Creating a time capsule

Time capsules are created to commemorate an event or to capture a moment for the future. Some time capsules are buried, some are located in specially-designed building cavities and some are placed in vaults or safety deposit boxes. In recent times commercial providers have developed family capsules intended to be placed prominently in the home to be opened on a particular date.

Careful choice of materials to be included in a time capsule will contribute to the longevity of both contents and capsule.

Planning the project

Before constructing a time capsule or deciding what to put in it, set aside some time to plan the project. This will deliver a better result in the long term – which is precisely the point of a time capsule. Four questions should be asked as part of the process:

  • Who is your proposed audience?
  • What do you want to say?
  • Where will the capsule be placed when closed?
  • When will the capsule be opened?

Considering these questions will make it easier to choose items that meet the aims of the project as well as items that are most likely to survive intact until the capsule is recovered in the future.

What to include in the capsule

Items most suitable to include in a time capsule are those that are not likely to be affected by changes in technology, or to require special equipment to be read or used.

Where possible all items should be made of inert durable materials, able to withstand the specific conditions of storage planned for the capsule. If this is uncertain, plan to isolate individual contents within the capsule by packaging materials separately. This will create micro-environments able to provide the best possible protection for a diverse range of materials. Good packaging can also prevent contact between any potentially non-compatible materials in a capsule.

  • Use archival quality paper for all documents.
  • Avoid use of water-soluble inks, felt tip pens, and bubble jet printers in creating documents.
  • Newspapers are generally printed on poor quality paper, and are not suitable for long-term inclusion. Photocopy originals onto archival paper and place these copies into the capsule.
  • Use black-and-white prints rather than colour, if choosing to include photographs. Make sure the prints are hand-processed rather than machine-processed. Hand processing generally results in more thorough washing of prints, which contributes to their greater durability.
  • If you want to use colour, use colour transparencies (slides) – they are more durable than colour prints.
  • Avoid placing video recordings in time capsules. Their stability is not guaranteed beyond 20 years at best, and they are dependent on appropriate playing machinery being available when the capsule is opened.
  • Avoid audio cassettes as they present similar problems to video recordings. If a recording must be included, use studio quality reel-to-reel tapes. The durability of these, however, will depend on a stable environment within the capsule.
  • Avoid CDs if the capsule is to be sealed for more than 10 years. Although CDs are quite stable, the technology supporting them is changing so rapidly that it is likely that playing equipment will have been superseded when time comes to replay the CD.
  • In general, avoid items that require equipment to play or view them. Anything in this category should be included only to provide examples of existing technology. Don't assume that suitable playing equipment will still be available when the capsule is opened.
  • Avoid rubber items, as rubber will deteriorate over time, releasing sulphur gas into the capsule.
  • Use only textile items that are clean and insect-free. Wool and hair may give off sulphur gas over time, so if these are used package the items containing this material separately and isolate them from other items in the capsule.
  • Use stable packaging, ie polypropylene, polyethylene or archival paper, to separate items in the capsule made from different materials.

Container options

Any container used as a time capsule should be strong, waterproof and materially stable. It must be capable of being tightly sealed to exclude both air and moisture. Choice of container will depend on how long it is planned for the time capsule to remain sealed and under what conditions. Where long-term burial, ie greater than 10 years, is planned, more sophisticated/expensive construction and materials are required.

  • For long-term burial, suitable capsule materials include copper alloy or high alloy stainless steel. Ideally, the container should be fabricated without seams, or if this is not possible it should be of welded construction, sealed with a screw top and gasket, or welded shut. Avoid the use of soft solder, as this will deteriorate faster than the rest of the capsule.
  • For shorter term burial, suitable capsule materials include high-density polyethylene tubing, pyrex glass, or brass.
  • Avoid capsule materials that contain iron (other than stainless steel or galvanised metals).
  • A secondary container is a practical way of buffering both capsule and its contents from moisture and environmental changes, and it can also allow for less stringent standards in the make-up of the capsule.

Packing the capsule

Planned preparation of the items for inclusion in the capsule will contribute to their longevity, but it must be acknowledged that the contents will be subject to inherent deterioration regardless of their initial condition.

  • Use new, good quality items in best possible condition.
  • Use gloves when handling and packaging items, and when placing them in the capsule.
  • Do not use glue or metal fasteners such as paper clips or staples to group items together.
  • Avoid folding or bending items to make them fit into the capsule. If necessary roll larger items around a core to reduce their size.
  • Don't overcrowd the capsule by including too many items. Items should be easily removable without damage.
  • Label items in the capsule using archival paper or card and permanent ink. Attach labels to items using linen cord, polyester or nylon cord such as fishing line.
  • Include a list of items contained in the capsule, and any instructions that might be necessary.

Choosing a site

The ideal location for a capsule is one that will provide stable levels of temperature and relative humidity. If such a location is not available, then the following points should be considered:

  • If the item is to be buried, place in well-drained soil with no ground water.
  • Avoid areas known to contain water mains, sewers, gas pipes and electrical cabling.
  • Choose a site that can be expected to remain undisturbed, but mark it so that it will not be overlooked or forgotten in the future.

As part of ensuring the success of a time capsule project arrange for succession planning, so that those who 'inherit' the capsule are aware of its existence. If the time capsule is a community project, lodge details at the local library, council archives or local historical society. It would be useful to include instructions on how to open the capsule with these details. Finally, be sure to establish some means of dealing with unforeseen contingencies that might occur between the capsule being sealed and its due opening date.

Copyright National Archives of Australia 2019