conservation

5- Drop-front Secretaire stamped by Jean-François Leleu, c.1772. Possibly made for the prince de Condé's Palais Bourbon

Conserved in 2001

The conservation project of this secretaire was short-listed for the national Pilgrim Trust Conservation Award in 2002 and was warmly praised by the judges, who concluded:

“The Leleu secretaire was the first major item to be treated using these combined methods (vacuum bag technology and a silicone heating panel in the re-gluing of decorative marquetry) and the results were impressive.”

The secretaire after conservation. Copyright The Trustees of The Wallace Collection, Inv. F301, Cat. 192.


Solvent gel cleaning of the marquetry. Drop-front marquetry before and after cleaning.


 

Extract of the text submitted to the National Pilgrim Trust Conservation Award:




The Conservation of a

French secretaire

by Jean-François Leleu, c.1772


The Wallace Collection, inventory no. F301




Introduction


This magnificent drop front secretaire, or secretaire à abattant, was made during the high point of French furniture manufacture by one of France’s greatest eighteenth century cabinet-makers, Jean-François Leleu. Although there are no surviving archives which clearly identify the patron who commissioned this extravagant piece of furniture, it is possible that the secretaire was made for the prince de Condé, whose Palais-Bourbon (now the Assemblée Nationale) was refurbished between 1772 and 1774, as it resembles surviving pieces from the Palais-Bourbon that are now on display in the Louvre. A pencilled mark J766 was found inside the secretaire during the conservation and this may, one day, help us to uncover further information about its early owners.


The secretaire has a solid oak carcase and is veneered with marquetry decoration of the finest quality comprising both exotic and indigenous woods. It is mounted with splendid bronze mounts, beautifully chased and gilded using the (nowadays banned) mercury gilding process. As its name implies, the secretaire is a receptacle of secrets, and lowering the drop front of the upper part reveals eleven drawers beneath which are hidden a further four. Using a complex mechanical device built into the piece of furniture, these four drawers rise miraculously from the lower part, to the surprise of visitors during special gallery tours.


This secretaire is a tribute to the quality of eighteenth-century craftsmanship and is both a jewel in the Wallace Collection and a source of delight to its visitors.



Pre-Conservation Condition of the Secretaire: Reasons for Conservation Work


In 1998, as part of the Collection’s rolling programme of furniture surveys, the Leleu secretaire was identified as needing conservation. There were four main areas of concern:


  1. Over time elements of the marquetry had come loose owing to the dehydration of the original adhesive. Some marquetry elements were already missing and more were at risk of becoming detached.


  1. There was a very conspicuous crack running along the centre of the drop front as well as other small cracks, one in the same drop front and one in the lower door. These cracks, as well as being very unsightly, endangered the stability of the carcase and, simultaneously, the marquetry decoration.


  1. The marquetry had become difficult to read as the existing finish had darkened with age. In addition, analyses revealed that the finish, primarily a shellac based coating, was contaminated with glycerol and linseed oil which had all cross-linked, becoming dark in appearance, whilst wax had also been applied to the surface, attracting dirt and dust. Most of these products had been applied in restorations over the preceding century, while the glycerol had unfortunately been applied without knowledge or permission by a gallery attendant in the 1970s, under the misapprehension that it would stop the wood shrinking and therefore stabilise the cracks.


  1. The gilt-bronze mounts had been lacquered during a previous restoration and with age this lacquer had perished and discoloured, giving the gold a green appearance. The degraded lacquer no longer offered any protection, exposing the mounts to the possibility of further damage, such as preferential corrosion.



Project Planning and Nature of Conservation Work


Before any treatment is carried out, it is Wallace Collection policy to compile a conservation proposal. Preparatory work included:


i. Analysis of the surface coating on the marquetry using cross-section analysis, Scanning Electron Mircrosopy (SEM), ultra-violet light inspection and photography;


ii. Detailed drawings of the marquetry decoration were made to highlight any missing elements or previous repairs. This preparatory work revealed many previous repairs to the main drop front crack that had not been noticed before. Consultation of the photographic archives revealed that these repairs pre-dated 1900.


The project was formally discussed at the Wallace Collection Conservation Advisory Panel meeting. This panel comprises of expert conservators, scientists and historians from Europe and America. The Panel inspected the secretaire and discussed various treatments and techniques that could be used to stabilise its condition. Following that meeting and the analysis, the furniture curator and the conservation department drew up a final conservation proposal. Yannick Chastang was chosen to carry out the conservation work, as he had treated another secretaire by Leleu with similar problems in 1996 whilst working at the Musée des Arts Décoratifs in Paris. Experience gained during work on the Paris piece was fundamental in planning the conservation treatment of the Wallace Collection’s secretaire.


