Conservation around the Millennium (Hungarian National Museum, 2001)

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If visual observation does not give results, gilding can appear with untwisting a thickened thread sample (where the strip fragments - for joining them - are wound one over the another).

In most of the cases, however, scientific methods, instrumental analyses are necessary to determine if the surfaces that turned into black or grey had originally been gold or silver coloured, or if the two colours had been used side by side. Electron beam microanalysis or X-ray fluorescent analyses, which are world-wide used for the analysis of metal threads, can be suitable for this purpose (3). The analysis of a microscopic, 1-2 mm long, strip covered with black corrosion product can reveal the composition of the metal and if it contains gold or not (picture 3-4).

At the evaluation of the analytical results, several factors must be considered (4), and if we cannot identify gold beside silver, more samples must be analysed to get a correct result (it is, namely, possible, that the gold was totally worn off from the surface of the sample).

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3. Blackened membrane thread. Spectrum from the surface made with electron beam microanalysis. Aluminium, silicon, gold, sulphur, chlorine and silver can be identified in the metal layer.

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4. Blackened paper thread. Spectrum from the surface made with electron beam microanalysis3. Tin can be identified in the metal layer.

RECONSTRUCTION OF THE "ORIGINAL" METAL COLOURS - POSSIBILITY TO REMOVE THE CORROSION

The cleaning of the blackened and grey metal surfaces and the “restoration” of the original silver or gold colour are impossible in the case of combined metal threads. Even the finest mechanic cleaning can eliminate the metal layer from the surface. The same happens if we try to dissolve chemically the corrosion (picture 5).

Consequently, unlike at other silver or gilt silver objects, the blackened combined metal threads cannot be restored. Not even an approximation of the so-called original state and colouring can be reached.

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