There is nothing that creates a link with the past quite like an item you can hold in your hands, knowing that the last time somebody held it was a hundred (or more) years ago. Time capsules are a good way to make that link, if they are created with care.
Here are some things to keep in mind when creating a time capsule that will last for a century or more:
Choose the retrieval date - when will it be opened?
The longer the capsule is to be sealed, the more difficult the choice of items to go into it. Also, more factors must be taken into consideration when choosing the location of the capsule and the material from which it is made.
Location - where will the time capsule go?
It is not recommended that time capsules be buried; many have been lost due to their location being forgotten, changes in geography, or urban renewal. If the time capsule is buried, it is important that the location be marked with a plaque describing the mission of the time capsule. Also, burial will effect the container and increase the chance of leakage. The best burial method is to first build an underground vault using concrete or bricks, making sure that it will drain well. Line the vault with fiberglass insulation.
If you want a specific retrieval date for the time capsule, do not place it in a corner stone of a building. Time capsules in corner stones are only retrieved at the destruction or major overhaul of buildings.
Above ground storage of time capsules is the best option, especially for time capsules with a specific retrieval date. Time capsules can be stored in buildings, in plain sight; they dont have to be hidden away.
Types of Containers
Time capsules should be sealed completely to keep out air and water, which can effect the contents of the capsule. Capsules should be seamless or very well welded. Soft soldering (such as lead) can deteriorate over time, allowing moisture to enter.
Stainless steel Best
- Welded shut not expensive to close but could prove difficult to open in 100 years. Will be very good at withstanding water damage, etc. However, heat from the welding can damage contents.
- Wing nut clamps more expensive than welding; will need an O-ring seal, which might decompose over time, allowing moisture to enter. Threads of the wing nuts may seize over time and will be difficult to open.
- Threaded cap more expensive to make, and will need an O-ring seal, and its threads may seize. (See above).
Aluminum also an excellent choice
- Same features as stainless steel.
Polypropylene - good for above ground
- Seamless construction.
- Chemical make up may break down under ground, allowing moisture to enter.
- Lids can be sealed shut using heat or epoxies.
Polyethylene - good for above ground
- Might become permeable to moisture as it ages, so must be encased in a waterproof enclosure if it is to be buried.
Polyvinyl chloride (PVC) - NOT recommended
- Its chemical components are known to be unstable, and will break down in a process that cannot be reversed.
- Will also release harmful acids into the interior of the container.
Glass - good for storing items inside the capsule
- Seamless construction
- Easily broken
- Lids may not retain a seal over long periods of time.
Select the items for your capsule
Your time capsule will be unique to your group or family, and the items chosen should reflect this. There are other institutions, such as archives and museums, saving things, too but they will not have the things that will be most important to your group. Choose the things that best represent what you want future generations to know about you, not just what you think an archives might keep.
Keep in mind the number of years that will go by from when you seal your time capsule to when someone opens it up. If technological change occurs as rapidly in the next 100 years as it has in the last 100 years, the people of the future might not know what a video tape, an optical disc, or a play-station game is or have the the equipment to play it on. If you wish to include articles that need playback equipment, include the equipment, along with detailed instructions on how to use it and type of energy needed to run it (voltage and current requirements). Include the software as well as the hardware if needed.
The longest lasting items:
- Black and white photographs treated with gold, selenium or polysulfide toner on a fiber base
- Photograph slides printed on a polyester base will last longer than those printed on an acetate base.
- Some textiles cotton and polyester are the most stable
- Acid free, permanent paper (preferably cotton) of a pH of 7.0 to 8.5
- Pencil or archival quality inks
- Microfilm or microfiche produced to archival standards on a polyester base will last 100 years and will be viewable with only sunlight and a magnifying glass, should future technology lack micrographics
- Wood will last, but must be sealed away from electronics due to gasses released during decomposition
- Glass breakable, but enduring.
- Pottery and ceramics like glass, it is breakable but enduring
- Freeze-dried foods well sealed!
- Nonferrous metals copper, brass, gold, stainless steel, also well sealed
Items that will not last:
- Color photographs
- Photographic slides on an acetate base
- Other textiles silk can deteriorate in oxygen, wool and hair contain sulfur and will corrode metals, nylon decomposes
- Batteries deteriorate and release harmful chemicals while doing so. Do not include batteries in any electronic equipment
- Diazo microfilm releases ammonia as it decays
- Polyvinyl chloride and polyvinyl acetate will decay even in sealed capsules
- Rubber releases sulfur
- Video, audio, and computer tapes life expectancy of modern magnetic tapes can be as short as 10 years due to the breakdown of the binder that holds the magnetic particles onto the tape
- Pressure sensitive adhesive e.g. magic or masking tape
- Canned food can explode
- Live ammunition
Create a detailed listing of the items placed into the time capsule. Include the materials from which they are made and their functions. Include one copy of this in the time capsule and retain one copy for your records. Use archival paper and inks or pencil for this!
Preservation of the items
Items will endure their stay in the time capsule if they are protected and insulated to some extent from each other. Each item should be housed individually in the type of enclosure best suited to its needs. Some will need to be sealed inside their containers, and some will not.
- Photographs and slides acid free envelopes or sleeves
- Textiles be sure they are clean and dry, then wrap in acid free tissue
- Paper or books inside acid free folders, boxes, or in Mylar (polyester) sleeves
- Microfilm or microfiche acid free cardboard boxes
- Glass, pottery and ceramics pad well
- Wood seal inside glass, away from any electronics; be sure to pad the glass
- Freeze dried food sealed and then sealed in glass containers. Pad well
- Electronic equipment and media inside anticorrosion enclosures, and sealed in glass; pad well
- Metals inside anticorrosion enclosures, and sealed in glass; pad well
Labeling items is good, but do not use adhesive backed labels or attach them with tape. The adhesive will dry, and the labels will fall off. Include the label (on acid free paper, written in pencil or archival ink) with the item inside the packaging.
Packing the container
Keep all the items, labels, packing materials, and the time capsule in the same well air-conditioned environment for several days. This allows the materials to dry and reach the same temperatures prior to packing.
Place the heaviest items at the bottom.
Fill empty spaces with crumpled, acid free paper to prevent shifting (you could have fun photocopying newspaper articles onto the paper first and use it as packing material).
Any absorbent materials (textiles, etc.) will need to be dry before placing in the capsule. Keeping them in a well air-conditioned environment for several days prior to packing will help.
Silica gel or other desiccant materials may be placed in the container to help absorb excess moisture for the duration. Acid free blotting paper (well dried in an oven) is another option. Be sure to cool the blotting paper to room temperature before placing it in the container, but do not allow it sit too long, as it will absorb moisture from the air.
Sealing the container
Some time capsule companies offer the additional services of removing the oxygen from the time capsules that they sell and replacing it with nitrogen or argon gas. This can very much increase the chances of the contents lasting for 100 years or more.
Depending on the material used for the capsule, it might be a good idea to create a box within a box by placing the time capsule inside another container. Fill the space between the time capsule and the outer box with wax (NOT bees wax) to act as a barrier from moisture.
First, have a ceremony to place the capsule. Invite the media, take lots of pictures, and engrave a plaque and put it into place.
Next, remember the capsule by having annual ceremonies, picnics or reunions.
And not least, list the capsule with the International Time Capsule Society (http://www.oglethorpe.edu/itcs/ )
Professor Paul Hudson
Dr. Brian Durrans