Raman study of synthetic organic pigments and dyes in early lithographic inks (1890-1920)

The colorants and additives present in lithographic inks used in a group of posters manufactured during the period between 1890 and 1920, an extremely fruitful period regarding the development of the synthetic dye and pigment industry, were identified by Raman spectroscopy. Synthetic organic pigments and dyes were detected along with inorganic pigments. Red, blue and yellow synthetic organic pigments were more frequently observed in posters manufactured by the end of the 1890-1920 period, reflecting that lithographers were actively experimenting to achieve hues not accessible using inorganic pigments alone. The water-sensitivity of the inks containing synthetic organic colorants is discussed in relation to the potential application of aqueous conservation treatments to early posters. Copyright (C) 2006 John Wiley & Sons, Ltd.