Monday, 27 February 2012

A Loan to Whitby

Heather Richardson, Head of Conservation at the Pitt Rivers Museum, recently couriered some objects from our Cook-Voyage collections to Whitby.  She writes:

'The Pitt Rivers Museum has just loaned 12 Pacific island objects to the Captain Cook Memorial Museum in Whitby, North Yorkshire, for the temporary exhibition “Eating the Exotic”. Ten of the twelve objects related to food are from the Cook voyages, nine from the Forster Collection and one from the Banks Collection. They include fish hooks, a kava bowl and a fern root beater.
Prior to sending objects on loan conservators must check that they are suitable to travel and then prepare condition reports detailing all existing scratches, accretions or other markings. The conservators then pack the objects securely into crates lined with inert foam to cushion the objects while in transit.

Fish hooks packed in cut-outs in the foam near the top of the crate

Eleven of the objects travelling to Whitby fitted into an existing packing crate and a new crate was made to transport the large Tongan mat made from hibiscus fibre with Pandanus decoration (1886.1.1177) detailed in an earlier blog posting. Instructions on how the crates are packed and unpacked were also compiled.
On Monday 20th February the crates were loaded onto a special truck with air ride suspension and securely strapped in place by the drivers, who were both experienced art handlers. As with all loans of objects from the Pitt Rivers a courier then travelled with the objects throughout the journey from Oxford to Whitby, which took six hours.
The Captain Cook Memorial Museum is situated within a 17th Century harbour-front house and is where James Cook was apprenticed to Captain John Walker in 1746.

View from the garden of the Captain Cook Memorial Museum.  A replica of the Endeavour is in the foreground, which is about 40% of the ships original size

The attic where Cook stayed as an apprentice is now used by the museum for temporary exhibitions.  On arrival at Whitby the crates were unloaded and carried down Grape Lane to the museum, which is too narrow for vehicle access. The crates proved marginally too wide for some of the very narrow doorways of the house, so the objects were carefully unpacked in a room on the ground floor and carried up the narrow stairs to the attic.
Over the next two days the objects were checked against the condition reports to ensure no new damage had occurred during transit, before positioning them in three display cases.

A case containing kava bowls and a Tongan mat from the Pitt Rivers

While designing the layout of the display cases labels were also checked for the correct attributions and positioned inside the cases. All three cases needed to be securely locked before the courier was allowed to depart on the 22nd February.

A large shark hook from Tahiti, part of the Banks (First Voyage) collection
The exhibition will open to the public on 1st March and run until the museum closes for winter on the 31st October 2012.'

Thursday, 23 February 2012

Hunting for Crystals

A significant part of the project to investigate the Cook-Voyage collections at the Pitt Rivers is to attempt to identify some of the materials used to produce the objects.  Over the years, there have been many informed guesses about what materials are present, but no physical identification has been carried out on the majority of the collections.  Once materials have been identified, it is possible that they may have some characteristic that could help identify similar material in future.  One of these is the presence of crystals in plant cells.  These crystals, or phytoliths, are found in many plant species, and their presence could be one of the features that allows for a positive identification of a sample.  Phytoliths are commonly made from calcium oxalate, but other crystals have been found that contain silica.

This week I took samples of plant material from two objects to Dr. Debra Carr at Cranfield University.  Deb has worked extensively on methods for characterising plant fibres, particularly those used by the Maori (see for example her article 'Approaches for Conservators to the Identification of Plant Material used in Maori Artefacts'  in Studies in Conservation Vol.53 (2008)  The samples I took to her were from Tahitian objects.  One was a piece of aerial root from a type of palm (Freycinetia sp.) that was used to stabilise the structure of the cloak from the Mourner's costume (1886.1.1637 .4).  The other was a piece of hibiscus (Thespesia populnea) fibre from a woven mat (1945.11.130).  Both samples had already been identified, and Deb was interested to see if they contained phytoliths.

The samples were first examined by X-ray diffraction (XRD).  This technique allows for the identification of materials with a regular crystalline structure by focusing a beam of X-rays onto them.  The X-rays are diffracted by the crystals and the diffraction patterns detected and analysed - these are characteristic for different crystals.  The small size and dispersed nature of many of the phytoliths in plant material means that it's hard to detect them using this technique, although it was possible to say that there were crystals in the samples.

The sample of Freycinetia in the XRD machine

Next, X-ray fluorescence (XRF) was used to examine the samples.  Again, the sample is bombarded with X-rays.  The elements within the sample release energy when they are excited by the X-rays, and the amount of energy released is characteristic of each element.  The XRF machine at Cranfield can build up an image of the sample, mapping out where the different elements of interest, such as calcium in this case, are located within the physical structure.  Again, there was some evidence, particularly in the sample of Freycinetia, that calcium was present just under the epidermis of the aerial root, where the presence of crystals might be expected.

Dr. David Lane carrying out XRF analysis
A map of the elemental composition of the hibiscus fibres obtained from the XRF

Finally, we looked at the samples under the electron microscope to see if we could visualise phytoliths within the plant structure.  The microscope uses a beam of electrons to illuminate the sample and to provide the image, and has a much greater resolution that a light microscope.  Although I was surprised at how much of the physical plant structure remained after nearly 250 years, we did not conclusively find crystals in either sample. 

