The earliest examples of the use of synthetic dyestuffs in the domain of art and conservation are still poorly documented. Here we show that the use of a database of reflectance spectra collected between 400 nm and 800 nm on pieces of dyed fabric attached in chemistry books printed at the beginning the 1870s and reference samples dyed with natural colourants, enables the non-invasive identification of the earliest artificial dyes present in these books. By applying this methodology on restored parts of the Bayeux Tapestry, it is possible to prove a major restoration of the textile artefact occurred between the years 1866 and 1872 and then to observe the very early acceptance of the use of artificial dyestuffs for the conservation of historical artefacts.

Highlights
• Hyperspectral imaging enables the non-invasive identification of the dyes used for the threads of the Bayeux Tapestry.
• Reference spectra of early synthetic dyes were recorded from chemistry books printed in the years 1870s.
• Identification of synthetic dyes shows a major restoration of the Bayeux Tapestry occurred between the years 1866 and 1872.
• This is the evidence of the early acceptance of the use of artificial dyestuffs for the conservation of historical artefacts.