Leather chariot cover

Lucy Skinner <lucy.skinner [at] gmail__com> writes

>I have found that Klucel G 1% in ethanol consolidates the powdery
>flesh surface very effectively without darkening. However, the
>leather becomes stiffer following consolidation which is not a
>favourable property when I wish to remove creases from a fragment.
>Both pre and post-consolidation, I have been placing the leather in
>an ethanol saturated environmental chamber to try to soften the
>fibres. This does soften the leather slightly to allow some
>manipulation and unfolding but the technique is not especially
>effective. Any suggestions for alternative consolidants or treatment
>to strengthen the leather without stiffening it, and a more
>effective technique for unfolding the leather without using water
>(humidifying would I believe be fatal for the degraded leather),
>would be greatly appreciated.

When I select a consolidant for the stabilization of a degraded
leather binding Klucel G is a good choice for the areas that do not
need to flex. Its small molecular weight in combination with ethanol
allows good penetration of the leather substrate with little colour
change, but it is the very nature of a consolidant being an
adhesive, fixing and stiffening the leather, that makes it a poor
choice for the flexing areas of a book; the joints and spine. In
these areas a book conservator reaches for more flexible adhesive
consolidants, like the Leather Conservation Center's SC6000 cocktail
or Lascaux 498 HV in 2-propanol (iso-propanol). These acrylic resins
are much larger molecules so you trade off penetration with
flexibility and there is a danger of the material remaining on or
near the surface rather than penetrating to the required depth. The
SC6000 cocktail was developed at Harvard University Library and is
an equal mix of Klucel G in ethanol, SC6000, and ethanol.

Over the last few years I have been replacing ethanol with
2-propanol in my consolidant mixtures, I feel it is one step further
away from water. You can prepare Klucel G in 2-propanol with some
patience and the alcohol should be available without trouble in
Egypt, the mix is available commercially under the name of Cellugel
I think, but I make my own.

Just a last word about consolidation of leather in general, in book
conservation it has a rather uncomfortable history with many
materials used to "dress" the leather. It is still done if necessary
with modern materials as a conservator realizes a book will be
handled opened and read regardless of age, so a calculated risk is
taken. I have no idea how old your Egyptian fragments are but I'm
pretty sure you will not using them to make a cover for the Museum
director's car. A leather that has survived this long must generally
have good chemical stability regardless of its seemingly low pH,
unless it has been affected recently by some external pollutant. Is
it actively powdering and delamination or is the problem stiffness
and brittleness, I rarely see both together? If, after conservation,
you can remove the source of the pollution with a controlled
filtered environment on display and provide supporting
storage/display mounts perhaps there is no need for consolidation?
If you are in Cairo it is a very busy and polluted city. You should
also be concerned about what materials you are permanently
introducing to an object, you may affect any future analysis of the
leather.

If you still feel that consolidation is necessary perhaps try to
gently open the fold during the window between application and
setting of the adhesive, a little bit at a time. Doing this while in
your ethanol environmental chamber seems sensible, if you take care,
Lascaux can be warmed gently with a hot air pencil or small travel
hair dryer to soften it and Klucel G can be remoistened by the
solvent it was prepared in. Taking little steps at a time you may be
able to open the folds and reset them. If nothing is satisfactory
there are these days quite advanced 3D digital soft ware which can
digitally unwrap your object, perhaps one of the companies can be
convinced to loan the technology if they are insufficient funds to
obtain it for your project.

Neill McManus
McManus Paper Conservation
25 Haprachim St.
Rishpon 46915
Israel
+972 9 9506905



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                  Conservation DistList Instance 25:22
                 Distributed: Monday, October 31, 2011
                       Message Id: cdl-25-22-001
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