Library of Congress manuscript marking ink

For the past several years, the Preservation Directorate has
provided free samples of its manuscript marking inks to curators of
paper-based collections.  Recently, one of the recipients of our ink
samples brought to our attention that the stamped impression was
smudged by alcohol. Our Preservation Research and Testing Division
confirmed this observation, although they also found that most of
the ink remains firmly affixed to the paper.  Therefore, we would
like to warn other users of our manuscript marking inks that any
future conservation treatment of items stamped with these inks
should take into account the fact that they contain a significant
fugitive component that can be removed by several common solvents.
Nevertheless, the stamped ink impression cannot be completely
removed by any means without causing significant damage to the
paper.  That is, the objective of providing security for the items
stamped with these manuscript marking inks has not been compromised
in spite of the removability of a part of the stamped impression.

The indelibility of the LC manuscript marking inks derives mainly
from the small particle size of the pigments used in their
formulation.  The particle size is so small that these pigments
penetrate into the fiber structure of paper.  Therefore, these inks
cannot be removed from paper without causing noticeable damage.  The
fact that some of the stamped impression can be removed by solvents
means that some of the pigment particles are so large that they
remain on the paper surface instead of seeping into the fiber
structure.  Either the particle size of the pigments has grown
during storage due to agglomeration, or the pigment used by the
Government Printing Office in the manufacture of the inks did not
meet the specification for their formulation.  Evidently, we need to
investigate this problem.  Until a fail-safe solution is found, we
shall reluctantly *discontinue the supply* of the manuscript marking
ink samples.

Chandru J. Shahani
Chief, Research and Testing Division
Library of Congress

                                  ***
                  Conservation DistList Instance 9:74
                   Distributed: Thursday, May 9, 1996
                        Message Id: cdl-9-74-001
                                  ***