Conservation around the Millennium (Hungarian National Museum, 2001)
Pages - 125
EXPERIMENT ON COMPUTERISED COLOUR RECONSTRUCTION OF THE CORRODED METAL SURFACES OF TEXTILES ORNAMENTS WITH LEATHER, PAPER OR MEMBRANE THREADS Márta Járó, György T. Nagy INTRODUCTION We can sometimes find so-called combined metal threads on medieval and sometimes later fabrics and embroidery. They are leather, paper or membrane, gold or silver threads. Leather gold and silver threads are thin strips coated with gold foil or dust or with silver foil. Sometimes they are wound around a fibrous core, which is usually silk, cotton, rarely linen thread. Strips cut from metal coated parchment (or vellum) belong here as well. Paper gold or silver threads were usually made in the following way: paper was coated generally with red or white bolus or pigment mixed with adhesive and the resulting smooth surface covered with gold or silver foil, sometimes with gilt silver foil or with tin foil to imitate silver. Both the narrow strips cut from metal coated paper and the varieties wound around a fibrous core (mainly silk) were used. Paper gold or silver threads have been used first of all in the Far East to ornament textiles. Membrane gold or silver threads are narrow strips cut from metal coated animal membrane and wound around a fibrous core (according to the analyses of linen thread). In this case gilt silver or silver foil covers the organic support. By now, except for some of the leather and paper gold threads, the surfaces of the combined threads have become strongly worn. The remaining metal darkened, became iridescent and in most of the cases totally blackened. This can be the reason why these threads, except for the paper threads, were used only for a few hundred years. The metal threads made from solid silver or gilt silver (or other metals) replaced them from about the 15-16th centuries. It is often difficult to determine in the case of textiles ornamented with corroded combined metal threads if the thread was originally gold or silver coloured. At technical descriptions we can often find different determinations of thread at similar items. The fragments of the textile illustrated in picture 8, for example, can be found in several collections. The crescent moons were woven with membrane thread into the textile. Markowsky mentions gold-coated membrane in the Cologne catalogue (1), while von Wilckens determines the metal thread as silver-coated membrane (2) in the Berlin catalogue. In the case of the fabric in picture 10, it is also difficult to decide with bare eyes if the metal threads in the weaving were originally gold or silver coloured. Our aim was to attempt the reconstruction of the original view of the surfaces with metal threads with the help of the results of visual examinations and scientific analyses. CAUSES OF THE DETERIORATION OF TEXTILES ORNAMENTED WITH COMBINED METAL THREADS Leather, paper and membrane threads wear off since the extremely thin metal layer, usually thinner than one thousandth of a millimetre (1 pm), is easily 125
