In recent years, visible and near infrared (NIR) reflectance imaging spectroscopy, i.e., the collection of contiguous calibrated spectral images to provide the reflectance spectra for each pixel of the scene, has been applied to the study of old master paintings. Its application to the study of light-sensitive works of art, such as illuminated manuscripts, has been limited to partial pigment identification using visible electronic transitions. Here we show the potential of NIR imaging spectroscopy in the 1000 to 2500 nm (10000-4000 cm~(-1)) spectral region to map and identify paint binders by utilizing vibrational features associated with methylenic, CH and amide functional groups. This is demonstrated by using a novel hyperspectral NIR imaging spectrometer (1000-2500 nm, 4.4 nm resolution) to map the use of a fat-containing paint binder (likely egg yolk) for certain compositional elements of a 15th century manuscript leaf. The use of a fat-containing binder for manuscript illumination is surprising in itself since egg white and gum Arabic (protein and polysaccharides) are historically considered to be the binders preferred by illuminators. This study offers the opportunity to map paint binders in situ on works of art, at a macroscopic scale, for the first time.
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