Encapsulation

Karen Potje <kpotje [at] cca__qc__ca> writes

>What ill effects (if any) might ultrasonically encapsulated paper
>documents (ink and  graphite on paper) suffer if exhibited in an
>uncontrolled environment where the temperature and humidity are
>fluctuating quite broadly.  An institution to which we were planning
>to lend documents is having serious problems with their
>environmental control system.  I have recommended that we not lend
>to them but have been asked if encapsulating all the documents and
>substituting facsimiles for the photographs would make the loan
>acceptable. ...

It is important to note that a layer of polyester film cannot
provide a good moisture barrier. Most plastics are quite permeable
to moisture and gases, hence they are usually not suitable for
creating and maintaining a safe microclimate. With this in mind, the
severity of the temperature and humidity fluctuations in the
surrounding environment, as well as their duration, becomes
important. If these swings are severe enough, very high (or low)
moisture levels could accumulate in the documents.  Adding a
buffering material to the envelope (eg, a rag board backing) would
be of little practical use, and might even exacerbate the situation.

An alternative would be to encapsulate the documents in a true gas
barrier film, (such as Escal film). A suitable microclimate modifier
(a moisture buffer, oxygen absorber, pollutant scavenger, etc.)
could be added to the package for increased protection. Note that
Escal film is very transparent, but is not as crystal clear as
polyester films (Mylar).

More information on <URL:http://www.keepsafe.ca>

Jerry Shiner
Keepsafe Systems / Microclimate Technologies International


                                  ***
                  Conservation DistList Instance 19:29
                 Distributed: Tuesday, December 6, 2005
                       Message Id: cdl-19-29-011
                                  ***