Conservation of pith paper

Julia M. Landry <j.landry [at] ns__sympatico__ca> writes

>Does anyone have any experience working with Chinese pith paper,
>often mistakenly called rice paper.  I'd be interested to receive
>any information on its physical properties, etc.

I have treated various watercolours on pith paper and have found
that while the pith is extremely brittle when dry it becomes quite
elastic and supple when damp. This means that repairing tears and
reattaching loose pieces is much more simple than it seems at first
glance. I have found that repairs are best made with 3% sodium
carboxy methyl cellulose (CMC) in water. If the pith is misshapen
and the join does not match perfectly it can help to slightly wet
the edges of the join before applying the adhesive. If the join does
match well this is probably not necessary. If reinforcement on the
back is necessary (it often isn't) i have used tengujo paper and 3%
CMC in water. The repairs can be left to dry between polyester web
and blotters under a light weight--too heavy a weight will squash
the damp pith.

I would not advise dampening the whole object to flatten it. The
undulating surface of many watercolours on pith paper is partly due
to the way the pith expands when the media is applied, and is partly
due to the uneven shrinkage of the pith as it ages. Additionally,
the potential for expansion and contraction of the pith during
dampening and drying, and the possible effect of this on the media
on the surface means that even though the pith might be able to
handle it the object as a whole probably cannot. It is sometimes
necessary to flatten really crumpled areas but it is probably better
to do this in small areas at a time.

Brown stains in the pith seem to move fairly easily when dampened. I
have not had reason to 'wash' pith paper but suspect that  cleaning
with water--local application to stains only--would probably be
successful on the vacuum suction table.

I have gathered together various articles and books on the history,
production and treatment of pith paper. If you require this sort of
information please let me know.

Carolyn Murphy
Conservator (Works on Paper)
Queensland Art Gallery
Brisbane, Australia



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                  Conservation DistList Instance 13:48
                  Distributed: Friday, March 24, 2000
                       Message Id: cdl-13-48-009
                                  ***