Investigation of a medieval Spanish altar ‘set’
The group of liturgical furnishings (objects used in a
religious ceremony) known as the Vera Cruz altar set was conserved
for display in the Medieval Europe gallery at the British Museum
and investigated to find out how old it is and how it
was made. The conservation treatment aimed to clean and bring
out the shine of the metal surface and to achieve this an old
protective coating and tarnish were removed.
As part of the investigation, the technical characteristics of the objects were recorded and scientific analyses of them was carried out. Observations on construction, materials and tool marks suggest that many of the pieces have been repaired and changes have been made to the original elements.
The pieces are made from sheet silver, which has been hammered into shape, with some additional cast elements. The components are completely or partially gilded with further decorations of champleve and basse-taille enamel, niello (an inlay of metal sulphides) and coloured organic infill. The construction of some of the pieces and the presence of low melting temperature soft solders of tin and lead show that they were repaired in the past.
The composition of the enamel on the applied plaques was analysed using X-ray fluorescence. This method detected chromium, a green colorant only used in the nineteenth century or later, and a glass composition dominated by lead and potassium (as potash) in a few of the enamels. In other areas of enamel, the compositions were consistent with manufacture during the Medieval period.
Although the analysis cannot tell us exactly when the individual items were made, it does confirm that there is Medieval enamel on the pieces. It also tells us that a significant amount of the enamelling we see today, and the associated repairs, were carried out in the nineteenth century.