Rotate cached food by replacing each cache before its food reaches its maximum age, stagger the caches so that only one is open at a time, and weigh every container on each visit, because a gain in weight is the earliest sign of water getting in. Every opening exposes the cache to being seen, so check the surface often and open the container rarely, and treat any bulging container as lethal.
Part of Hidden Food Caches
Cache inventory and rotation is the scheduled opening, weighing, consuming and replacement of cached food so that the stock stays within its shelf life without the visits giving the caches away.
Visiting A Cache Is Both The Cure And The Risk
The parent article says to check every cache every 3-6 months by opening the container and inspecting for moisture, pest damage and container degradation; to rotate food by eating the oldest and replacing it, which keeps the stock within its shelf life; to update the inventory list at each access; and to vary your route so that no path wears. Emergency Caches gives maximum intervals before rotation: 5 years for white rice and hard wheat in hermetic containers, 2-3 years for dried beans and lentils, no rotation for salt and honey beyond an annual spot check of seals, 2-4 years for hard tack, 1-2 years for dried meat and 3-5 years for canned goods by their dates.
The two sources disagree about how often to open a cache, and both have a point. Opening a container admits air and moisture and, more importantly, puts a person at the site, while never opening it leaves a leak undiscovered. This article does not settle the disagreement by preference. It puts numbers on each side so that the trade can be made. No external source supplies the figures below; they are arithmetic on the corpus’s own numbers and on stated assumptions, and the assumptions are the part to replace with your own measurements.
What You Need
- A record kept inside each container — date packed, contents, gross weight; see Inventory Management
- A scale you can carry, accurate enough to see a difference of a hundred grams or so
- A rotation plan that assigns one cache to each season
- A way to replace what you open — fresh liner, desiccant, wax, food
Method: Surface Checks Often, Openings Seldom, Weigh Every Time
Step 1: Record the gross weight when you seal. Container, liner, desiccant and food together, written on the list inside.
Step 2: Check the surface without digging. A short look from a distance at the ground above a buried cache or the cover over a hidden one shows disturbance by animals or people. This is the frequent visit and it should take minutes.
Step 3: Open on a schedule that depends on the food and on how the cache is built, from the maximum intervals above. Stagger the openings so that no two caches are open in the same season.
Step 4: Weigh the container. Compare with the sealed weight on the list. A gain beyond the scale’s error means water has come in; a loss means pests or spillage. See the worked example.
Step 5: Inspect the food. Look, smell, and check for mould, caking and insects. If a container is bulging, hisses on opening or smells foul, close it and see the danger note.
Step 6: Build the replacement before you open the old one, so there is never a gap in cover. Bury the new cache first, then dig up the old one.
Step 7: Eat the old stock in the household’s normal meals, at the daily rate; do not carry it away to be stored elsewhere.
Worked Example: Rotation Load And Exposure For A Household Of Four
A household of 4 eats rice at 0.55 kg per person per day (from the inventory article): 4 × 0.55 = 2.2 kg a day. Its three caches, sized as in Cache Network Planning, hold 30.8 kg, 6.6 kg and 30.8 kg of rice, 68.2 kg in all.
Rotation load. At a 5-year maximum for hermetic rice, each cache is replaced once in 5 years, so the household eats 68.2 ÷ 5 = 13.6 kg a year of old stock, which is 13.6 ÷ 2.2 = 6.2 days of its rice supply. The food cost of rotating is small. The main cost is the work and, above all, the visits.
Exposure. Suppose, as an assumption, that each opening has a 2% chance of being noticed by someone. The chance of at least one noticed opening in a year of k openings is 1 − 0.98^k.
- Opening all three caches every 3 months is k = 12 openings a year: 1 − 0.98^12 = 1 − 0.785 = 0.215, or 21.5%.
- Every 6 months is k = 6: 1 − 0.98^6 = 1 − 0.886 = 0.114, or 11.4%.
- Every 12 months is k = 3: 1 − 0.98^3 = 1 − 0.941 = 0.059, or 5.9%.
Detection lag. If a seal fails at an unpredictable moment, a check every T months leaves it undiscovered for T ÷ 2 months on average: 1.5 months at T = 3, 3 months at T = 6, 6 months at T = 12. How bad that is depends on how fast the damage runs, and the time for mould or pests to ruin dry rice is not given by any source I can cite.
Water gain. One percentage point of moisture in 15 kg of rice is 15 × 0.01 = 0.15 kg, or 150 g of water (see Cache Moisture Control). A container that weighs 400 g more than at sealing has gained about 400 ÷ 15,000 = 2.7 percentage points, enough to need attention, since the grain article sets the safe moisture limits only a point or two apart. A scale that reads to 100 g catches this; one that reads to a kilogram does not.
What follows. Frequent surface checks cost almost no exposure, and the weight check makes an opening informative. Open less often than the parent article’s 3-6 months where weighing and surface checks show nothing, and more often where they do. The figure of 2% is mine; measure how often you are really seen, and replace it.
Common Mistakes
- Opening every cache in one trip. You are away from home for a long time, at several sites, with a pattern.
- No weight on the list. Without it the weighing tells nothing.
- Eating the oldest food without checking it. The oldest stock is the likeliest to have failed.
- Updating the list at home from memory. Write it in the cache while you have the container open.
- Rotating all caches in the same month. One bad season takes them all.
Safety
A swollen container is lethal; a visit you can't hide is a hazard
Never taste or cook food from a bulging, hissing, leaking or foul-smelling container; botulinum toxin does not need to smell and is not destroyed by the warmth a cache gets. Dispose of it sealed, away from animals and people, and wash hands and tools afterward; see Food Safety. If you suspect that you are being watched, abort the visit and return another day, as the parent article advises. A compromised cache is worse than none, since it draws attention to your supply network. Do not lift a full container alone with a bad back: it weighs about 15 kg for a rice bucket.
What’s Next
- Learn next: Retrieval Under Pressure — when the visit is not on schedule
- Combine with: Grain Storage — the moisture limits behind the weight check