BCD 2019

164 T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 1 9 C AT H E D R A L C O MM U N I C AT I O N S a much greater degree of intervention is sometimes required to avoid the loss of the object’s architectural and artistic significance, particularly when it forms a key element of an important historic interior. Fortunately, where scagliola is concerned, most defects can be successfully repaired by capable and experienced hands, restoring the integrity of the original and allowing the intention of the artist to be fully appreciated. Detailed below are three very different conservation/ restoration projects which together illustrate some of the more common challenges faced by conservators. Each poses a complex set of issues that were solved through a combination of experience, dedication, passion and love for the art of scagliola. BUCKINGHAM PALACE An unusual and rather unique problem which was drawn to our attention many years ago related to pioneering regency work in the state rooms at Buckingham Palace by scagliolist Joseph Browne for the architect John Nash. These included a series of spectacular three- quarter round pilasters in the music room which appeared to have been cut from solid lapis lazuli gemstone, and similar pilasters in the blue room which were originally a vivid crimson. The latter, however, had been painted over soon after installation to imitate a rather dull brown onyx, as the original colour had been deemed too rich for the taste of the time. As Thomas Creevey, an English politician, commented in May 1835: ‘…the costly ornaments of the state rooms exceeded all belief in their bad taste and every species of infirmity. Raspberry-coloured pillars without end that quite turn you sick to look at…’. Unfortunately, the fine surfaces of the pilasters in both rooms had been slowly deteriorating for decades, and the problems had been accelerating during the later years, mainly due to public access to the state rooms, inadvertently introducing excess amounts of condensation. By now the beautiful surfaces of the columns had become pitted, had lost their original beauty and subtlety and it was suspected that this was a direct result of Joseph Browne inserting metal filings in the scagliola matrix to create a more convincing lapis effect. Visually, this was highly successful and Browne also used metal filings in the bright crimson columns of the blue room, creating a somewhat ‘fantasy’ finish not reminiscent of any familiar marble or stone. So, after an initial visit and visual assessment of the problem, samples were extracted from inconspicuous areas of both sets of pilasters. These were carefully analysed with a view to determining the causes of the problem and, most importantly, to assess whether a restoration programme was feasible. This in-depth investigation concentrated on the lapis pilasters in the music room and a sample of approximately 10 x 10cm was taken for analysis, to provide information on the pigments, coatings, aggregates, additives and filings that Browne had used. Alongside chemical and physical analyses, samples were sent to Leeds University laboratory for analysis by scanning with an electron microscope using energy-dispersive X-ray (EDX) spectroscopy. The analyses revealed that the pigment used was an early Prussian blue, readily available at the time for the most prestigious work. However, the ratio of pigment to plaster was found to be about 1:5 by volume, which would have rendered the scagliola mix rather weak. This would have probably compounded problems caused by the metal filings, which were discovered to be shavings of tin, copper and brass, all non-ferrous, anything from a few microns to 4mm in length, averaging 2mm each. Many other particles and impurities were detected, but these were all naturally occurring in the sort of plaster used at the time, and generally made the matrix more robust. The coating was, as expected, oxidised linseed oil. So, the verdict was that the pitting was due to oxidisation of the tip of the metal particles that came into contact with the air, expanding, thus weakening the scagliola matrix around them. Although a small amount of corrosion had also formed around the metal particles this would have only taken place once, just after the installation of the pilasters, and was now stable within the body of plaster. The solution to this problem and in order to delay or even halt this ongoing process, was to create a barrier between the metal filings and the atmosphere. This barrier in the form of microcrystalline wax would prevent any moisture from further reacting with the metal filings and would also act as a soft polish, which would need re-applying from time to time. A restoration programme was then drawn up by the author and the company’s conservator Yvonne Adamson, based on the unique investigation and findings of the The sample extracted from the blue room: the metal filings, current paint coating and the bright crimson colour are clearly evident The author working on the sample area in 2001 The same sample area during a second site visit in 2008