Looking at the hibiscus sample under the SEM

It's possible that with more time we could find phytoliths within the plant material, and this would help us carry out identification in the future.  It's also possible, particularly in the case of the hibiscus mat fibre, that the way the fibre was processed before being woven, by being soaked in seawater for several days, could have removed any evidence of phytoliths.

Tuesday, 14 February 2012

A Tongan Fishing Net

The Forster collection at the Pitt Rivers includes a fishing net from Tonga, 1886.1.1426.  It is No. 60 in the 'Catalogue of Curiosities sent to Oxford', where it is described as 'a fishing Net'. It is possible that the net has not been fully opened up in the museum before as its length has never been recorded.

The net photographed in 1970

The net when taken out of storage last week

Small coral stones, used as weights,  are tied to a coconut fibre cord which forms the bottom edge of the net. The top edge of the net uses coconut fibre cord to tie in pegs of a lightweight wood, possibly hibiscus,which act as floats.  The net was made from a fine, two-ply plant fibre cord with a netting needle. The mesh was knotted around a gauge which was used to keep the mesh size even and regular.

Detail of the mesh

This net would have been made communally by  a whole community, and would have been kept by the chief.

Last week I  opened the net up and stretched out to its full size, which is about 8m long by 1.1m wide.

The net stretched out in the lab

The main conservation issue with a net of this size is how to store it.  If they are folded, nets become tangled, and are not easily available for study.  We decided to attach the net, by sewing around the edges, to a conservation approved backing material and to roll it for storage.

The net after sewing to a backing fabric

Tuesday, 7 February 2012

A Tongan Skirt

In the last few weeks, I've been working on a Tongan skirt from the Forster Collection (1886.1.1177). The skirt is no.55a in the 'Catalogue of Curiosities', and is described as 'a matt with red stripes'.

The skirt was thought to have come from New Zealand until the Catalogue was rediscovered in 1969, which has confused the identification of the materials from which it is made.

The skirt is decorated with red and white tags made from short lengths of plant material, about 5cm long.

The red tags on the skirt, before conservation treatment

The tags have been wound around one of the strips of an outer weft where it crosses an inner one, which had to be done as the skirt was woven, leaving two 2cm long tags on the front. The tag is not visible on the inside of the skirt, and it is firmly held in place by the structure of the weaving.

Two tags, red and white, seen from the back of the skirt

Part of the 'Conserving Curiosities' project is to attempt to identify some of the plants used to make objects in the Cook-Voyage collections. Over the years there have been many suggestions about what the skirt was made from, including New Zealand flax, lacebark (a tree, also from New Zealand) and Pandanus palm. Very small pieces of the plant material from the skirt were sent to Dr Stephen Harris, Druce Curator of the Oxford Herbaria, for identification. He discovered that the skirt itself was most probably woven from the bast fibres of Thespasia populnea, a hibiscus-like plant found throughout the Pacific. Both colours of tag were identified as being made from the leaves of the Pandanus, although the leaves used to make the red tags were much more heavily processed before use, with just the outer layers of the leaf remaining. The samples were boiled in water during the identification process to rehydrate them, and Dr Harris noted that the red sample retained its colour when boiled, indicating that it was probably not dyed with a water soluble dye or pigment - interesting as the red dyes of the time were plant based and would be expected to be water soluble.

The skirt needed many hours of humidification with an ultrasonic humidifier to allow the brittle tags to be unfolded and opened up where they had become creased.

The skirt is being loaned to the Captain Cook Memorial Museum in Whitby, with several other Cook-Voyage objects from the Pitt Rivers, for their special exhibition, 'Eating the Exotic!' which opens in March.

Wednesday, 1 February 2012

Tongan Mats

There are several examples of finely woven mats from Tonga in the Cook-voyage collections at the Pitt Rivers Museum.  The mats were woven (or, technically, plaited) by women, and were used for many different purposes.  Large mats were used as sails for canoes  - a link to an article from the British Museum discussing the conservation of a unique matting sail, but from Tahiti, can be found here:

More finely woven mats were used as clothing, and could be valuable commodities amongst the people of Tonga.  Indeed, these mats have been described as ‘the most important and powerful objects in Tonga…heirlooms passed from generation to generation as treasures…objects of prestige and power’ * They were made from the leaves of the Pandanus palm, of which there are several types.  The leaves need to be prepared for weaving by stripping off the thorny edges and the point and bleaching in the sun, or possibly in seawater, depending on the type of Pandanus. The leaves are split into strips for weaving.

The Pandanus strips used to weave the mat

Deep creases are present in the mat, a result of folding for storage
The mat I am currently working on is described in the ‘Catalogue of Curiosities’ as ‘No. 54  a small smooth matt’ .  It is made from Pandanus strips 2-3 mm wide, and its dimensions are approximately 168 x 132cm.

The mat has been folded for many years, so that the fold lines have become deep creases. It is possible to humidify the mat, using an ultrasonic mister, to make the creases in the mat less pronounced.

The mat is still very soft and flexible, which makes the process easier.  While working on the mat, I found an area that had been carefully repaired while the mat was in use on Tonga, showing that their owners valued these objects enough to spend the time skilfully weaving in a patch to cover the hole.

The mat partially humidified, showing the
Forster label (No.54)

The repaired area on the mat - the repair
is even less noticable on the other side

 *Kaeppler, A. ‘Kie Hingoa: Mats of Power, Rank, Prestige and History’, Journal of the Polynesian Society, Vol 108,  no.2, 1999