Consolidating deteriorated leather

I'm doing some practical research on the treatment of degraded book
leather. One problem that I frequently encounter is that vegetable
tanned leather (calf mostly) has become crumbly and powdery due to
hydrolytic or acid deterioration. The problem occurs not only on the
"known" problem books bound in the late 19th century (the so called
"red-rot"), but also on a lot of books dating from the 16th - 18th
centuries.

The phenomenon can be described as the leather being deteriorated
because of broken molecular chains, resulting in the transfer of
leather-particles. In the daily routine of libraries where books
like this are consulted, the leather is touched with bare (moist)
hands and a fine brown dust sticks to your fingers. When the book is
opened thereafter this dust is smudged on the paper. Due to the same
deterioration, the upper layer of the leather is mostly very brittle
and comes off very easy.

In searching for a solution in the past I came up with several
non-aqueous adhesives and various ways of fixing and consolidating
this type of leather. From a conservator's point of view
(reversibility, aging. stability, etc.) most of these consolidants
where not appropriate to use in conservation. Besides that, some of
them where very unpleasant and hazardous to handle.

Right now I use solution of 4% hydroxypropylcellulose (Klucel E) in
ethanol 96% or acetone. This solution is applied by spraying on the
the powdering areas of the book cover. The results are very
satisfying:

    *   no discoloration (blackening, "burning" of the leather)

    *   good fixing with very small quantities

    *   reversibility (HPC is soluble in water, but how to 'wash' it
        out of the leather I don't know)

    *   chemical stability, and

    *   no appearance of shine or glow.

But, there's one problem: some type of book covers are partially
blind-tooled and in the tooled areas, the leather is harder and more
compressed. The HPC-spray does not penetrate in these parts; it
forms a thin layer on top of it. When touched with (again, moist)
fingers the HPC gets sticky immediately and when you lift your
fingers you'll notice little parts of the stamps on your skin. Of
course this is not what I intended.

I have been doing some experimenting with other types of cellulose
ethers in order to overcome this problem, but so far this has not
resulted in a good workable spray.

My questions to you are the following :

    *   Does anyone have any experience with this problem in
        general?

    *   Does anyone use something different then cellulose
        derivatives?

    *   Has anyone ever tried to dissolve wheat-starch in an organic
        solvent? (I did but the solvent (dimethylsulphoxide) is very
        bad for your health)

    *   Does anyone know anyone who is investigating on this matter?

Any answers to my questions or other suggestions are very welcome,

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

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                  Conservation DistList Instance 9:19
                  Distributed: Monday, August 28, 1995
                        Message Id: cdl-9-19-004
                                  ***