Lost writing uncovered by laser two-photon fluorescence provides a terminus post quem for Roman colonization of Hispania Citerior

In this work, two-photon absorption fluorescence is used as a non-destructive method to detect the presence of paint upon an archaeological sample. The objective was to recover writing that, due to the discoloration caused by the passage of the time, was barely readable. The technique has been successfully applied to determine the consular date painted upon the neck of a Dressel 1A amphora found in the Roman village of Iesso (Guissona), in Catalonia. The identification of the consular date provides a terminus post quem for the foundation date for the city as well as a starting date for the Roman colonization of Hispania Citerior.