Conservation of the Rushbrook Coffer at the V&A Museum

Having finished up our term at UCL, Alison and I were suddenly aware of a long empty summer ahead of us with no conservation work to do! Luckily the timing worked out perfectly as Shayne Rivers, V&A Furniture Conservation Department, needed some interns.

We feel very fortunate to have been given the opportunity to work with Shayne on a wonderful example of 16^th century Japanese export lacquer. The Rushbrook Coffer is due to be exhibited on open display within the galleries in late November and required essential consolidation to stabilise the failing mother of pearl shell inlay, lacquer and foundation layers. Japanese export-ware is typically constructed from a cheaper animal glue-based foundation, rather than using the more expensive urushi (lacquer). It is this cheaper animal glue layer that is failing on the coffer and causing the loss of shell and lacquer decoration.

Rushbrook Coffer (PHOTO:V&A)

The treatment of this object has been a balance of considerations for Shayne and her colleagues. Extensive testing was undertaken before we began our internship to assess the impact of different adhesives and solvents on the shell, with regards to penetration, adhesion and visual appearance. After assessing the results, a Japanese hide glue (applied as a warm liquid with a small amount of IMS added to reduce the surface tension and aid penetration) was used as the consolidant. This was an unusual choice for aged lacquer, which is increasingly susceptible to swelling/dissolution by water, and to possible discolouration by a combination of heat and moisture. However, following the extensive testing the hide glue was in fact seen to cause the least visible change to the appearance of the thin shell inlay, whilst also providing adequate adhesion of the failing layers. Collagen based adhesives were a new material to both of us but we were able to expand our knowledge of the chemistry involved in their manufacture and use thanks to directed reading from Shayne.

Nikki and Alison, placing the fibreglass Shimbari sticks between the silicone pads and wooden frame.
(PHOTO: Shayne Rivers)

Previous conservation treatments of the Rushbrook Coffer have been restricted due to the difficulty of applying force to the coffer, in order to relay the loose shell. By using a traditional Japanese technique this difficulty has been overcome. A Shimbari frame has been built around the coffer, into which hardwood beams can be moved to the correct height and angle. Shimbari sticks are then utilised to apply suitable pressure to the newly consolidated areas, we substituted the more traditional bamboo lengths with fibreglass (which, unlike bamboo, continues to exert pressure over time). A ‘sandwich’ of warmed silicone, Perspex and PVC pads was used between the coffer and the sticks to encourage further penetration of the glue (heat), act as a release agent (Silicone), spread the pressure and provide cushioning (Perspex and PVC).  It is enlightening to be using this traditional Japanese approach and are both now thinking of other conservation applications for this wonderful technique. In fact, this will be the subject of a paper soon to be written by a member of the V&A Furniture Conservation department in the near future. 

 Alison cleaning a recently consolidated area of shell.
(PHOTO: Shayne Rivers)

While we were invited to the V&A to help Shayne consolidate the coffer for exhibition, she also generously allowed us to investigate other areas of the coffer and expand our skills in varnish removal and retouching.

With the assistance of Shayne, a UV light and the undertaking of solvent cleaning trials. We were able to identify the disfiguring modern coating on the coffer as a Ketone N resin, which was readily removed in xylene without causing blooming or other damage to the lacquer. Although exposing a more matte and aged lacquer beneath, the removal of the coating is considered both desirable and necessary in this instance as the unsightly, shiny and uneven appearance of the surface in no way reflects the original appearance of the un-aged lacquer. Removing this coating whilst still readily soluble in a non-polar solvent will also prevent future damage to the lacquer or shell.

