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Subject: Time capsules

Time capsules

From: Jack C. Thompson <76520.3531>
Date: Monday, October 19, 1992
The church is in a fairly dry part of the country, and, although
sandstone wicks moisture well, the fact that nothing much happened
inside the cavity during the past hundred years, it bodes well for the
next hundred. Soldered copper sheet boxes were pretty common, and the
damage you described is not uncommon.  Should the same sort of box be
planned for the next internment, you might consider suggesting that they
seal or coat the time capsule with melted beeswax.  If space permits,
and finances are nil, and you are down to the last hour (and that's what
it sounds like), you might consider what I once did in a similar
situation.  Take a 5 gal. pressurized soda pop container (make that,
accept the gift of...), de-pressurize it and clean it thoroughly.  Remove
the neoprene seal at the opening.  Then build a mylar dam around the
upended cap and pour in beeswax until it is level with the plane of the
cap.  Insert the material to be preserved into the container (most
material will have to be rolled/curled to get inside; a book would
likely have to be disbound, etc.).  Set the cap in place and secure it
with the wire bale.  There are two fittings on these containers: one to
pressurize the container, and the other to remove the syrup/pop.  Set
them in the normal upright position (set it, actually; I was thinking
about filling the containers I have with homebrewed ale) and hook up the
charging /discharging hoses and begin charging the containers with co2
whilst bleeding off the outgassing.  Co2 is heavier that oxygen and will
displace it in the container.  How to tell when the job is done?
Pressurize the container for 5 seconds, while bleeding off at the
discharge side.  Too much of this and you will have condensation (dry
ice, melting) inside the container, and then shut off the outflow.  Let
things settle down (i.e. warm up for a bit) and then bleed off the
pressure and recharge.  Do this a couple of times, keeping an eye on the
beeswax seal, which we'll get back to.  If the seal blows out, run a hot
air gun around the seal (once things settle down settle down) to re-seal
the lid, and continue at reduced pressure.  You're not trying to pump
pop, just a gas. There will still be some oxygen left in the container,
but not much.  Now, put mylar around the top of the container and pour
in melted beeswax to cover the cap, the top of the container, and the
gas fittings (hoses removed at this point).  It's not as elegant as some
time capsules I've been involved with, but it is a double walled
pressure vessel made from stainless steel, and beeswax has one of the
best track records around.

Jack Thompson
Thompson Conservation Laboratory Portland, Oregon

                  Conservation DistList Instance 6:24
                Distributed: Thursday, October 22, 1992
                        Message Id: cdl-6-24-002
Received on Monday, 19 October, 1992

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