The materials and techniques proposed for the conservation of this secretaire had all been tested previously, either on test panels or on other pieces of furniture in the collection suffering from similar problems. Many of the diverse techniques and tools used in this conservation process were specially developed in the Wallace Collection Conservation Department.


The main objectives of the conservation work was:


  1. To relay the marquetry;


  1. To remove the degraded shellac coating;

  2. To stabilise and improve the aesthetic of the split in the drop front;

  3. To re-polish the marquetry with a clear shellac based polish;

  4. To clean mounts and apply a microcrystalline wax protective coating.


It was agreed to do as little as possible with the interior of the secretaire to ensure the preservation of some of the patina, or old finish, that was visible on the secretaire prior to conservation. Although the Leleu secretaire was made during the eighteenth century, the policy is conserve objects back to 1897, the date of the bequest to the Nation of the Wallace Collection.


The Conservation Process


Conservation work began in October 2000 and was completed in April 2001.


A film of the entire conservation process was made by students from the American Intercontinental University in London, as part of their final year film-making course, and the finished twenty-minute version will be shown to museum visitors in the lecture theatre. It is planned to make a three minute version available to visitors in the Conservation Gallery.


As a first step the bronze mounts were removed and separate parts dismantled. This was carefully recorded with drawings, a mounting board showing the exact position of the screws, and video footage. Careful recording of such details enables the replacement in the same position of every screw or part after conservation but also safeguards the Collection by enabling another conservator to finish the project should the original conservator be prevented from doing so.


Re-laying of the marquetry


There are several possible approaches to the conservation of lifted marquetry. All common practices, such as the complete removal of the marquetry or the use of a spatula to introduce new glue, were considered too interventionist for this particular project. From previous experience, lifting marquetry by Leleu or his contemporaries can prove disastrous, the dyed woods used in the manufacture of marquetry during this era sometimes crumble during attempts to lift them, as a result of the acids used during the original dyeing processes. Instead, a process called re-hydration was chosen.


The ADEN conservation group (a collaboration of the Arts Décoratifs museum and the ENSTIB) developed the re-hydration technique in Paris around ten years ago. Yannick Chastang is a member of the ADEN group. It was then refined in workshops around the world including the Wallace Collection. This technique uses moisture and heat to reactivate the original glue without lifting the marquetry, water being applied on top of the marquetry and being allowed to seep through the fine cuts and cracks in the marquetry to reach the old glue underneath. As the application of too much water can cause the wood to swell, the amount of moisture applied needs to be carefully monitored and, in addition, the old degraded finish is left on the marquetry at this stage to offer some degree of protection. Once sufficient moisture has permeated the marquetry, modern glue is injected where needed. An animal glue formulation, preferred for its reversibility, was specially developed for the re-hydration technique by the ADEN group. The marquetry is then clamped and heated to exactly 65 degrees Celsius. Clamping of the marquetry was done using atmospheric pressure obtained by placing the marquetry panel in a vacuum bag without dismantling the piece, a technique specially developed in the Wallace Collection Conservation Department. Heating to a precise 65 degrees Celsius was achieved with a silicone heating sheet placed on top of the bag containing the marquetry, again a process developed in the Department for this purpose (for more details on these techniques see the attached document on innovative techniques developed by the Wallace Collection).


Cleaning of the marquetry


Removing existing finish on historical objects is always subject to discussion and careful consideration. However, historical evidence of original finishes, the previous repair history of the object and analyses showed that the pre-conservation finish on this secretaire was unlikely to be original and, in addition, this old finish no longer offered any protection to the marquetry. There were also fears that the various pollutants applied during previous restorations and mistreatments to the surface of the marquetry could migrate into the original eighteenth-century marquetry and become irreversible. The existing polish was therefore removed.


As an alternative to traditional cleaning methods, which had proved unsuccessful in earlier attempts made during the 1980s, the Wallace Collection has refined the use of a water and solvent gel system. This technique was developed for picture conservation and was pioneered in America by Professor Richard Wolbers and his colleague Gregory Landrey. Since 1996 the Wallace Collection has used its own version of this process to clean marquetry. The main property of the gel is to dissolve, then absorb, the pollutants that sit on top obscuring the marquetry, limiting the risk of the pollutant sinking into the marquetry and causing irreversible damage. Concerns are often expressed that this technique may remove some of the original dyes in the wood marquetry. However, because most dyes used in the eighteenthcentury are not pure colour dyes injected into the wood (as in the nineteenth century), but are more often the result of a chemical reaction between wood chemicals and an acid, the dyed woods are very stable and resistant to gel cleaning.


