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Re: [BKARTS] repair tissue

On Sat, 17 Apr 2004, rob wrote:

> Dear Folks,
> I am going to buy tissue for repairing paper tears along the edge of
> paper and where signatures are folded. As a first-timer I have found a
> few sources but have a few questions.
> There is Japanese tissue vs pressure or heat sensitive tissue, what are
> the concerns/benefits about using one over the other?

I'm sure those more experienced than I will have much to add, but I'll
toss my 2 cents in.

Using an appropriate japanese tissue and wheat starch paste means that
your repairs are fully reversible, using only water.  And the archival
stability of these materials has been tested through centuries of use, in
addition to scientific testing.  Before the paste dries, it's easily
repositionable.  The downsides are that you have to introduce water,
which can lead to tide lines, can mobilize water-soluble inks, and means
you have to let the mended paper dry under weight before doing anything
else with it, and it's difficult to get good adhesion on glossy paper.
This is the type of mend the conservation lab I work in uses most often,
particularly when guarding folds.

Heat-set tissue is theoretically reversible with re-application of
heat, but in practice it's tricky to do without fiber loss.  Since it
doesn't introduce moisture, it doesn't require drying time.  The
adhesive is not tacky when cool, so doesn't have the same type of
migration problem that pressure-sensitive adhesives are known for.  Some
materials don't respond well to heat.  If you use heat-set tissue to fill
in missing areas of paper, you need to do it from both sides so as not to
leave adhesive exposed.  The tissue is totally repositionable before
heat is applied, not at all after.  The lab I work in usually uses
heat-set in repairing less significant modern materials.

Non-archival pressure-sensitive adhesives have a history of being terrible
for long- or even medium-term use; because they stay semi-liquid, over
time they can migrate into and embrittle or discolor paper, mobilize
inks, and eventually lose their adhesive ability and release the support.

There seems to be considerable skepticism among conservators about the
pressure-sensitive mending tapes labelled "archival"; the lab I work in
uses them for temporarily mending materials for photocopy replacement, and
in the construction of enclosures, but not directly on materials intended
to be permanent.

> There are a dozen different Japanese papers - any one or two
> recommendations?

I'll leave that to others to answer, since I haven't had much chance to
compare different ones.

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