We have a portable X-Ray Fluorescence analyser that allows us to undertake non-destructive analysis of metals and alloys or other materials containing metal compounds such as textiles, drawings and paint. Analysis is fast and can be carried out in the studio, outdoors or at the client’s premises. The data from the analysis is stored in the machine’s PDA then downloaded onto computer for alloy comparison and report production.
The XRF is highly accurate, can identify very small traces of metallic elements within an alloy and can be used on any metal object or configured using the lab stand to analyse minute samples. The speed of the machine, with normal exposures of around 30 seconds, allows many objects or samples to be analysed in one day. By taking multiple readings we can produce both an average alloy composition for each object and a detailed report specifying the exact alloy components of various parts of each sculpture.
The ability to quickly identify alloys for comparison against samples with known provenance or, for instance, identify residual mercury in fire gilding or traces of past plating, allows us to advise clients at the time of inspection of sometimes critical technical information that may influence conservation treatment.
To aid art historical research, analysis may help identify the date of manufacture, past restorations or surface treatments, when combined with other technical and curatorial information. The cost of undertaking an analysis and producing a report is totally dependant on the time required to undertake the work and the location of the objects to be tested.
We carried out a detailed inspection of the dial section of the astronomical clock at Hampton Court Palace.
XRF analysis helped us to establish the coatings and underlying metals that form the substrate to the dial, which are copper sheet dipped in a lead-tin alloy (90:10), riveted with copper rivets to a wrought iron structure.
This data informed our conservation proposal for the most appropriate treatment of the object.
While it was undergoing restoration on site at Stourhead, we were asked to attend to carry out analysis on the metal components on this cabinet.
We were able to establish, for example, the presence of silver foil backing beneath the stone inlays, (illustrated in the detail below), and confirm the presence of mercury gilding on other metalwork elements.