Jack Metcalfe and Dr. Heinrich Piening undertaking colour and dye analysis on the Chippendale writing table at Temple Newsam House.
Another feature is the virtual recolouring of the faded colours of the Chippendale pieces researched.
The technical analysis has involved the use of an technique pioneered by Dr. Heinrich Piening, Senior Furniture Conservator and Scientist, Bayerische Verwaltung der staatlischen Schlosser, Munich, whom Jack met at the conference in Sweden
Heinrich presented in Sweden a stimulating paper on his recent research into identifying dyestuffs used on antique marquetry work, without affecting the integrity of the original work. UV-VIS Spectronomy (ultra-violet, visual) is a scientific technique that produces a white light across the specimen of veneer under test, at opposing angles of 0º and 45º, for a period of 50 milliseconds, whereupon some of the white light is absorbed and some is reflected. The reflected light is detected and split by a spectrometer. This in turn produces a unique wavelength for the dye pigment lurking below the veneer surface. The wavelength can later (back at the laboratory), be run against a computer library of known dye pigments, until a matching wavelength is obtained. In layman’s language matching wavelengths against library copies can be likened to finger printing or DNA.
In February 2008 Jack arranged for Heinrich to visit Leeds to test a range of marquetry furniture made by Thomas Chippendale between 1770 -1775, held at various locations across Yorkshire. The results of those tests will be an integral part of Jack's next book, titled “Chippendale Marquetry Revealed” due for publication around mid 2011. In addition, Heinrich carried out tests on a table made by the London-based French cabinet-maker Pierre Langlois around the same period. The table, forming part of the Temple Newsam collection includes marquetry motifs of floral work together with other neo-classical musical images.
The test results matched the same dyestuffs found on furniture made by Chippendale, suggesting that both London-based workshops purchased veneers already dyed from a central source. This makes sense since the dyeing process is as specialised in its application as it is in its equipment to perform the processes, therefore making it unlikely that either furniture maker would be sufficiently geared up or knowledgeable enough to dye their own veneers. This probably holds true for the whole trade, with dyed veneers being supplied by specialists.
Some of results of the Spectronomy tests on the Langlois table are as follows.
- Acanthus leaves framing the centre panel – Indigo carmine + barberry = green
- Ribbon above the acanthus leaves – wig tree = yellow
- same as 1.
- Flower outer petals attached to ribbon Brazil + wig tree = orange
- flowers right & left of 4 – brazil = red
- music sheets – no result = plain holly - colour white
- Inside left hand trumpet – wig tree = yellow
- Outside left hand trumpet – wig tree = yellow
- sheet music - same as 6
- Harp frame – barberry = yellow
- Harp strings – brazil+ barberry = orange or reddish?
Posted by Ian Fraser