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Subject: Interleaving

Interleaving

From: Cor Knops <corknops>
Date: Thursday, January 18, 1996
Elaine Smyth <notebs [at] lsuvm__sncc__lsu__edu> wrote :

>The type of
>"offsetting" that I am describing might more appropriately be called
>staining or image migration.  It is associated with dark pigments
>(grays, blacks, and browns are the worst) used in the hand coloring.
>It affects more than the plate immediately adjacent to the image, in
>the worst cases.
>
>My questions are: is this likely to be a continuing process after
>160 years? If it is, will interleaving do any good?  If interleaving
>would not be effective, what else might be done?

The case I had might be somewhat similar to your problem. The book I
was confronted with was a handcoloured Maria Sybilla Merian,
Methamorphosis Insectorum Surinamensium, dated 1705 (1st ed.). It
consist of 60 large folio engravings which are coloured by hand.
Since it deals with insects and the plants they live on and from, a
lot of green colours are used. In particular these green pigments
showed extreme migration and discoloration. The copper pigments used
in the paint had damaged not only the paper they were on (resulting
in brittleness and little cracks) but also affected the adjacent
pages and in some cases even the next page as well. The paper gets
brown at these spots.

Of course what happens here is a chemical reaction; not a physical
or mechanical transfer of pigments or paint. In this case the
process continues, even after 290 years. In fact this continues
until all of the copper is rendered to it's brown product.

The problem of how to cure this damage is complex: until now there
doesn't seems to have been an appropriate method to (chemically)
stop, neutralize, or reverse the process. Methods which are
available do actually take out the damaging component, but by that
take the colour away as well. In the case of this (rare and
important) book, this was no option; the green (and some of the
blue) had to be coloured in again afterwards. Besides that, the
whole book had to be taken apart and the pages had to be
"wet-treated", with all the consequences. From an ethical point of
view, and thus trying to keep the integrity of the book preserved, I
had to think of something else.

Interleaving was (for this particular book) the best solution.
Because of the fact that the spine of the book was broken (or at
least nearly broken) it had to be taken off anyway.

The back of the book was covered with spine lining for
reinforcement. These were taken off also. Now the back was accessible
for further treatment. The old (animal) glue was removed as much as
possible. All this was necessary to create some space for the
interleaves; because I had to put in 30 leaves of paper, the
swelling would be 5 millimetres. The interleaves were mounted with a
few tips of starch on the outer folds of the sections. The size of
the paper was a little smaller than the pages of the book, so it
doesn't affect the visual nature of the edges.

The paper I've used was new to me: MicroChamber (this paper is
discussed on this list before and available from Conservation
Resources, info from Mark Vine, also on this list). Because the
problem I was facing was a typical migration of metal ions, this
paper, which claims to "trap" these ions by molecular sieves which
are built-in in the paper using active carbons, this material should
at least stop the process of discolouring the adjacent pages.

Of course it won't stop the the actual process within the copper
pigment, but maybe in a few years time our much-belauded scientists
will come up with a non-destructive treatment. By that time the
interleaves can be taken out without damaging anything and I can
proudly say: at least I didn't ruin the book.

Cor Knops
Knops Boekrestauratie
Groenstraat 8
6151 CS Munstergeleen
Netherlands
+31 46 529643
+31 46 511822
Fax: +31 46 529643

                                  ***
                  Conservation DistList Instance 9:56
                Distributed: Thursday, January 25, 1996
                        Message Id: cdl-9-56-007
                                  ***
Received on Thursday, 18 January, 1996

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