Removing pressure sensitive tape from paper

I am in the process of treating a chromolithograph map from 1890 on
thin, brittle paper that is almost like newsprint.  It has extensive
transparent pressure-sensitive tape on the front and back.  None of
the tape-removal techniques that my colleagues and I have tried have
been satisfactory.  Removing the carrier is difficult because of the
weakness of the paper.  I have been trying to use heat tools: the
Zephyrtronics Airpencil with some success, and a heat spatula with
little success.  The tape and the adhesive are much more cohesive
than the surface of the paper, and so there is a tendency to skin
the surface.  The paper also has the tendency to scorch quickly,
often even before heat from the Airpencil has softened the adhesive
enough to remove the carrier.

For solvents, I have tested water, ethanol, acetone and toluene.
Acetone applied directly with a cotton swab moderately softens the
adhesive to allow insertion of a knife beneath the carrier, though
the paper is still prone to skinning, since the paper loses strength
and cohesiveness just with that amount of moisture.  The inks are
moderately stable with acetone until there is physical manipulation,
like rubbing with a cotton swab.

Removing the carrier is the hardest part.  And after that, the
sticky adhesive residue remains, and the paper is too weak to remove
the residue manually with something like a crepe eraser.  Residue
can be removed with a cotton swab and acetone, but there is still
the problem of ink solubility when touched or manipulated.

I would welcome any suggestions that DistList readers might have for
this problematic treatment.

Grace White
Conservator for Special Collections
Duke University Libraries
Preservation Mailbox #90189
Durham, NC 27708
919-660-5906
Fax: 919-684-2855


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                  Conservation DistList Instance 27:25
                 Distributed: Sunday, December 15, 2013
                       Message Id: cdl-27-25-013
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