Identifying a suitable retouching medium for the lacquer losses, involved trialling a number of conservation-grade materials including Gamblin paints (urea aldehyde), Golden acrylics (solvent-based) and Paraloid B-72 in xylene.  Gamblin’s “Black Spinel”, with the application of a top layer of 30% w/v Laropal A-81 in xylene, proved to be the most suitable match for the aged Rushbrook lacquer in terms of colour, saturation and gloss, as well as being photochemically stable and readily removable. However, once this colour was tested on the coffer it was clearly too glossy in comparison to the cleaned matte lacquer surrounding. Looking back to our paint samples we chose a more matte “Ivory Black” to test on the object, this time securing a good colour match. Unfortunately, the retouching was seen to be more black/matte when viewed from the side in raking light. However, we still believe this to be the most suitable retouching medium for the coffer. Any retouching on the coffer would be undertaken to ease an interpretation of the decoration and will be considered once consolidation has been completed, depending on time constraints.

As previously mentioned, Shayne was kind enough to allow us to work on other aspects of lacquer conservation. For one separate, but associated, project, we undertook the assessment and brief treatment of a Korean lacquer box, also with shell inlay, due to be sent on loan. Through working on this object we were able to put all the reading we had completed into practice, which really helped cement the different principles we had taken from the articles.  However, practice still makes perfect as we incorrectly identified the bright orange auto-fluorescence (under UV) of the box as more reminiscent of a shellac coating or western coating.  Further investigation with a microscope revealed metallic flakes close to the surface, leading to the identification of  ‘Nashiji’ decoration (relatively large, dispersed metal flakes beneath a tinted lacquer layer), which is also characterised by its bright orange fluorescence.

Large scratches on the surface of the box and a lack of micro-cracking caused photo-degradation suggested that the box had been previously polished down, partially removing the uppermost tinted lacquer and exposing the metal flakes and underlying lacquer layer/s. It is unclear how much light damage had affected the box before polishing as well as the extent of lost decoration. What is clear is that the box has no gold decoration remaining and the gloss that can be seen is a result of the polishing undertaken.  

The box required cleaning with white spirit and toluene to remove greasy dirt and polish residue around the metal plate and brackets. Water-based cleaning was not attempted in this instance due to the damage that could be caused and the possible loss of remaining Nashiji flakes.

ABOVE: Crackline, identified as in need of consolidation.
BELOW: Shimbari frame used to apply pressure after consolidant was introduced.
(PHOTOS: Shayne Rivers)

Localised consolidation was required along stress fractures (where separate wooden elements of the structure meet, orientated in different directions and thus differentially moving with fluctuations in RH). A small Shimbari frame was used to apply pressure to the consolidated areas, this time without the use of heated silicone, as the consolidant chosen, PVAC Mowilith 50, does not become less viscous with heat. Mowilith 50 was chosen because of it’s solubility in the non-polar solvent Toluene,  it’s low pH as a dry film and it’s relatively flexible, properties necessary to minimise any further damage to the aged lacquer.    

Overall, this short internship has proved to be a really wonderful experience, and a (very) steep learning curve. Shayne has been generous with both her time and expertise, providing  us with extensive reading to extrapolate the ‘principles’ of multiple topics including the nature, deterioration and conservation of lacquer, the properties of glues and retouching mediums, an introduction to fracture mechanics and how it relates to decorative surfaces and conservation applications... we could go on...!  The reading has equipped us well to assess and understand the deterioration mechanisms of the objects we have been working on, and to propose suitable treatment methodologies. We feel privileged to have had this opportunity, and a tiny bit jealous of those who benefit from her instruction in the longer term! Our conservation understanding has come on in leaps and bounds and we are now looking forward to applying the principles and methods to other objects during our forthcoming internships which constitute the second year of the MSc. Thank you Shayne and all at the V&A for making our experience such an enjoyable one. 

Alison Foster will now begin a 5-month internship at the Royal Albert Memorial Museum in Exeter, before finishing her MSc Conservation for Archaeology and Museums with a 5-month internship at the Pitt Rivers Museum, Oxford.

Nicola Harrison will also complete her MSc Conservation for Archaeology and Museums in 2013 after undertaking a 10-month internship at the Horniman Museum, London.