regulator and gauge. This should be done any time that the tank is not in actual use. If you have purchased your own cylinder then it is a good idea to also acquire one of the plastic valve plugs, similar to those seen with propane cylinders, in order to protect the cylinder valve threads and keep dust, debris and insects out of the valve.
WARNING: Care should be taken that the cylinder is used and stored in such a way as to minimize the risk of the tank falling over. With the regulator and gauge attached there is an increased likelihood of damage occurring to the cylinder valve should the tank fall. Catastrophic failure of the cylinder valve will turn the tank into a high-energy, unguided rocket with the capability of doing great damage and/or serious injury.
Having assembled and tested your gas system, you are now ready to begin the work of packaging your food. You’ll need containers, food grade plastic bags that are a bit larger in internal volume than the container, and some clean brown paper bags to fit inside the plastic bags. Next is the dry food you intend to package and a pack of matches or a cigarette. You’ll also need to wear the safety glasses and hearing protection you wore when you put the gas system together.
Take the containers you are going to use to store your food in, the bags that will line them and the food you are putting up and place them in some warm (not hot) area long enough for them all to equalize to that temperature. This will mean that the air contained inside them will also be at a warm temperature and make it more likely that it will stay on top when the cool gas from the nitrogen cylinder begins to flow in. The warm gas being on top will be the first to purge from the container, taking a good deal of the oxygen with it.
Line the interior of the container with a plastic bag and then line the plastic bag with a clean brown paper one. Fill the container with the food product shaking to get it as full as possible. Don’t forget to add your desiccant package if you’re going to use one. You don’t want any pockets left between the plastic bag and the container. Once you have gotten it full to just short of not being able to fully put on the lid, gather the top of the plastic bag together. Insert the wand to the bottom of the food, (take care not to tear the bags), and close the top of the plastic bag loosely around it. Now open the cylinder valve and set the regulator to a very slow gas flow and begin to fill the bags with gas. You want the container to fill slowly so you can minimize turbulence and mixing as much as you can. It’ll take a little while to fill each container, a few minutes per bucket. Just as with dry ice, the idea here is for the cool gas to displace the warmer atmosphere from the container. The bags should puff just a bit. When I think it’s full I’ll hold a lit match just above the bag in the air that is escaping from it. If it snuffs right out then I let it run for about a minute longer to flush out more of any remaining oxygen and remove the wand.
Tie the bag off and seal the bucket. Again, you want to have the bucket as full as possible so that there’ll be only minimal air space. You should monitor the containers for an hour or two after filling to check for any signs of bulging or other pressure build up as the cool gas inside gradually warms up and expands. A slight positive pressure is OK, but serious bulging needs some of the pressure released.
NOTE: Although the procedure for flushing a container with nitrogen is straightforward enough, actually getting a good purge of the container is not. Nitrogen flushing works best when the contents of the container are fairly coarse in size so that the gas flow around and through the food is free and unrestricted. Foods such as the larger sized grains (corn, wheat, barley, long grain rice, etc.), legumes and non-powdered dehydrated foods are best suited to this technique. Foods with small particle sizes such as flours, meals, and dry milks will flush with mediocre results.
Because of the difficulties in purging sufficient oxygen from a container to lengthen the shelf life of the food it contains many commercial suppliers have dropped this technique in favor of using oxygen absorbers. There is no reason that inert gas flushing and oxygen absorbers cannot be used together and one good reason that they should. If you are using five gallon plastic buckets as your storage containers, it has been observed that the absorbers can cause the air pressure inside the bucket to drop enough for the walls of some buckets to buckle, possibly leading to a seal breach or a stack collapsing. For this reason, flushing with inert gas (nitrogen or CO2) might be a good idea, in order to purge as much oxygen as possible so that the pressure drop caused by the absorber removing the remaining oxygen will not cause the bucket to buckle.
Oxygen Absorbers, Desiccants and Diatomaceous Earth
What is an Oxygen Absorber?
If all of this messing about with gasses sounds like too much trouble, you can try using oxygen absorption packets. I don’t know exactly when they first showed up on the market for use by private individuals, but they are a relatively recent tool for long term food storage. The packets,one brand is Ageless Z300E from the Mitsubishi corporation, absorb free oxygen from the air around them and chemically bind it. This removes it from being available for other purposes such as oxidative rancidity and respiration by insects or bacteria. The practical upshot of all this is that by removing the free oxygen from your storage containers, you can greatly extend the storage life of the foods in the containers.
Finding any information about these absorbers has been difficult, but, thanks to Al Durtschi, I was able to find a study of their effectiveness from Brigham Young University.
The study tested the absorption capacity of the Ageless Z300E packets. It found they were even more effective than their rated absorption capacity of 300 milliliters of oxygen (O2 at sea level pressure). A single packet sealed into an empty #10 can (80% of one gallon) reduced the oxygen in the canned air to less than 1/2%.
The following is the verbatim text of the conclusions section of the Brigham Young study. See V.B Pamphlets for the complete citation of this study.
