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.

'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)

A kato alu

This basket from Tonga is No. 86 in the Catalogue of Curiosities, where it is described as 'a strong wicker basket.'

Basket, Tonga - 1886.1.1328

It has been identified by Adrienne Kaeppler, currently the Curator of Oceanic Ethnology at the National Museum of Man, Smithsonian Institution, as a kato alu. These baskets were woven from the aerial roots of a type of climbing vine, the alu, Epipremnum pinnatum, which in it's yellow variegated form (Epipremnum pinnatum 'Aureum' - the golden pothos) is a fairly common houseplant here in the UK.

Alu aerial root surrounding palm leaf midribs

This type of basket is still made on Tonga, although alu is becoming scarce, and is difficult to work.  According to Hettinger and Cox, the aerial roots must be harvested between May and October. Before May, the roots are too small, and after October they have reached the ground. The roots are baked in a pit oven for several hours, until soft, and then soaked in seawater until the outer bark can easily be peeled away. The roots can either be used immediately, or dried in the sun to store them.  Before weaving, the roots are split horizontally twice, and the inner sections discarded. The material is soaked in fresh water for up to two days to make it flexible before use. 

Modern baskets are painted black using soot from burnt tuitui (candlenuts, Aleurites moluccana) mixed with the liquid obtained from the inner bark of the koka tree (Bischofia javanica). On examination of the Pitt Rivers basket, it is likely that the alu was dyed before it was woven. Black dyes in the pacific are often obtained using iron rich mud, and it was interesting that on testing the alu with the handheld XRF (X-ray fluorescence unit) it was found to be rich in iron. We thought that the alu may have been dyed in mud in a similar way. However, further research showed that when dyeing the alu, a brown clay, umea, was often added to the dye mixture. It is also used in a similar way to make black dyed barkcloth on Fiji, where the umea is said to act as a fixative, allowing the dyes to adhere to the cloth. The umea could be the source of the iron.

A damaged part of the basket, showing the core of palm leaf midrib and the decoration of plaited coconut fibre

The basket is made by encircling the alu around a coil of coconut palm leaf midribs. The decoration on the basket is made from plaited coconut fibre. Interestingly, this basket is also decorated on the base.

The base of the basket

The basket has been damaged at the sides, probably by being flattened and crushed in the past. This can be more clearly seen the the photo taken in 1970. To conserve the basket, the broken palm leaf midribs will be supported and the shape of the basket restored.

The kato alu photographed in 1970

Kato alu were used to hold personal items, such as gourds containing scented coconut oil. They were also used for the presentation of such items at funerals and weddings. 

The Making of the Kato Alu: A Traditional Tongan Basket

Amy Lafranca Hettinger and Paul Alan Cox

Economic Botany , Vol. 51, No. 2 (Apr. - Jun., 1997), pp. 144-148

Published by: Springer on behalf of New York Botanical Garden Press

Article Stable URL: http://www.jstor.org/stable/4255942

Baskets in Polynesia, Wendy Arbeit, University of Hawaii Press, 1990