Optical Coherence Tomography (OCT) has been the subject of interest within the heritage science community for the over 20 years. Its potential use as monitoring tool for the conservation treatment of artworks and historical objects is well recognised. Of particular interest to this work is its abilities to give non-invasive micron scale measurements on the stratigraphy of transparent and turbid multi-layered structures such the varnish and paint layers on Old Master Paintings, enabling the monitoring of the removal of degraded varnish coatings during the cleaning process. 

In many cases, however, difficulties may arise when attempting to distinguish glazing layers on paintings (coloured, translucent layers containing pigments with refractive indices very close to the binding medium) from layers of aged varnish due to similarities in their appearance and scattering properties within OCT scans. 

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To counteract this, a combined approach has been developed, where the thickness of a discrete material layer can be assessed using OCT measurements, and then diagnostic reflectance spectra for that layer can be extracted using spectral imaging. Alongside this, the development of accompanying instrumentation to allow for the collection of OCT and spectral imaging within the same region is being undertaken, giving a direct one-to-one relationship between the two data sets recorded.