Conclusions: “Oxygen absorbing packets are effective in reducing oxygen contents in sealed cans. The ageless Z300 packet has a greater than claimed capacity for absorbing oxygen. Packets abused by 4 hour-exposure- to-air still exceed claimed capacity. It may be economical to use smaller packets based on the dead air volume instead of can volume. Smaller packets would have less tolerance for abuse and personnel would need to be more diligent in protecting the packets.”
“The level of oxygen remaining in the presence of the absorber packets is sufficiently low to greatly retard development of rancidity. The biological consequences are not so easy to predict. Microorganisms range from aerobic to anaerobic, thus no unqualified statement can be made. The energy requirements of anaerobic bacteria are met by reactions between oxygen and more than one other molecule. This makes bacterial energy a higher order of reaction than rancidity. Thus, the rate of bacterial aerobic reaction would be more seriously retarded than rancidity. These matters are not of practical importance because the products to be canned should be too dry to support microbial growth. Insects are aerobic and would like-wise suffer retardation of activity. No comprehensive statement can be made about irreversible inactivation or death of insects. As long as the oxygen level remains low, insect activity will be lower by at least the square root of oxygen content. In a practical sense, these packets are effective in stopping insect activity. USDA does not recognize any method except disintegration as effective for completely killing insect eggs.”
Where Can I Find Oxygen Absorbers?
Because they are a relatively new tool on the food preservation and storage market, oxygen absorbers have not yet achieved a widespred dissemenation amongst the various storage food dealers and suppliers. They are available, but you may have to do a bit of searching to find them.
In addition to the above suppliers it may be possible to acquire oxygen absorbers through a LDS family cannery if you have one locally available. Please see the section on these canneries for information on how to explore this possibility.
How Are Oxygen Absorbers Used?
Even though they apparently will absorb a great deal more than the 300 ml of O2 they are rated for, the following instructions for use are based on their listed rating. So, when using the Mistubishi Ageless Z300E oxygen absorption packets, you should allow one packet for every quart and a half (1430 ml) of remaining air volume in your filled storage containers.
Now determining the volume of air remaining in a filled container is no easy thing. In the study, #10 cans filled with either elbow macaroni or powdered milk were used and their respective air volumes were determined. A can full of elbow macaroni was found to contain 22% remaining air volume and a can full of powdered milk was found to contain 10.5%. With these as guides, you should then be able to roughly figure the remaining air volume of the foods you have in your containers. You’ll have to decide whether the food you are working is closer to the macaroni or the dry milk in its packing density. Obviously, this is a rather rough rule of thumb and this is why I kept my instructions to the listed ratings rather than on what they will apparently really do. The excess capacity will thus serve to cover the shortcomings of your reckonings. These absorption packets should be used only in dry foodstuffs and not with any product that will get them wet.
NOTE: If you do choose to use oxygen absorbers in packing your food storage containers you should give some consideration to the container you’re using. The absorber is going be removing the 20% of the atmosphere that oxygen constitutes. Since nothing is replacing it this will leave the interior of the storage container with a lower atmospheric pressure than the outside. If the container is sufficiently sturdy this pressure differential will be of little consequence. For containers with thinner walls or more flexible material the pressure drop could cause them partially collapse or buckle, particularly if other containers are stacked upon them. This could make them more likely to lose seal integrity. The sturdier plastic buckets (Superpails, etc), or metal cans should have no problems. Other containers should probably be tested or first flushed with an inert gas (N2, CO2) before the absorber is sealed in.
If anyone out there knows of more precise instructions for the use of these O2 absorbers, particularly if they’re from the manufacturer, I’d appreciate it if you’ll send them to me. To date, the study that Al pointed out to me is the only solid data I’ve found. It is from it that I derived the instructions I have given above.
What is a desiccant?
A desiccant is a substance with very hygroscopic (adsorbs moisture from the air) properties. There’s any number of different substances that meet this description, but only some of them will serve our purposes.
The most commonly used desiccant is silica gel. This is an amorphous, highly adsorbent form of silica. It is most easily found in a form called “indicating silica gel” which are small white crystals looking much like granulated sugar with small colored specks scattered throughout.
Those specks are how we determine whether the gel is dry or has adsorbed all of the moisture it will hold. If the specks are blue, the gel is dry and capable of carrying out its moisture adsorbing mission. If the specks have turned pink, then the gel has adsorbed all it will and is now saturated. Part of what makes silica gel so useful is that it can be refreshed by driving out the adsorbed moisture so it can be used again. This is a simple as pouring the saturated desiccant into shallow pans and placing in a 250 F oven for no more than five hours until the colored crystals have once again turned blue. You can also do the same thing in a microwave. Stir thoroughly and repeat until dry.
Although I’ve never found anything that mentions this, apparently it is possible for silica gel to break down over time, or at least the colored crystals can. I had a five pound can stored in an outside shed here in Florida for several years before I opened it again to use some of it. Nearly all of the colored indicator specks had broken down and disappeared. I don’t know if the gel itself was still good and with no way to reliably determine whether it was saturated or not, I discarded it. The can the gel was in was just cardboard and it gets very humid here in Florida so it really was very poorly stored. Under decent conditions it may not break down at all. (I’ve never heard of this occurring, anyway.)
