Ray skin

I am currently working at a table made by Jules Leleu in Paris in
1931. The plate is glued with a thin, almost transparent ray skin
that is coloured green and has a powdery white layer from
underneath. This white layer is a lacquer based on shellac and
sandarac. The pigments are lithopone and chalk. In publications only
coloured paper or textile under the skin is mentioned but no
pigmented layers. The glue between wooden plate and white layer is
most likely sturgeon glue (determined by the infrared spectroscopy
analysis). There were also found some hints for a synthetic product
like polyacrylate are found. It is not exactly analysed.

The problem is that the ray skin dissolves from the wood plate at
several points. Normally this kind of furniture of that time period
is very stable and shows no damage at all. I suppose that the
delamination at this table takes place because of the two different
binding systems of animal glue and spirit varnish between ray skin
and wood plate.

Has anybody ever recognized a pigmented layer at the backside of ray
skin glued on furniture or similar objects of the Art Deco? May this
be a technique typically used by Leleu? Has anybody any experiences
refixing ray skin in combination with these materials, or at least
any suggestions? At present I would prefer a sturgeon glue as it
will fit with the original. The disadvantage of keeping to the
original system may be that the skin could dissolve again.

Birte Koehler
Conservator
Museum fuer Kunst und Gewerbe Hamburg
Steintorplatz
20099 Hamburg
Germany


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                  Conservation DistList Instance 20:35
                 Distributed: Monday, January 15, 2007
                       Message Id: cdl-20-35-016
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