Fig. 3From: Ammonium alum in alum-treated wooden artefacts: discovery, origins and consequencesATR-FTIR spectra of samples from objects 203, 206, 275 and 279 in which alum peaks dominate and show distinctive bands around 1436 cm−1 attributable to ammonium alum. Shown with ammonium alum reference (top) and lignocellulosic fraction of the 279 sample after rinsing (bottom)Back to article page