Identifying the components of paper, inks and varnishes in samples of 19TH and 20TH century school maps using non-invasive analytical techniques FTIR-ATR and XRF

Abstract

School maps from the 19th and 20th centuries are a very interesting heritage typology, but they have received little social or cultural recognition. Due to the poor quality of the composition materials of these documents and a lack of concern for studying and safeguarding them, surviving examples are in a deplorable state of preservation. The purpose of this investigation is to characterise 19th and 20th century school maps as a way to optimise interventions by conservator-restorers. The aim is to study a selection of maps from the University of Granada Archive (Granada, Spain) by collecting microsamples and applying two non-invasive analytical techniques: Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (FTIR-ATR) and X-Ray Fluorescence (XRF). The FTIR results identified the paper components: calcium carbonate (875 cm−1), kaolin (910 and 758 cm−1), and calcium sulphate, which has a band coinciding with alum (665 cm−1). They also confirmed the use of starch (1145 and 1075 cm−1). XRF detected iron and chlorine, associated with sheet formation and bleaching. The FTIR spectra of the printing identified the binder linseed oil (2920 and 2850 cm−1) and the pigment Prussian blue (2090 cm−1), and XRF confirmed the use of chrome yellow (Pb, Cr) or zinc yellow (Zn, Cr), vermillion (Hg, S) and barite (Ba). The varnish used as protection was not identifiable by FTIR due to the thickness and/or poor state of preservation of the layer. Dammar resin was detected in only two maps.