Water pipes in archival storage

Jerry Shiner <jshiner [at] microclimate__ca> writes

>Liz Bowerman discussed using vacuum encapsulation of books and
>documents as a method of protecting them from accidental water
>damage. She also mentioned some other advantages (compaction,
>security, and protection from damage from external pollutants), as
>well as touching on the dangers (trapped off-gassing from the
>documents). Another problem can be off-setting of some printing when
>photocopied documents are stored under high vacuum.

I am intrigued by this problem of off-setting of inks from vacuum
packed photocopied documents. I have been selling the ArchiPress
system since 1992 and have never seen this happen. Perhaps another
kind of bag might affect the contents differently?  Jerry does not
say if the ink off-sets to the plastic of the bag or to other paper
within the bag? Has any DistList reader come across this phenomenon
within a vacuum bag?

An advantage of vacuum packing is that it is rigid and self
supporting and it is easy to see if a bag has been punctured because
it will deflate and can be replaced with a new bag. This means for
regular document storage you do not need to have any other form of
monitor to tell you if a low oxygen environment is being maintained.
Until recently monitoring has been difficult because it has been a
question of taking samples from within the bag using a probe or
using an Ageless eye tablet which are know to be unstable and have a
limited lifespan. Only recently with the introduction of the GSS 450
Gas-Fill Analyser are we able to offer a practical and effective
measurement system for anoxic environments. With this system a small
sensor can be sealed in a bag and monitored by an optical scanner
from the outside to give a reading of the level of oxygen within the
bag.

I also sell the RP system with PTS bags and Escal barrier films.
Without a doubt the RP system offers the best oxygen and moisture
barrier of all available transparent films but from my experience
this would prove far too costly for most archive customers. Some
even find the ArchiPress pouches too expensive and look for cheaper
alternatives. At Conservation By Design we only supply the cheaper
food packaging grade of vacuum bag for use with our "Squelch Drying"
method. With this system the wet books are only intended to be held
for a short time. This kind of low barrier bag is only good for a
matter of months before oxygen penetrates through the plastic.

ArchiPress bags are a 5 layer co-extrusion of Melinex Polyester a
gas barrier layer and Polyethylene and I have held a wet newspaper
for 5 years without any sign of problems. ArchiPress high barrier
bags were designed for strength and to give an oxygen barrier which
would last for years. The Dutch TNO institute tests indicate that
only 10% oxygen will penetrate an ArchiPress bag over a period of 20
years. The choice of barrier films is very important when
considering vacuum packing for long term storage and users should
find out about the oxygen transmission time before choosing a bag.
They should also consider the strength of the bag and how easy it is
to puncture it.

Regarding the question of off-gassing from acid material within the
bag, we advise the inclusion of some form of scavenger such as
MicroChamber paper, Corrosion Intercept, Charcoal Cloth, Charcoal
Felt, or similar to mop up any gases from the enclosed items.

Stuart M. Welch
Managing Director
Conservation By Design Limited
Timecare Works
5 Singer Way
Woburn Road Industrial Estate
Kempston
Bedford
Bedfordshire MK42 7AW
United Kingdom
+44 1234 853 555
Fax: +44 1234 852 334


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                  Conservation DistList Instance 19:46
                 Distributed: Wednesday, March 22, 2006
                       Message Id: cdl-19-46-001
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