A key detective technique, especially when dealing with paint, is to look at chemical composition. To maintain or restore the original appearance of an item, knowing the composition of the paint used enables conservators to perform a composition and colour match for repair.
A handheld X-ray fluorescence (XRF) spectrometer is just the tool to get the job done. This handheld machine can identify the elemental composition of different materials. This is achieved by measuring the fluorescent X-rays emitted from a sample after it has been stimulated by X-rays emitted from the handheld gun.
Paints contain an array of different elements, such as zinc, iron and titanium. Each of the elements has its own unique signature, which is like its own fingerprint. These spectrometers are used to calculate the unique peak X-ray energy released from the atoms of each element after being blasted by X-rays from the gun. These levels are then recorded as a kind of element line-up, allowing researchers to point out which ones (and how much) are present in any given sample.
This technology isn’t only used to uncover the composition of paints in a frame but also those coating historical machinery. Paul Croft, research fellow at the University of Lincoln, used the XRF spectrometer to colour match the camouflage paint covering a 1943 army tank. While studying a piece of the tank, Croft discovered a high quantity of one element in particular.
“When you understand the make up of paints you can begin to understand the pigments that were used. They were using a zinc-based paint and zinc-based primers presumably for its corrosion-preventative properties.”