Wednesday, 25 July 2012

First voyage barkcloth

This post was written by Misa Tamura, our conservation intern from University College, London.

1886.1.1258 (left), 1886.1.1259 (right)

These two fragments of barkcloth were brought back from Cook’s first voyage to the South Pacific between 1769-1771. These pieces were provenanced to the Society Islands/Tahiti, where James Cook, naturalist Daniel Solander and astronomer Charles Green observed the Transit of Venus in 1769.

Tahitian barkcloth, or ‘ahu was typically made from the bark of the paper mulberry, and the breadfruit tree  as well as two types of Ficus. Barkcloth made from the paper mulberry, characterised by its soft, fine quality with white colour, was worn by people of high rank. According to the museum’s records it is possible that these fragments were obtained in Batavia, Java, Indonesia, during Cook's stopover there in late 1770.  The barkcloth was given to Oxford University in 1883 by Captain D.E.E Wolterbok Muller, of the Dutch Royal Navy Service, who had seen other Cook-voyage objects from Oxford at the 1883 International Exposition in Amsterdam.

Beater marks visible under magnification 1886.1.1258 (left), 1886.1.1259 (right)

The fragments appear to be previously stored folded, perhaps in a similar way the to pile of barkcloth in this image from Tahitian section of the exhibition 'From the Islands of the South Seas 1773–4' held at the Pitt Rivers Museum in 1970.

As a result, the objects now have creases along the folded areas. There were also folds along the edges, which were also a result of the previous storage.

After surface cleaning with a gentle vacuum and a soft brush followed by very gentle application of Smoke/Chem sponge, the creases and folds were humidified using a humidifier and Preservation Pencil at 40 degrees Celsius.

After the humidification treatment, the objects were re-housed into custom-made folders made of acid-free card.

Thursday, 19 July 2012

Investigating objects

Last week, two of our project partners visited us in Oxford.  Professor Richard Evershed from the University of Bristol came with his postdoctoral student, Lucy Cramp, to take samples of resins from various objects in the Cook-voyage collections.  They will use powerful techniques such as gas chromatography, followed by mass spectroscopy to try and give more information about which plant resins were used.  These analytical techniques require very small samples, and, under the microscope, there are usually tiny loose pieces of resin which can be carefully removed using the end of a scalpel blade.

Removing a sample of resin from a chest ornament, Marquesas (1886.1.1269)

Andrew Charlton from the Food and Environment Research Agency (FERA) also came to the museum last week.  Andrew specialises in the effect of pesticides on wildlife, and the purpose of the visit was to work out a method of taking surface swabs from objects so that he can test them for pesticides residues.  We know that objects in the Pitt Rivers, as in all other museums, were routinely sprayed with pesticides, including arsenic, mercury and more recently developed chemicals such as DDT, to prevent insect attack.  We are interested in finding out if there are residues of these chemicals on the surface of museum objects.  The Cook-voyage collections have been in Oxford since the 1780s so we'd expect a wide range of pesticides to have been used on them.

Jeremy with Kloe Rumney, conservation intern from Cardiff University, taking samples from the surface of a Tongan mat (1886.1.1175)

Monday, 16 July 2012

The conservation of a kato alu basket

Some of the objects in the Cook-voyage collections of the Pitt Rivers Museum need interventive conservation work, to stabilise them for display or research.  The Tongan baskets which I've talked about in previous posts are examples of this.  The kato alu in particular has been badly crushed in the past, and the palm leaf midribs that make up the framework of the basket have been broken.  The basket has also become distorted, making any repairs even more difficult to achieve.

Discussing the treatment of the Tongan baskets

Before undertaking a treatment, the conservators at the Pitt Rivers often discuss the options. Sometimes, the general feeling might be that an interventive treatment is not necessary, and that with careful packing and handling further damage to an object can be avoided.  Sometimes though, as with the kato alu, something needs to be done to stabilise damaged areas. 

There were two stages to the conservation treatment of this basket.  The first was to attempt to re-shape it, bringing the broken areas back into alignment.  This was done by making an internal support which allowed the basket to rest upside down.  The basket was then humidified, by placing it in a humidity chamber made from polythene and introducing water vapour, produced by an ultrasonic mister. This uses a metal diaphragm vibrating at ultrasonic frequencies to generate very fine water droplets at room temperature.

The kato alu basket, 1886.1.1328 in the humidity chamber

The vapour is absorbed by the plant material, making it more flexible and easier to manipulate.  The basket was left in the humidity chamber for an hour, and was then flexible enough to reshape gently, holding the new position with pieces of foam tied around the basket with cotton tape.

Reshaping the basket

The basket will be humidified several more times, and the foam adjusted until it has reached a shape more similar to the original.  The breaks in the kato alu will be secured on the inside of the basket with strips of Japanese paper, tinted with acrylic paint to tone in with the colour of the basketwork.  In this way, the broken edges will be protected, and the possibility of future damage or losses reduced.

Friday, 6 July 2012

'Elegant in the Highest Degree'

George Forster notes in 'A Voyage Round the World' in his entries for October 1773 that on Tonga 'these (coconut) fibres were likewise employed in making a great variety of baskets, wrought with regular compartments of two colours, brown and black, or sometimes all brown, and ornamented with rows of flat beads, which were made by cutting bits of shell into that shape.  The taste and the workmanship of these baskets was elegant in the highest degree, and varied into different forms and patterns.' 

1886.1.1330 Kaki mosi kaka, Tonga

This basket, a kaki mosi kaka, is made from dyed and undyed fibres from the coconut husk, leaf sheaths or roots (kaka).  Single strands of the fibre are twined in double pairs to create a very flexible flat basket, said to have been used by chiefly ladies to carry pieces of barkcloth impregnated with scented coconut oil.  The manufacture of baskets of this type ceased in the middle of the 19th century.

1886.1.1130 Detail

The design on the basket, of black and brown triangles, is known as manulua, two birds flying together.  It is a genealogical metaphor for a high-ranking person whose parentage is equally high on both sides.

The basket is made from a single layer of fibre, and is still very flexible,  However some damage has occurred around the handles.  Careful handling and storage should however mean that no interventive conservation treatment is required, apart from surface cleaning.

1886.1.1330 detail of fibre and beads (top-shell, bottom, coconut)