We (my daughter and I) are building some time capsules in a bottle, i.e., putting photos, letters, small memories and so inside some glass bottles.

We plan to have a good lifespan of some: 10 years, 25 years and 50 years. They will be buried about 3 foot deep in places that won't have any load, so we're confident that they will not break.

But I'm afraid about humidity and mold. Using common tools and materials, how can I prevent mold from building in? And how can I seal the bottle, so that there is no humidity to damage our paper?

  • If your seal is at all competent, you won't have moisture ingress from the environment since it can't get past the seal. The only moisture will be what you put in there when you seal it. May 17, 2018 at 20:33

1 Answer 1


It's really hard to assure that they won't be under load anytime in the next 50 years. Obviously, the bottles only need to break once to be ruined. Also, depending on the type of bottle, it might be hard to find lids that are waterproof, rustproof, and won't decompose.

I recommend using something sturdier, like large diameter PVC or ABS pipe. It's easy to work with, you can cut it to whatever length you want, and it's easy to completely seal it off from the outside world.

You'll inevitably have at least some humidity from the air trapped inside, so I recommend adding some desiccant packets to help preserve the contents.

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