There are other desiccants, but I am not familiar with any that can be used with foodstuffs. I know that Kearny recommends using a piece of gypsum wallboard as a desiccant in his expedient radiation meter in Nuclear War Survival Skills, does anyone know if this can be used with dry foodstuffs? How about other desiccants?
From: Pyotr Filipivich; Simple trick is to dry a piece of wood in the oven - and once it is bone dry (more than usual) then put it in your container and seal it. The wood will suck up any available moisture.
Where do I Find Dessiccants?
I buy all of my silica gel at Wal Mart in their dry flower section where it is sold in one and five pound cans for flower drying. I’ve seen it sold the same way in crafts stores and other department type stores that carry flower-arranging supplies. You can also buy it from many other businesses already prepackaged in one form or another to be used as an absorbent. All of the desiccant that I’ve found packaged this way has been rather expensive (to me) so shop carefully.
How do I Use Desiccants?
The key to storing many foodstuff for the long term is dry, dry, dry. Available oxygen and storage temperature also play roles, but it is moisture content that determines whether you get usable food out in five years or not.
Therefore, the idea here is to have the food you want to put into storage as dry as possible before it goes in and then take steps to deal with any moisture trapped, generated or leaked into your storage containers.
Ideally, the foodstuffs you have on hand will be no more than 10% moisture. If this is the case then you can go ahead and seal them into your storage containers using the packaging method of your choice and have a reasonable expectation of your food staying in good condition.
If your storage foods aren’t sufficiently low in moisture content then you’ll need to reduce the water they contain. Wheat has been found intact in Egyptian pyramids where it had lain for several thousand years. It was the bone dry desert air and the cool interior temperature of the pyramids which kept it from rotting away. We can approximate that Egyptian climate by several methods.
The least involved method is to wait until the driest time of year for your location. If this doesn’t suit, then turn your air conditioning on a little high. Bring in your buckets, lids, and the storage food. Let everything sit in a well-ventilated place where it’s going to get plenty of cool from the a/c. I’d avoid anywhere near the kitchen or bathroom areas, as they put out a lot of moisture. Stir the food frequently to maximize moisture loss. About three days of cool, constant air flow and low humidity ought to dry things out a bit. Due to its highly odor absorptive nature, I would not do this with any dried milk products or other powdered foods, flours or meals . This method works best with coarse particles such as grain, legumes and dried foods.
If this won’t do, you can place a large quantity of desiccant in your storage containers. Fill the remaining space with your food product and seal on the lid. After about a week, unseal and check the desiccant. If it’s saturated, change it out with dry desiccant and reseal. Continue to do this until the contents are sufficiently dry. If it doesn’t become saturated the first time, change it anyway before sealing the bucket permanently. You’d hate to find later it saturated in storage.
I use silica gel for practically everything. My usual procedure is to save or scrounge clear plastic pill bottles such as 500ct aspirin bottles. Fill the bottle with the desiccant (remember to dry the gel first) and then use a double thickness of coffee filter paper carefully and securely tied around the neck of the bottle to keep any of it from leaking out. The paper is very permeable to moisture so the gel can do its adsorbing, but it’s tight enough not to let the crystals out. This way whatever moisture does inadvertently get trapped inside can be safely absorbed. It won’t dry out a lot of moisture -- you still need to take steps to get everything as dry as possible before you pack it -- but it will take care of what little is left.
IMPORTANT NOTE: The indicating form of silica gel (has small blue specks in it) is not edible so you want to use care when putting together your desiccant package to insure that is does not spill into your food.
I’ve never found any certain rule of how much silica gel to use to how much dry goods. For my purposes, I use about four ounces of gel to a five gallon bucket of dry grain and beans. If I think the moisture content is over 10% when I seal them, I’ll go as high as a half pound. This might be ridiculous overkill, but in Florida everything is high in moisture because of our ever present humidity. For a one-liter bottle of dry milk I’ll use about one ounce of silica gel rolled up in a paper cartridge made from a coffee filter. If you’re familiar with them, it looks like a paper cartridge such as you’d use for black powder weapons. They fit nicely into the bottle and keep the gel in.
What is Diatomaceous Earth?
Diatomaceous earth is a naturally occurring substance comprised of the fossilized remains of marine diatoms. These diatoms are microscopic in size and are covered in sharp spines that make them dangerous to exoskeletal insects, but not to animals with internal skeletons. The spines of the diatom skeletons pierce the soft body tissues of insects between their hard exoskeletal plates and it is through these numerous microscopic wounds that the insect loses bodily moisture to the point of dessicating and dying. Creatures with internal skeletons such as humans, cattle and pets have means of resisting such damage and are not harmed. Thus, it is possible to mix a small amount of DE into your stored grains and beans to control insects without having to remove the dust again before you consume them.