The cleaning of the Leleu secretaire marquetry revealed many previously unsuspected colours and details. The marble top effect at the bottom of the trophy design on the drop front marquetry was particularly successful; as was the yellow of the brass and the dyed grey wood of the steel components of the compass depicted there. Unfortunately cleaning can only do so much, since most of the original wood colour had been discoloured irreversibly by sunlight.

Repair of the crack


After re-hydration, the crack in the lower door closed and did not need further work.


The unsightly crack in the drop front had undergone previous restoration involving the removal of original wood and the insertion of new pieces of marquetry. Dust and unsightly in-fills were removed from inside the crack. It was then filled with new balsa wood, which is soft enough to ensure that any future shrinkage of the wood would happen in the same place and not result in a new crack elsewhere.

Missing pieces of the marquetry were re-cut using the matching wood species and coloured, using heat treatment and watercolour paints. The location of the new pieces has been recorded in the conservation report. The crack in the veneer was filled with coloured wax.


Although the crack is now stable and less conspicuous, it is still visible. The dull properties of the wax do not match the richness of the wood, in particular the rippling effect of the sycamore grain. However, this treatment is fully reversible and less interventionist, compared to the alternative proposal of removing the marquetry above the crack and regluing it in a lower position, thereby eliminating the gap.


Polishing the marquetry


Although marquetry may have been originally waxed in the eighteenth century, nineteenth-century fashion was for polish. Polish offers better protection against possible scratches and new pollutants, factors which need to be considered when a piece is on public display. Layers of clear polish made of shellac and copal resin were applied with a rubber on top of the marquetry. The high shine of the new polish was dulled down with a smooth sanding and the application of beeswax, which gives the aspect of a wax finish and harmonises with other pieces of furniture on display in the Collection.


Cleaning of the mounts


During the cleaning of the Wallace Collection’s staircase balustrade in 1995 a study was done in order to find the best possible solvent to remove the perished lacquer on top of the gilded mounts. Diacetone alcohol has since been used with the mounts being soaked in the solvent for several days.


For the first time, the bronze mounts of the Leleu secretaire were all cleaned of their protective lacquer using fumes of diacetone alcohol. The bronze mounts have to be left exposed to the fumes longer than if they were soaked in a bath of the product, however this method ensures the preservation of the back patina of the bronze mounts. It is also a more economical and environmentally friendly technique as it uses less diacetone alcohol.


The gilding layer was in particularly good condition, so the decision was taken to wax the mounts with micro-crystalline wax and not to lacquer them.


Documenting the Work


Following the conservation treatment a full conservation report was written, which included detailed photographs taken at every stage of conservation.

Innovative Practices


This treatment used five innovative and minimum interventionist techniques:


1. Re-hydration of the original glue to stabilise the decorative surface;

  1. The vacuum bag, to relay the marquetry;


3. The silicone heating sheet, developed in our own department, giving far greater control over surface temperature when re-heating the glue;

4. Gel cleaning systems, to effectively remove surface coatings without the pollutants being absorbed into the decorative surface;

5. The cleaning of the mounts using solvent fumes.


All these techniques have been widely demonstrated in the Wallace Collection workshop to conservation colleges, conservation professionals and to art history students. Despite initial investment, economies have been made, both in time and money, and the new techniques have provided better results, more in keeping with the modern ethics of conservation.


Communication with the Wider Public


The new Conservation Gallery, which opened as part of the Wallace Collection Centenary Project in 2000, offers the Department a unique opportunity to display recent conservation projects and discoveries. The gallery opened with a display about the gel cleaning technique. The video produced with the American Intercontinental University will be a great tool for the future. Aimed at the general public, it was filmed and edited by students who were not experts in conservation and who had to overcome the difficulty of making this “science” of conservation more accessible to a wide audience.


The opportunity to work on a day-to-day basis with superb pieces, like the Leleu secretaire, reveals insights into and information about the working practices of the greatest eighteenth-century craftsmen. New discoveries during the repair included a mark, as well as evidence of mistakes and changes of mind by the original maker. This new information was published in the first ever exhibition on marquetry, Paintings in Wood: The Hidden Colours of French Marquetry (October 2001 to January 2002), which proved a great success and of which the Leleu secretaire was one of the major exhibits.


The aim of the Wallace Collection workshops is to continue conserving these important works of art for future generations, but also to push forward the frontiers of knowledge in conservation and in materials and techniques of the past. Conservation is always a learning curve. As a public institution we have a duty, and even a priority, to share our knowledge with others.