16 Dec 2016

As an intern in paper conservation I had the great pleasure of working on a beautiful and interesting collection of late 19th-century Chinese pith paintings.

Chinese Pith paintings - Detail of one of the paintings under magnification

During the 18th and 19th centuries many port cities of China, especially southern Guandong province, were shipping and trading hubs, with important transport connections to other parts of the country, Japan and Europe.

The profuse traffic of Chinese boats and vessels crowded together on the Pearl River fascinated European travellers and traders, who could immortalize that beautiful view by purchasing watercolours on different supports, including pith, from the various painting studios nearby the port. These painted views were produced in standard sets as souvenirs. They were small, affordable, extremely attractive objects, full of colour and a marvellous velvety texture. They were perfectly complementary to the truly coveted objects of porcelain, tea and silk, whose purchase was the reason many Europeans travelled to China.

Chinese Pith paintings - Before treatment showing the fragile condition of one of the pith paintings

There are 15 paintings in the National Maritime Museum collection representing all sorts of Chinese Junks: duck boats, theatrical troupe boats, salt boats, floating groceries, brothels, luxurious Imperial ships, dragon race boats and fishing and transport vessels, amongst others. Amongst these is a delightful set of 12 miniatures acquired in 1974 and stored in their original box made of silk, hand coloured paper and glass. Unfortunately, the glass lid of the box is broken. The three remaining bigger paintings were housed loose in a poor state, and I have not been able to ascertain it if they even belonged together as a set of three. Two of them retain the usual paper-backed silk ribbon around the four edges and the original Chinese paper backing which, as well as being decorative, offer further protection to these fragile objects.

Chinese Pith paintings - Set of unprotected pith paintings and broken case before treatment

Chinese Pith paintings - Before treatment image with raking light

Pith paintings typically suffer losses and splits or cracks in the support caused by natural brittleness of the pith through aging, and I found that these were no exception. The bigger ones had torn corners due to the tension cause by the traditional mounting method in albums with dabs of glue and silk strips tipped at the edges.

Chines pith paintings - Detail of missing area and split corner before treatment

What is pith?

Pith is often mistaken for rice paper for those unfamiliar with the material. However this support has nothing to do with paper in its structure and behaviour. It´s actually a sheet of inner bark cut from the pith plant, the Tetrapanax Papyrifer. This unusual structure forming such a thin leaf gives the translucent nature and soft surface with its inner velvety texture to the support.

Chinese pith paintings - Honeycomb structure of double walled cells for storing water and nutrients in the plant

The technique

The colours were applied in diverse ways creating marvellous effects between transparency and opacity. Some of the strokes are light washes - the colours cling to the edges of the cell retaining the translucent quality of the support.

Chinese pith paintings - Details of the technique under magnification

Thicker applications tend to fill the cell of the plant, offering a more compact effect as a body colour.

Chinese pith paintings - Detail of the media application with raised glossy outline

I also encountered some additional outlining details, mostly in red and white, raised from the surface providing a 3D effect. These were possibly created by mixing in shellac with the watercolour. I found that these parts are more prone to cracking.

Chinese pith paintings - Another detail of the raised outline effects in vivid red

Treatment challenges

The first challenge I encountered is the extremely fragile character of the pith. Even though pith appears to be similar to a paper, it’s in fact a very thin sheet of wood, and easily breakable. The soft spongy surface is easily damaged. Even the lightest pressure can alter the structure generating every sort of mark and change in the surface.

Chinese pith paintings - Distortions on the support due to high humidity level environmental conditions

In addition, it is extremely sensitive to humidity, expanding and contracting causing severe damage. Also the paints themselves are water sensitive, so it is necessary to avoid any wet treatment or application of direct moisture.

Chinese pith paintings - Detail of a crack in the support under magnification

For the repair of cracks it was essential that I paid particular attention to two things: pith has no projecting fibres to overlap back in place, but rather has sharp edges, and the translucency of the support can make the repairs visible from the front.

Chinese pith paintings - Detail of the verso after repairs with Japanese paper fibres and a thin starch paste

I used a very thin starch paste for mending, combined with trimmed Japanese paper fibres. The non-fibrous nature of the pith allowed me to fit the pieces together like a jigsaw with only a minimal amount of adhesive introduced on both edges. After that, I reinforced the joins by applying fibres (previously moistened in the starch paste), placed in an X shape along the tear, like a seam.

Chinese pith paintings - After treatment showing the repaired pith miniature

Chinese pith paintings - After treatment showing the repaired pith miniature

I was really pleased to have the chance to work with my colleagues from other conservation studios on these objects. To treat the miniature box, the silk was consolidated and the broken glass lid cleaned and consolidated by Anna Rolls, Metals Conservator. I made a support of Plastazote foam to fill the empty case and secure the glass whilst Anna was working on it.

Chinese pith paintings - Original case of the 12 pith miniatures before treatment

Chinese pith paintings - Cleaning the broken glass

The silk ribbons on two of the large paintings were torn and fragile, and I worked with Nora Meller, Textile Conservator. I cleaned the surface and the tears were mended and reinforced.

Chinese pith paintings - Silk ribbons before and after treatment

Chinese pith paintings - After treatment showing paper tabs ready to be mounted

To know more about the mounting and rehousing of the collection I invite you to look for my next blog, coming soon!

Find out more online information about pith there is a very interesting article about the Kew Botanic Gardens collection here

Find out more about pith on the Kew Botanic Gardens collections website (PDF)

More about conservation at Royal Museums Greenwich

Goizane Mendia Rios, Assistant Paper Conservator