Gum arabic and Japanese masks

In Conservation DistList Instance: 12:77, Wednesday, March 31, 1999
Pawel Karaszkiewicz asked if it was possible to find gum arabic as
an additive in the painting of a Japanese mask.

In my opinion, it is usually difficult to identify polysaccharides
(gums and mucilages) used as pigment binders by IR analysis.
Although the painting may contain a polysaccharide, it may be
difficult to tell if it is starch or gum arabic.

Besides gum arabic there are several other polysaccharides that have
been used as adhesives and pigment binders. For instance, tragacanth
gum, cherry gum, tamarind gum, mesquite gum, etc. Apparently, the
only way to differentiate gums is by means of chromatography.

In Mexico the mucilage extracted from orchid bulbs was used as an
adhesive and as a pigment binder. One of the methods of preparation
of the orchid adhesive was to grind the dry bulb into a fine powder.
The powder contained about 7% starch. This powder could be stored
for some months. The powder was mixed with water and used as an
adhesive or pigment.

I know that an adhesive extracted from orchid bulbs was also used in
Japan, specially in the southern islands. This orchid mucilage was
used as an adhesive and pigment binder in Australia and in south
east Asia. I don't know how the adhesive was prepared in Japan,
however, if they used the same method used by the ancient Mexicans,
it is possible to find starch and a gum in a same sample, both from
the orchid bulb.

Carolusa Gonzalez Tirado
Escuela Nacional de Restauracion
Churubusco, Mexico

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                  Conservation DistList Instance 12:79
                  Distributed: Tuesday, April 6, 1999
                       Message Id: cdl-12-79-002
                                  ***