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A while ago i posted about a chest i buried for my son, to be found when he turns 10. Worried about the condition, i decided to dig it up after 4 years. This is how it came out. Reddit, i need tips on how to do it right this time.(r/WhatsInThisThing)
There are plenty of choices. Ammo cans are a great option, but after years of Geocaching, I’ve even seen those fail sometimes. My suggestion, if you want to bury it and keep the moisture from damaging the contents would be different chambers. Basically put a box in a bigger box. If you want to keep it small, get an ammo can and a Lock & Lock or Pelican case that will fit inside the ammo can. Put your treasure into the small box and stick that into the ammo can. For best assurance, I’d actually suspend the smaller box inside the ammo can with some expanding foam. If you want to go bigger, suspend the ammo can in a 5 gallon bucket with a lid secured on it (also with foam).
A common mistake that people make in Geocaching is to put the contents of the cache (specifically the log book) inside a cheap plastic bag. After moisture gets to the log, and inside the bag, it takes forever for it to leave. If you put a smaller box inside a larger box with foam all around, moisture will not be able to get to the treasure inside.