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Subject: Source for tissue for Barrow Laminator

Source for tissue for Barrow Laminator

From: Paul N. Banks <pbanks>
Date: Monday, April 27, 1998
Peter Mecklenburg <artequip [at] frontiernet__net> writes

>The Director of Archives and Historical Research in Tamil, India has
>requested a source of supply of tissues for the Barrow Laminator.

In light of what is now known about the instability of cellulose
acetate in general and the damage to documents from Barrow
lamination in particular, it seems unfortunate to continue to use
this process. It is a variation of one developed by the National
Archives and the National Bureau of Standards in the 1930s and was
patented by Barrow in the 1940s. Barrow's procedure consisted of
deacidifying the document with calcium hydroxide and calcium
bicarbonate, sandwiching it with cellulose acetate film and thin
paper for reinforcing. It was then put through the laminating
machine which softened the acetate in a heating chamber and passed
it through steel rollers to fuse the sandwich.

The heat and pressure involved in the process are obviously rather
drastic treatments in themselves, and at least some of the Barrow
machines had serious problems with control and evenness of
temperature, which caused irregular local overheating. The process
is rather difficult to reverse; Jim Gear at the National Archives
found that a document had to be refluxed in hot acetone to remove
all the cellulose acetate. One archives in the U.S. (I don't
remember which) is in the process of de-laminating documents that
have been found to be deteriorating rapidly.

In any case the Image Permanence Institute's work on cellulose
acetate deterioration strongly suggests that it is not a suitable
conservation material as it deacetylates causing shrinkage and
release of acetic acid. Their work also shows the dramatic
acceleration of this deterioration caused by warmth and humidity.
Although I didn't get as far south as Tamil Nadu during my visit to
Indian archives, I believe that it has a hot, humid climate. Thus
the rapid deterioration of cellulose acetate and consequent
potential damage to documents could be especially serious there
unless carefully engineered and dependable air conditioning is
present in their stacks.

A variation of Barrow lamination, which obviated the need for the
expensive machine, was developed in India by, I believe, Y.P.
Kathpalia. It consisted of fusing the "sandwich" with acetone rather
than heat. This variation avoids the problems of heat and pressure,
but reversibility and acetate degradation issues remain.

Paul N. Banks
560 Riverside Drive #8L
New York NY 10027

                  Conservation DistList Instance 11:86
                  Distributed: Monday, April 27, 1998
                       Message Id: cdl-11-86-001
Received on Monday, 27 April, 1998

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