Select a Container
Time capsules should be sealed completely to keep out air and water, which can damage the contents.
Capsules should be seamless or very well welded.
Soft soldering (such as lead) can deteriorate over time, allowing moisture to enter. Here are some options and considerations for choosing a time capsule container.
Stainless steel is the best choice
Options and considerations for sealing these are:
- Welded shut – these models are not expensive to close but could prove difficult to open in 100 years. Will be very good at withstanding water damage. However, heat from the welding can damage contents.
- Wing nut clamps – more expensive than welding; requires an O-ring seal which might decompose over time, allowing moisture to enter. Threads of the wing nuts may seize over time, making it difficult to open.
- Threaded cap – more expensive to make and requires an O-ring seal, and its threads may seize (see above).
Aluminum
Also an excellent choice; same considerations as stainless steel.
Polypropylene
Good for above ground.
- Seamless construction.
- Lids can be sealed shut using heat or epoxy.
- Chemical makeup may break down under ground, allowing moisture to enter.
Polyethylene
Good for above ground.
Might become permeable to moisture as it ages, so must be encased in a waterproof enclosure if you are going to bury it.
Polyvinyl chloride (PVC) is not recommended
- Chemical components are unstable and will break down irreversibly.
- Will release harmful acids into the interior of the container.
Glass
Good for storing items inside the capsule if well packaged.
- Seamless construction.
- Easily broken.
- Lids may not retain a seal over long periods of time.
