I am just back from London, where I had the chance to attend the ‘Paper from the East’ conference at the National Maritime Museum in Greenwich. It is the second Chinese Heritage Conference dedicated to the knowledge of conservation and Museum management of Chinese and Asian Collections, organised by China Culture Connect.
First of all I would like to say that I very much enjoyed all the talks and want to thank the organisers for their efficient and good work.
One of the talk I enjoyed very much and also learned a lot from was entitled ‘Chinese Paintings on Pith – a Paper’s Conservator’s approach’ by Ruth Prosser, private paper conservator in York, England.
Pith paper, also referred to as ‘rice paper’ comes from the inner pith of Tetrapanax papyriferus, a South Asian plant. The pith found on the inside of the plant, is removed by pushing a circular dowel through the branches. It is then stripped into thin slices using a very sharp knife.
In the early 19thCentury Chinese artists adopted this support to paint on and exported their work to western countries. They were first brought back to the West by diplomats as presents and souvenirs. Eventually pith paper became a primary material for the Chinese watercolour market. The pith paintings were generally mounted in silk cover albums, with no signature on the painting itself but were identified by stamps or labels on the album’s cover.
Pith paper is a very fragile material and its surface can easily be bruised. It has a very soft, spongy texture and can break easily. It is also highly reactive to water, probably because it comes directly from the unprocessed plant and has more hemicelluloses and pectin than conventional paper pulp. Pith paper contracts as it ages which leads to cracks in the objects where it has been restrained.
Surface cleaning should only be done using very soft brushes so as not to bruise the painting surface. Because of its high sensitivity to water, pith paper cannot be washed as other papers can, however, slow and controlled humidification can be achieved with humidification sandwich techniques. Reduction of staining is successful using poultices around unpainted areas of the paper and cyclododecane wax around the painted areas as a protective barrier. Pith paper does not like being restrained in any way which can be problematic to repair any tears in the paper the traditional way (Japanese paper and wheat strach paste or methyl cellulose) but the non-fibrous structure of pith paper allow the pieces to be fitted together with only minimal amount of adhesive introduced on both sides of the tears.
As conservators we should keep in mind the different nature of pith papers and other traditional pulp papers, and treat them appropriately.