Old is Gold - Classic Islamic Carpets in Portugal

Between 2010 and 2011, TTT members Jessica Hallett, Raquel Santos and Catia Frade were involved in the study of three Persian carpets from the Palace of the Dukes of Bragança collection in Guimarães (Portugal). The objects’ high quality was recognized together with the advanced state of degradation, with previous interventions causing greater damage. A interdisciplinary team comprising textile conservators, art historians and conservation scientist was gathered to develop an innovative approach with surprising results.

Clockwise: Benguiat prayer rug; Duff prayer rug; Medallion carpet

In 2007 the three ‘Salting’ carpets were discovered at the Palace of the Dukes of Bragança, in city of Guimarães. Two are prayer rugs with central niches, while the third has a central medallion. Finely knotted in wool on a silk foundation, and embellished with metal threads, this is the largest collection of these carpets known outside the Topkapi Saray (Istanbul).

The term ‘Salting’ comes from the name of the famous collector, George Salting (1835-1909), who gave a notable example to the Victoria & Albert Museum in 1909, which was originally attributed to 16th-century Iran. However, the vivid colours of this and other carpets, and existence of similar examples in the Topkapi, led later historians to argue that they were Turkish rugs from the 18th or 19th centuries, and possibly even forgeries of classical Persians carpets.

This discovery was a unique opportunity not only to reflect upon the problems of origin and date, but also the advantage in the use of scientific tools to obtain responses that might be hidden on their materials. As a result analyses were conducted on fibres, dyes, mordants and metal threads used to make the three Guimarães carpets. This data was then compared with published results for related examples documented in the literature to determine whether they were 1) products of Persian or Turkish workshops, and 2) date from the classical period (16th to 17th centuries), or are later, from the 19th or even 20th centuries.

Fibres • Dyes • Metal threads

Woven structure of the carpets, showing warps, wefts, knotted pile and metal thread. Fibre analysis confirmed wool and silk in the knotted pile and foundation, and the Medallion Carpet was found to have an extremely high knot count (ca. 11,155 knots/dm2). All colours were analysed, and a more detailed study was applied to the reds. Lac-dye (Kerria spp.) was identified and as this is the predominant dye of the red ground of classical Persian carpets, it appeared to offer a possible clue to their provenance.

HPLC-DAD results of lac dye red source.

Therefore, the first High Performance Liquid Chromatography-Diode Array (HPLC-DAD) database was created for lac-dye insects (Kerriaand Paratachardinagenera) with the support of Principal Component Analyses (PCA), statistical analysis.Historical insect sources (87 samples) from the Royal Botanic Gardens, Kew (London), as well as other entomological sources, were analysed and compared with historical textile samples taken from the Guimarães carpets. These preliminary results revealed that probably the red dye is related with insect sources from Pakistan or a nearby region. Narrowing their provenance further requires more rigorous taxonomic study of the wide variety of insect species known to produce lac-dye, followed by chemical analysis and comparison with a wider range of carpets. Together, the results from all colours analysed reveal the presence of a high quality classical Persian palette.

Scanning Electronic Microscopy (SEM-EDX) revealed a distinctive method of manufacture of the metal threads, involving a hand-cut silver lamina of fine gauge covered with a gold coating and twisted around a silk core. This is consistent with the method previously proposed by some authors for the ‘Saltings’ and ‘Polonaise’ carpets. 

Weaving structure

Finally, AMS Radiocarbon dating confirmed a date between the late 15th- and mid-17th century for the Medallion Carpet, excluding the possibility of either a late date or forgery. Overall the data point to a 16th- or 17th-century date and Iran as the place of manufacture for the carpets. Moreover, the detail knowledge of the carpets’ materials attained ways to develop a responsible and effective further treatment.

Cleaning • Support • Consolidation

Medallion carpet fading (detail).

Being exhibited directly placed on the floor and without any protective surface (such as a vitrine), the carpets acquired an overall dust layer, especially in the knotted-pile surface. Widespread oxidation of the metal threads and the presence of an external dark-grey layer composed of silver corrosion products were also observed. Exhibition beneath a window, in direct sunlight and uncontrolled environmental conditions was probably the main cause for fading. Considerable material loss and fragility was observed, especially in the longitudinal and transversal axes. The partial supports were removed from the prayer rugs without any noticeable material loss. 

Duff prayer carpet, before treatment. Back side with parcel supports.

The poor condition of the three Guimarães carpets, and their exceptional value, raised several conservation challenges. Achieving physical and chemical stability and increasing their visual aesthetic were the main goals. Suction-table wet cleaning resulted in a better extraction of dirt particles, pH increase, colour improvement, and preservation of metal threads. Consolidation with hand stitches contributed to reinforce the carpets structure, as well as the use of a textile support. After conservation, several efforts were made in order to establish adequate preservation measures, such as limited exhibition time and horizontal display under a vitrine, which will allow both dust and UV light protection. Hence, the carpets could then be returned to the exhibition gallery.

The Guimarães Carpets after conservation treatment: Benguiat prayer rug; Duff prayer rug; Medallion carpet.